Remove io::Result from syntax::print

Since we're now writing directly to the vector, there's no need to
thread results through the whole printing infrastructure

5 files changed, 1088 insertions, 1170 deletions

diff --git a/src/libsyntax/mut_visit.rs b/src/libsyntax/mut_visit.rs
index e23bc025f6e..11a1de13fc2 100644
--- a/src/libsyntax/mut_visit.rs
+++ b/src/libsyntax/mut_visit.rs
@@ -1261,7 +1261,6 @@ pub fn noop_visit_vis<T: MutVisitor>(Spanned { node, span }: &mut Visibility, vi
 
 #[cfg(test)]
 mod tests {
-    use std::io;
     use crate::ast::{self, Ident};
     use crate::util::parser_testing::{string_to_crate, matches_codepattern};
     use crate::print::pprust;
@@ -1271,7 +1270,7 @@ mod tests {
 
     // this version doesn't care about getting comments or docstrings in.
     fn fake_print_crate(s: &mut pprust::State<'_>,
-                        krate: &ast::Crate) -> io::Result<()> {
+                        krate: &ast::Crate) {
         s.print_mod(&krate.module, &krate.attrs)
     }
 
diff --git a/src/libsyntax/parse/diagnostics.rs b/src/libsyntax/parse/diagnostics.rs
index 0ea0b2a694d..edcdb18a037 100644
--- a/src/libsyntax/parse/diagnostics.rs
+++ b/src/libsyntax/parse/diagnostics.rs
@@ -613,12 +613,12 @@ impl<'a> Parser<'a> {
                 let sum_with_parens = pprust::to_string(|s| {
                     use crate::print::pprust::PrintState;
 
-                    s.s.word("&")?;
-                    s.print_opt_lifetime(lifetime)?;
-                    s.print_mutability(mut_ty.mutbl)?;
-                    s.popen()?;
-                    s.print_type(&mut_ty.ty)?;
-                    s.print_type_bounds(" +", &bounds)?;
+                    s.s.word("&");
+                    s.print_opt_lifetime(lifetime);
+                    s.print_mutability(mut_ty.mutbl);
+                    s.popen();
+                    s.print_type(&mut_ty.ty);
+                    s.print_type_bounds(" +", &bounds);
                     s.pclose()
                 });
                 err.span_suggestion(
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index fc206580e38..3143f2b9971 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -2572,12 +2572,12 @@ impl<'a> Parser<'a> {
                           };
                           let sugg = pprust::to_string(|s| {
                               use crate::print::pprust::PrintState;
-                              s.popen()?;
-                              s.print_expr(&e)?;
-                              s.s.word( ".")?;
-                              s.print_usize(float.trunc() as usize)?;
-                              s.pclose()?;
-                              s.s.word(".")?;
+                              s.popen();
+                              s.print_expr(&e);
+                              s.s.word( ".");
+                              s.print_usize(float.trunc() as usize);
+                              s.pclose();
+                              s.s.word(".");
                               s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
                           });
                           err.span_suggestion(
@@ -4634,9 +4634,9 @@ impl<'a> Parser<'a> {
                     }
                     let sugg = pprust::to_string(|s| {
                         use crate::print::pprust::{PrintState, INDENT_UNIT};
-                        s.ibox(INDENT_UNIT)?;
-                        s.bopen()?;
-                        s.print_stmt(&stmt)?;
+                        s.ibox(INDENT_UNIT);
+                        s.bopen();
+                        s.print_stmt(&stmt);
                         s.bclose_maybe_open(stmt.span, INDENT_UNIT, false)
                     });
                     e.span_suggestion(
diff --git a/src/libsyntax/print/pp.rs b/src/libsyntax/print/pp.rs
index 4f721e9f92f..f64e95aee5b 100644
--- a/src/libsyntax/print/pp.rs
+++ b/src/libsyntax/print/pp.rs
@@ -136,7 +136,6 @@
 
 use std::collections::VecDeque;
 use std::fmt;
-use std::io;
 use std::borrow::Cow;
 use log::debug;
 
@@ -311,16 +310,15 @@ impl<'a> Printer<'a> {
         self.buf[self.right].token = t;
     }
 
-    fn pretty_print_eof(&mut self) -> io::Result<()> {
+    fn pretty_print_eof(&mut self) {
         if !self.scan_stack.is_empty() {
             self.check_stack(0);
-            self.advance_left()?;
+            self.advance_left();
         }
         self.indent(0);
-        Ok(())
     }
 
-    fn pretty_print_begin(&mut self, b: BeginToken) -> io::Result<()> {
+    fn pretty_print_begin(&mut self, b: BeginToken) {
         if self.scan_stack.is_empty() {
             self.left_total = 1;
             self.right_total = 1;
@@ -334,24 +332,22 @@ impl<'a> Printer<'a> {
         self.buf[self.right] = BufEntry { token: Token::Begin(b), size: -self.right_total };
         let right = self.right;
         self.scan_push(right);
-        Ok(())
     }
 
-    fn pretty_print_end(&mut self) -> io::Result<()> {
+    fn pretty_print_end(&mut self) {
         if self.scan_stack.is_empty() {
             debug!("pp End/print Vec<{},{}>", self.left, self.right);
-            self.print_end()
+            self.print_end();
         } else {
             debug!("pp End/buffer Vec<{},{}>", self.left, self.right);
             self.advance_right();
             self.buf[self.right] = BufEntry { token: Token::End, size: -1 };
             let right = self.right;
             self.scan_push(right);
-            Ok(())
         }
     }
 
-    fn pretty_print_break(&mut self, b: BreakToken) -> io::Result<()> {
+    fn pretty_print_break(&mut self, b: BreakToken) {
         if self.scan_stack.is_empty() {
             self.left_total = 1;
             self.right_total = 1;
@@ -367,25 +363,24 @@ impl<'a> Printer<'a> {
         self.scan_push(right);
         self.buf[self.right] = BufEntry { token: Token::Break(b), size: -self.right_total };
         self.right_total += b.blank_space;
-        Ok(())
     }
 
-    fn pretty_print_string(&mut self, s: Cow<'static, str>, len: isize) -> io::Result<()> {
+    fn pretty_print_string(&mut self, s: Cow<'static, str>, len: isize) {
         if self.scan_stack.is_empty() {
             debug!("pp String('{}')/print Vec<{},{}>",
                    s, self.left, self.right);
-            self.print_string(s, len)
+            self.print_string(s, len);
         } else {
             debug!("pp String('{}')/buffer Vec<{},{}>",
                    s, self.left, self.right);
             self.advance_right();
             self.buf[self.right] = BufEntry { token: Token::String(s, len), size: len };
             self.right_total += len;
-            self.check_stream()
+            self.check_stream();
         }
     }
 
-    crate fn check_stream(&mut self) -> io::Result<()> {
+    crate fn check_stream(&mut self) {
         debug!("check_stream Vec<{}, {}> with left_total={}, right_total={}",
                self.left, self.right, self.left_total, self.right_total);
         if self.right_total - self.left_total > self.space {
@@ -396,12 +391,11 @@ impl<'a> Printer<'a> {
                 let scanned = self.scan_pop_bottom();
                 self.buf[scanned].size = SIZE_INFINITY;
             }
-            self.advance_left()?;
+            self.advance_left();
             if self.left != self.right {
-                self.check_stream()?;
+                self.check_stream();
             }
         }
-        Ok(())
     }
 
     crate fn scan_push(&mut self, x: usize) {
@@ -431,7 +425,7 @@ impl<'a> Printer<'a> {
         assert_ne!(self.right, self.left);
     }
 
-    crate fn advance_left(&mut self) -> io::Result<()> {
+    crate fn advance_left(&mut self) {
         debug!("advance_left Vec<{},{}>, sizeof({})={}", self.left, self.right,
                self.left, self.buf[self.left].size);
 
@@ -449,7 +443,7 @@ impl<'a> Printer<'a> {
                 _ => 0
             };
 
-            self.print(left, left_size)?;
+            self.print(left, left_size);
 
             self.left_total += len;
 
@@ -462,8 +456,6 @@ impl<'a> Printer<'a> {
 
             left_size = self.buf[self.left].size;
         }
-
-        Ok(())
     }
 
     crate fn check_stack(&mut self, k: isize) {
@@ -494,12 +486,11 @@ impl<'a> Printer<'a> {
         }
     }
 
-    crate fn print_newline(&mut self, amount: isize) -> io::Result<()> {
+    crate fn print_newline(&mut self, amount: isize) {
         debug!("NEWLINE {}", amount);
         self.out.push('\n');
         self.pending_indentation = 0;
         self.indent(amount);
-        Ok(())
     }
 
     crate fn indent(&mut self, amount: isize) {
@@ -517,7 +508,7 @@ impl<'a> Printer<'a> {
         }
     }
 
-    crate fn print_begin(&mut self, b: BeginToken, l: isize) -> io::Result<()> {
+    crate fn print_begin(&mut self, b: BeginToken, l: isize) {
         if l > self.space {
             let col = self.margin - self.space + b.offset;
             debug!("print Begin -> push broken block at col {}", col);
@@ -532,52 +523,46 @@ impl<'a> Printer<'a> {
                 pbreak: PrintStackBreak::Fits
             });
         }
-        Ok(())
     }
 
-    crate fn print_end(&mut self) -> io::Result<()> {
+    crate fn print_end(&mut self) {
         debug!("print End -> pop End");
         let print_stack = &mut self.print_stack;
         assert!(!print_stack.is_empty());
         print_stack.pop().unwrap();
-        Ok(())
     }
 
-    crate fn print_break(&mut self, b: BreakToken, l: isize) -> io::Result<()> {
+    crate fn print_break(&mut self, b: BreakToken, l: isize) {
         let top = self.get_top();
         match top.pbreak {
             PrintStackBreak::Fits => {
                 debug!("print Break({}) in fitting block", b.blank_space);
                 self.space -= b.blank_space;
                 self.indent(b.blank_space);
-                Ok(())
             }
             PrintStackBreak::Broken(Breaks::Consistent) => {
                 debug!("print Break({}+{}) in consistent block",
                        top.offset, b.offset);
-                let ret = self.print_newline(top.offset + b.offset);
+                self.print_newline(top.offset + b.offset);
                 self.space = self.margin - (top.offset + b.offset);
-                ret
             }
             PrintStackBreak::Broken(Breaks::Inconsistent) => {
                 if l > self.space {
                     debug!("print Break({}+{}) w/ newline in inconsistent",
                            top.offset, b.offset);
-                    let ret = self.print_newline(top.offset + b.offset);
+                    self.print_newline(top.offset + b.offset);
                     self.space = self.margin - (top.offset + b.offset);
-                    ret
                 } else {
                     debug!("print Break({}) w/o newline in inconsistent",
                            b.blank_space);
                     self.indent(b.blank_space);
                     self.space -= b.blank_space;
-                    Ok(())
                 }
             }
         }
     }
 
-    crate fn print_string(&mut self, s: Cow<'static, str>, len: isize) -> io::Result<()> {
+    crate fn print_string(&mut self, s: Cow<'static, str>, len: isize) {
         debug!("print String({})", s);
         // assert!(len <= space);
         self.space -= len;
@@ -592,11 +577,9 @@ impl<'a> Printer<'a> {
         self.out.extend(std::iter::repeat(' ').take(self.pending_indentation as usize));
         self.pending_indentation = 0;
         self.out.push_str(&s);
-
-        Ok(())
     }
 
-    crate fn print(&mut self, token: Token, l: isize) -> io::Result<()> {
+    crate fn print(&mut self, token: Token, l: isize) {
         debug!("print {} {} (remaining line space={})", token, l,
                self.space);
         debug!("{}", buf_str(&self.buf,
@@ -609,7 +592,7 @@ impl<'a> Printer<'a> {
             Token::Break(b) => self.print_break(b, l),
             Token::String(s, len) => {
                 assert_eq!(len, l);
-                self.print_string(s, len)
+                self.print_string(s, len);
             }
             Token::Eof => panic!(), // Eof should never get here.
         }
@@ -618,7 +601,7 @@ impl<'a> Printer<'a> {
     // Convenience functions to talk to the printer.
 
     /// "raw box"
-    crate fn rbox(&mut self, indent: usize, b: Breaks) -> io::Result<()> {
+    crate fn rbox(&mut self, indent: usize, b: Breaks) {
         self.pretty_print_begin(BeginToken {
             offset: indent as isize,
             breaks: b
@@ -626,49 +609,49 @@ impl<'a> Printer<'a> {
     }
 
     /// Inconsistent breaking box
-    crate fn ibox(&mut self, indent: usize) -> io::Result<()> {
+    crate fn ibox(&mut self, indent: usize) {
         self.rbox(indent, Breaks::Inconsistent)
     }
 
     /// Consistent breaking box
-    pub fn cbox(&mut self, indent: usize) -> io::Result<()> {
+    pub fn cbox(&mut self, indent: usize) {
         self.rbox(indent, Breaks::Consistent)
     }
 
-    pub fn break_offset(&mut self, n: usize, off: isize) -> io::Result<()> {
+    pub fn break_offset(&mut self, n: usize, off: isize) {
         self.pretty_print_break(BreakToken {
             offset: off,
             blank_space: n as isize
         })
     }
 
-    crate fn end(&mut self) -> io::Result<()> {
+    crate fn end(&mut self) {
         self.pretty_print_end()
     }
 
-    pub fn eof(&mut self) -> io::Result<()> {
+    pub fn eof(&mut self) {
         self.pretty_print_eof()
     }
 
-    pub fn word<S: Into<Cow<'static, str>>>(&mut self, wrd: S) -> io::Result<()> {
+    pub fn word<S: Into<Cow<'static, str>>>(&mut self, wrd: S) {
         let s = wrd.into();
         let len = s.len() as isize;
         self.pretty_print_string(s, len)
     }
 
-    fn spaces(&mut self, n: usize) -> io::Result<()> {
+    fn spaces(&mut self, n: usize) {
         self.break_offset(n, 0)
     }
 
-    crate fn zerobreak(&mut self) -> io::Result<()> {
+    crate fn zerobreak(&mut self) {
         self.spaces(0)
     }
 
-    pub fn space(&mut self) -> io::Result<()> {
+    pub fn space(&mut self) {
         self.spaces(1)
     }
 
-    pub fn hardbreak(&mut self) -> io::Result<()> {
+    pub fn hardbreak(&mut self) {
         self.spaces(SIZE_INFINITY as usize)
     }
 
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index b3bb9123a48..88f96fc8483 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -21,7 +21,7 @@ use syntax_pos::{self, BytePos};
 use syntax_pos::{DUMMY_SP, FileName};
 
 use std::borrow::Cow;
-use std::io::{self, Read};
+use std::io::Read;
 use std::vec;
 
 pub enum AnnNode<'a> {
@@ -35,8 +35,8 @@ pub enum AnnNode<'a> {
 }
 
 pub trait PpAnn {
-    fn pre(&self, _state: &mut State<'_>, _node: AnnNode<'_>) -> io::Result<()> { Ok(()) }
-    fn post(&self, _state: &mut State<'_>, _node: AnnNode<'_>) -> io::Result<()> { Ok(()) }
+    fn pre(&self, _state: &mut State<'_>, _node: AnnNode<'_>) { }
+    fn post(&self, _state: &mut State<'_>, _node: AnnNode<'_>) { }
 }
 
 #[derive(Copy, Clone)]
@@ -77,7 +77,7 @@ pub fn print_crate<'a>(cm: &'a SourceMap,
                        input: &mut dyn Read,
                        out: &mut String,
                        ann: &'a dyn PpAnn,
-                       is_expanded: bool) -> io::Result<()> {
+                       is_expanded: bool) {
     let mut s = State::new_from_input(cm, sess, filename, input, out, ann, is_expanded);
 
     if is_expanded && std_inject::injected_crate_name().is_some() {
@@ -91,16 +91,16 @@ pub fn print_crate<'a>(cm: &'a SourceMap,
         let list = attr::mk_list_item(
             DUMMY_SP, ast::Ident::with_empty_ctxt(sym::feature), vec![pi_nested]);
         let fake_attr = attr::mk_attr_inner(DUMMY_SP, attr::mk_attr_id(), list);
-        s.print_attribute(&fake_attr)?;
+        s.print_attribute(&fake_attr);
 
         // #![no_std]
         let no_std_meta = attr::mk_word_item(ast::Ident::with_empty_ctxt(sym::no_std));
         let fake_attr = attr::mk_attr_inner(DUMMY_SP, attr::mk_attr_id(), no_std_meta);
-        s.print_attribute(&fake_attr)?;
+        s.print_attribute(&fake_attr);
     }
 
-    s.print_mod(&krate.module, &krate.attrs)?;
-    s.print_remaining_comments()?;
+    s.print_mod(&krate.module, &krate.attrs);
+    s.print_remaining_comments();
     s.s.eof()
 }
 
@@ -134,14 +134,14 @@ impl<'a> State<'a> {
 }
 
 pub fn to_string<F>(f: F) -> String where
-    F: FnOnce(&mut State<'_>) -> io::Result<()>,
+    F: FnOnce(&mut State<'_>),
 {
     let mut wr = String::new();
     {
         let ann = NoAnn;
         let mut printer = rust_printer(&mut wr, &ann);
-        f(&mut printer).unwrap();
-        printer.s.eof().unwrap();
+        f(&mut printer);
+        printer.s.eof();
     }
     wr
 }
@@ -364,20 +364,20 @@ pub fn fun_to_string(decl: &ast::FnDecl,
                      generics: &ast::Generics)
                      -> String {
     to_string(|s| {
-        s.head("")?;
+        s.head("");
         s.print_fn(decl, header, Some(name),
-                   generics, &source_map::dummy_spanned(ast::VisibilityKind::Inherited))?;
-        s.end()?; // Close the head box
-        s.end() // Close the outer box
+                   generics, &source_map::dummy_spanned(ast::VisibilityKind::Inherited));
+        s.end(); // Close the head box
+        s.end(); // Close the outer box
     })
 }
 
 pub fn block_to_string(blk: &ast::Block) -> String {
     to_string(|s| {
         // containing cbox, will be closed by print-block at }
-        s.cbox(INDENT_UNIT)?;
+        s.cbox(INDENT_UNIT);
         // head-ibox, will be closed by print-block after {
-        s.ibox(0)?;
+        s.ibox(0);
         s.print_block(blk)
     })
 }
@@ -424,14 +424,14 @@ pub trait PrintState<'a> {
     fn comments(&mut self) -> &mut Option<Vec<comments::Comment>>;
     fn cur_cmnt(&mut self) -> &mut usize;
 
-    fn word_space<S: Into<Cow<'static, str>>>(&mut self, w: S) -> io::Result<()> {
-        self.writer().word(w)?;
+    fn word_space<S: Into<Cow<'static, str>>>(&mut self, w: S) {
+        self.writer().word(w);
         self.writer().space()
     }
 
-    fn popen(&mut self) -> io::Result<()> { self.writer().word("(") }
+    fn popen(&mut self) { self.writer().word("(") }
 
-    fn pclose(&mut self) -> io::Result<()> { self.writer().word(")") }
+    fn pclose(&mut self) { self.writer().word(")") }
 
     fn is_begin(&mut self) -> bool {
         match self.writer().last_token() {
@@ -452,89 +452,86 @@ pub trait PrintState<'a> {
         self.writer().last_token().is_eof() || self.writer().last_token().is_hardbreak_tok()
     }
 
-    fn hardbreak_if_not_bol(&mut self) -> io::Result<()> {
+    fn hardbreak_if_not_bol(&mut self) {
         if !self.is_bol() {
-            self.writer().hardbreak()?
+            self.writer().hardbreak()
         }
-        Ok(())
     }
 
     // "raw box"
-    fn rbox(&mut self, u: usize, b: pp::Breaks) -> io::Result<()> {
+    fn rbox(&mut self, u: usize, b: pp::Breaks) {
         self.boxes().push(b);
         self.writer().rbox(u, b)
     }
 
-    fn ibox(&mut self, u: usize) -> io::Result<()> {
+    fn ibox(&mut self, u: usize) {
         self.boxes().push(pp::Breaks::Inconsistent);
-        self.writer().ibox(u)
+        self.writer().ibox(u);
     }
 
-    fn end(&mut self) -> io::Result<()> {
+    fn end(&mut self) {
         self.boxes().pop().unwrap();
         self.writer().end()
     }
 
-    fn commasep<T, F>(&mut self, b: Breaks, elts: &[T], mut op: F) -> io::Result<()>
-        where F: FnMut(&mut Self, &T) -> io::Result<()>,
+    fn commasep<T, F>(&mut self, b: Breaks, elts: &[T], mut op: F)
+        where F: FnMut(&mut Self, &T),
     {
-        self.rbox(0, b)?;
+        self.rbox(0, b);
         let mut first = true;
         for elt in elts {
-            if first { first = false; } else { self.word_space(",")?; }
-            op(self, elt)?;
+            if first { first = false; } else { self.word_space(","); }
+            op(self, elt);
         }
-        self.end()
+        self.end();
     }
 
-    fn maybe_print_comment(&mut self, pos: BytePos) -> io::Result<()> {
+    fn maybe_print_comment(&mut self, pos: BytePos) {
         while let Some(ref cmnt) = self.next_comment() {
             if cmnt.pos < pos {
-                self.print_comment(cmnt)?;
+                self.print_comment(cmnt);
             } else {
                 break
             }
         }
-        Ok(())
     }
 
     fn print_comment(&mut self,
-                     cmnt: &comments::Comment) -> io::Result<()> {
-        let r = match cmnt.style {
+                     cmnt: &comments::Comment) {
+        match cmnt.style {
             comments::Mixed => {
                 assert_eq!(cmnt.lines.len(), 1);
-                self.writer().zerobreak()?;
-                self.writer().word(cmnt.lines[0].clone())?;
+                self.writer().zerobreak();
+                self.writer().word(cmnt.lines[0].clone());
                 self.writer().zerobreak()
             }
             comments::Isolated => {
-                self.hardbreak_if_not_bol()?;
+                self.hardbreak_if_not_bol();
                 for line in &cmnt.lines {
                     // Don't print empty lines because they will end up as trailing
                     // whitespace
                     if !line.is_empty() {
-                        self.writer().word(line.clone())?;
+                        self.writer().word(line.clone());
                     }
-                    self.writer().hardbreak()?;
+                    self.writer().hardbreak();
                 }
-                Ok(())
             }
             comments::Trailing => {
                 if !self.is_bol() {
-                    self.writer().word(" ")?;
+                    self.writer().word(" ");
                 }
                 if cmnt.lines.len() == 1 {
-                    self.writer().word(cmnt.lines[0].clone())?;
+                    self.writer().word(cmnt.lines[0].clone());
                     self.writer().hardbreak()
                 } else {
-                    self.ibox(0)?;
+                    self.ibox(0);
                     for line in &cmnt.lines {
                         if !line.is_empty() {
-                            self.writer().word(line.clone())?;
+                            self.writer().word(line.clone());
                         }
-                        self.writer().hardbreak()?;
+                        self.writer().hardbreak();
                     }
-                    self.end()
+                    self.end();
                 }
             }
             comments::BlankLine => {
@@ -544,18 +541,12 @@ pub trait PrintState<'a> {
                     _ => false
                 };
                 if is_semi || self.is_begin() || self.is_end() {
-                    self.writer().hardbreak()?;
+                    self.writer().hardbreak();
                 }
-                self.writer().hardbreak()
-            }
-        };
-        match r {
-            Ok(()) => {
-                *self.cur_cmnt() = *self.cur_cmnt() + 1;
-                Ok(())
+                self.writer().hardbreak();
             }
-            Err(e) => Err(e),
         }
+        *self.cur_cmnt() = *self.cur_cmnt() + 1;
     }
 
     fn next_comment(&mut self) -> Option<comments::Comment> {
@@ -572,13 +563,13 @@ pub trait PrintState<'a> {
         }
     }
 
-    fn print_literal(&mut self, lit: &ast::Lit) -> io::Result<()> {
-        self.maybe_print_comment(lit.span.lo())?;
+    fn print_literal(&mut self, lit: &ast::Lit) {
+        self.maybe_print_comment(lit.span.lo());
         self.writer().word(literal_to_string(lit.token))
     }
 
     fn print_string(&mut self, st: &str,
-                    style: ast::StrStyle) -> io::Result<()> {
+                    style: ast::StrStyle) {
         let st = match style {
             ast::StrStyle::Cooked => {
                 (format!("\"{}\"", st.escape_debug()))
@@ -593,28 +584,28 @@ pub trait PrintState<'a> {
     }
 
     fn print_inner_attributes(&mut self,
-                              attrs: &[ast::Attribute]) -> io::Result<()> {
+                              attrs: &[ast::Attribute]) {
         self.print_either_attributes(attrs, ast::AttrStyle::Inner, false, true)
     }
 
     fn print_inner_attributes_no_trailing_hardbreak(&mut self,
                                                    attrs: &[ast::Attribute])
-                                                   -> io::Result<()> {
+                                                   {
         self.print_either_attributes(attrs, ast::AttrStyle::Inner, false, false)
     }
 
     fn print_outer_attributes(&mut self,
-                              attrs: &[ast::Attribute]) -> io::Result<()> {
+                              attrs: &[ast::Attribute]) {
         self.print_either_attributes(attrs, ast::AttrStyle::Outer, false, true)
     }
 
     fn print_inner_attributes_inline(&mut self,
-                                     attrs: &[ast::Attribute]) -> io::Result<()> {
+                                     attrs: &[ast::Attribute]) {
         self.print_either_attributes(attrs, ast::AttrStyle::Inner, true, true)
     }
 
     fn print_outer_attributes_inline(&mut self,
-                                     attrs: &[ast::Attribute]) -> io::Result<()> {
+                                     attrs: &[ast::Attribute]) {
         self.print_either_attributes(attrs, ast::AttrStyle::Outer, true, true)
     }
 
@@ -622,69 +613,67 @@ pub trait PrintState<'a> {
                               attrs: &[ast::Attribute],
                               kind: ast::AttrStyle,
                               is_inline: bool,
-                              trailing_hardbreak: bool) -> io::Result<()> {
+                              trailing_hardbreak: bool) {
         let mut count = 0;
         for attr in attrs {
             if attr.style == kind {
-                self.print_attribute_inline(attr, is_inline)?;
+                self.print_attribute_inline(attr, is_inline);
                 if is_inline {
-                    self.nbsp()?;
+                    self.nbsp();
                 }
                 count += 1;
             }
         }
         if count > 0 && trailing_hardbreak && !is_inline {
-            self.hardbreak_if_not_bol()?;
+            self.hardbreak_if_not_bol();
         }
-        Ok(())
     }
 
-    fn print_attribute_path(&mut self, path: &ast::Path) -> io::Result<()> {
+    fn print_attribute_path(&mut self, path: &ast::Path) {
         for (i, segment) in path.segments.iter().enumerate() {
             if i > 0 {
-                self.writer().word("::")?
+                self.writer().word("::");
             }
             if segment.ident.name != kw::PathRoot {
                 if segment.ident.name == kw::DollarCrate {
-                    self.print_dollar_crate(segment.ident)?;
+                    self.print_dollar_crate(segment.ident);
                 } else {
-                    self.writer().word(segment.ident.as_str().to_string())?;
+                    self.writer().word(segment.ident.as_str().to_string());
                 }
             }
         }
-        Ok(())
     }
 
-    fn print_attribute(&mut self, attr: &ast::Attribute) -> io::Result<()> {
+    fn print_attribute(&mut self, attr: &ast::Attribute) {
         self.print_attribute_inline(attr, false)
     }
 
     fn print_attribute_inline(&mut self, attr: &ast::Attribute,
-                              is_inline: bool) -> io::Result<()> {
+                              is_inline: bool) {
         if !is_inline {
-            self.hardbreak_if_not_bol()?;
+            self.hardbreak_if_not_bol();
         }
-        self.maybe_print_comment(attr.span.lo())?;
+        self.maybe_print_comment(attr.span.lo());
         if attr.is_sugared_doc {
-            self.writer().word(attr.value_str().unwrap().as_str().to_string())?;
+            self.writer().word(attr.value_str().unwrap().as_str().to_string());
             self.writer().hardbreak()
         } else {
             match attr.style {
-                ast::AttrStyle::Inner => self.writer().word("#![")?,
-                ast::AttrStyle::Outer => self.writer().word("#[")?,
+                ast::AttrStyle::Inner => self.writer().word("#!["),
+                ast::AttrStyle::Outer => self.writer().word("#["),
             }
             if let Some(mi) = attr.meta() {
-                self.print_meta_item(&mi)?
+                self.print_meta_item(&mi);
             } else {
-                self.print_attribute_path(&attr.path)?;
-                self.writer().space()?;
-                self.print_tts(attr.tokens.clone())?;
+                self.print_attribute_path(&attr.path);
+                self.writer().space();
+                self.print_tts(attr.tokens.clone());
             }
-            self.writer().word("]")
+            self.writer().word("]");
         }
     }
 
-    fn print_meta_list_item(&mut self, item: &ast::NestedMetaItem) -> io::Result<()> {
+    fn print_meta_list_item(&mut self, item: &ast::NestedMetaItem) {
         match item {
             ast::NestedMetaItem::MetaItem(ref mi) => {
                 self.print_meta_item(mi)
@@ -695,26 +684,26 @@ pub trait PrintState<'a> {
         }
     }
 
-    fn print_meta_item(&mut self, item: &ast::MetaItem) -> io::Result<()> {
-        self.ibox(INDENT_UNIT)?;
+    fn print_meta_item(&mut self, item: &ast::MetaItem) {
+        self.ibox(INDENT_UNIT);
         match item.node {
-            ast::MetaItemKind::Word => self.print_attribute_path(&item.path)?,
+            ast::MetaItemKind::Word => self.print_attribute_path(&item.path),
             ast::MetaItemKind::NameValue(ref value) => {
-                self.print_attribute_path(&item.path)?;
-                self.writer().space()?;
-                self.word_space("=")?;
-                self.print_literal(value)?;
+                self.print_attribute_path(&item.path);
+                self.writer().space();
+                self.word_space("=");
+                self.print_literal(value);
             }
             ast::MetaItemKind::List(ref items) => {
-                self.print_attribute_path(&item.path)?;
-                self.popen()?;
+                self.print_attribute_path(&item.path);
+                self.popen();
                 self.commasep(Consistent,
                               &items[..],
-                              |s, i| s.print_meta_list_item(i))?;
-                self.pclose()?;
+                              |s, i| s.print_meta_list_item(i));
+                self.pclose();
             }
         }
-        self.end()
+        self.end();
     }
 
     /// This doesn't deserve to be called "pretty" printing, but it should be
@@ -724,44 +713,43 @@ pub trait PrintState<'a> {
     /// appropriate macro, transcribe back into the grammar we just parsed from,
     /// and then pretty-print the resulting AST nodes (so, e.g., we print
     /// expression arguments as expressions). It can be done! I think.
-    fn print_tt(&mut self, tt: tokenstream::TokenTree) -> io::Result<()> {
+    fn print_tt(&mut self, tt: tokenstream::TokenTree) {
         match tt {
             TokenTree::Token(ref token) => {
-                self.writer().word(token_to_string(&token))?;
+                self.writer().word(token_to_string(&token));
                 match token.kind {
                     token::DocComment(..) => {
                         self.writer().hardbreak()
                     }
-                    _ => Ok(())
+                    _ => {}
                 }
             }
             TokenTree::Delimited(_, delim, tts) => {
-                self.writer().word(token_kind_to_string(&token::OpenDelim(delim)))?;
-                self.writer().space()?;
-                self.print_tts(tts)?;
-                self.writer().space()?;
+                self.writer().word(token_kind_to_string(&token::OpenDelim(delim)));
+                self.writer().space();
+                self.print_tts(tts);
+                self.writer().space();
                 self.writer().word(token_kind_to_string(&token::CloseDelim(delim)))
             },
         }
     }
 
-    fn print_tts(&mut self, tts: tokenstream::TokenStream) -> io::Result<()> {
-        self.ibox(0)?;
+    fn print_tts(&mut self, tts: tokenstream::TokenStream) {
+        self.ibox(0);
         for (i, tt) in tts.into_trees().enumerate() {
             if i != 0 {
-                self.writer().space()?;
+                self.writer().space();
             }
-            self.print_tt(tt)?;
+            self.print_tt(tt);
         }
-        self.end()
+        self.end();
     }
 
-    fn space_if_not_bol(&mut self) -> io::Result<()> {
-        if !self.is_bol() { self.writer().space()?; }
-        Ok(())
+    fn space_if_not_bol(&mut self) {
+        if !self.is_bol() { self.writer().space(); }
     }
 
-    fn nbsp(&mut self) -> io::Result<()> { self.writer().word(" ") }
+    fn nbsp(&mut self) { self.writer().word(" ") }
 
     // AST pretty-printer is used as a fallback for turning AST structures into token streams for
     // proc macros. Additionally, proc macros may stringify their input and expect it survive the
@@ -770,10 +758,10 @@ pub trait PrintState<'a> {
     // its hygiene data, most importantly name of the crate it refers to.
     // As a result we print `$crate` as `crate` if it refers to the local crate
     // and as `::other_crate_name` if it refers to some other crate.
-    fn print_dollar_crate(&mut self, ident: ast::Ident) -> io::Result<()> {
+    fn print_dollar_crate(&mut self, ident: ast::Ident) {
         let name = ident.span.ctxt().dollar_crate_name();
         if !ast::Ident::with_empty_ctxt(name).is_path_segment_keyword() {
-            self.writer().word("::")?;
+            self.writer().word("::");
         }
         self.writer().word(name.as_str().to_string())
     }
@@ -798,54 +786,52 @@ impl<'a> PrintState<'a> for State<'a> {
 }
 
 impl<'a> State<'a> {
-    pub fn cbox(&mut self, u: usize) -> io::Result<()> {
+    pub fn cbox(&mut self, u: usize) {
         self.boxes.push(pp::Breaks::Consistent);
-        self.s.cbox(u)
+        self.s.cbox(u);
     }
 
-    crate fn word_nbsp<S: Into<Cow<'static, str>>>(&mut self, w: S) -> io::Result<()> {
-        self.s.word(w)?;
+    crate fn word_nbsp<S: Into<Cow<'static, str>>>(&mut self, w: S) {
+        self.s.word(w);
         self.nbsp()
     }
 
-    crate fn head<S: Into<Cow<'static, str>>>(&mut self, w: S) -> io::Result<()> {
+    crate fn head<S: Into<Cow<'static, str>>>(&mut self, w: S) {
         let w = w.into();
         // outer-box is consistent
-        self.cbox(INDENT_UNIT)?;
+        self.cbox(INDENT_UNIT);
         // head-box is inconsistent
-        self.ibox(w.len() + 1)?;
+        self.ibox(w.len() + 1);
         // keyword that starts the head
         if !w.is_empty() {
-            self.word_nbsp(w)?;
+            self.word_nbsp(w);
         }
-        Ok(())
     }
 
-    crate fn bopen(&mut self) -> io::Result<()> {
-        self.s.word("{")?;
-        self.end() // close the head-box
+    crate fn bopen(&mut self) {
+        self.s.word("{");
+        self.end(); // close the head-box
     }
 
     crate fn bclose_(&mut self, span: syntax_pos::Span,
-                   indented: usize) -> io::Result<()> {
+                   indented: usize) {
         self.bclose_maybe_open(span, indented, true)
     }
     crate fn bclose_maybe_open(&mut self, span: syntax_pos::Span,
-                             indented: usize, close_box: bool) -> io::Result<()> {
-        self.maybe_print_comment(span.hi())?;
-        self.break_offset_if_not_bol(1, -(indented as isize))?;
-        self.s.word("}")?;
+                             indented: usize, close_box: bool) {
+        self.maybe_print_comment(span.hi());
+        self.break_offset_if_not_bol(1, -(indented as isize));
+        self.s.word("}");
         if close_box {
-            self.end()?; // close the outer-box
+            self.end(); // close the outer-box
         }
-        Ok(())
     }
-    crate fn bclose(&mut self, span: syntax_pos::Span) -> io::Result<()> {
+    crate fn bclose(&mut self, span: syntax_pos::Span) {
         self.bclose_(span, INDENT_UNIT)
     }
 
     crate fn break_offset_if_not_bol(&mut self, n: usize,
-                                   off: isize) -> io::Result<()> {
+                                   off: isize) {
         if !self.is_bol() {
             self.s.break_offset(n, off)
         } else {
@@ -855,17 +841,16 @@ impl<'a> State<'a> {
                 // break into the previous hardbreak.
                 self.s.replace_last_token(pp::Printer::hardbreak_tok_offset(off));
             }
-            Ok(())
         }
     }
 
     // Synthesizes a comment that was not textually present in the original source
     // file.
-    pub fn synth_comment(&mut self, text: String) -> io::Result<()> {
-        self.s.word("/*")?;
-        self.s.space()?;
-        self.s.word(text)?;
-        self.s.space()?;
+    pub fn synth_comment(&mut self, text: String) {
+        self.s.word("/*");
+        self.s.space();
+        self.s.word(text);
+        self.s.space();
         self.s.word("*/")
     }
 
@@ -875,59 +860,56 @@ impl<'a> State<'a> {
                                   b: Breaks,
                                   elts: &[T],
                                   mut op: F,
-                                  mut get_span: G) -> io::Result<()> where
-        F: FnMut(&mut State<'_>, &T) -> io::Result<()>,
+                                  mut get_span: G) where
+        F: FnMut(&mut State<'_>, &T),
         G: FnMut(&T) -> syntax_pos::Span,
     {
-        self.rbox(0, b)?;
+        self.rbox(0, b);
         let len = elts.len();
         let mut i = 0;
         for elt in elts {
-            self.maybe_print_comment(get_span(elt).hi())?;
-            op(self, elt)?;
+            self.maybe_print_comment(get_span(elt).hi());
+            op(self, elt);
             i += 1;
             if i < len {
-                self.s.word(",")?;
+                self.s.word(",");
                 self.maybe_print_trailing_comment(get_span(elt),
-                                                  Some(get_span(&elts[i]).hi()))?;
-                self.space_if_not_bol()?;
+                                                  Some(get_span(&elts[i]).hi()));
+                self.space_if_not_bol();
             }
         }
-        self.end()
+        self.end();
     }
 
     crate fn commasep_exprs(&mut self, b: Breaks,
-                          exprs: &[P<ast::Expr>]) -> io::Result<()> {
+                          exprs: &[P<ast::Expr>]) {
         self.commasep_cmnt(b, exprs, |s, e| s.print_expr(e), |e| e.span)
     }
 
     crate fn print_mod(&mut self, _mod: &ast::Mod,
-                     attrs: &[ast::Attribute]) -> io::Result<()> {
-        self.print_inner_attributes(attrs)?;
+                     attrs: &[ast::Attribute]) {
+        self.print_inner_attributes(attrs);
         for item in &_mod.items {
-            self.print_item(item)?;
+            self.print_item(item);
         }
-        Ok(())
     }
 
     crate fn print_foreign_mod(&mut self, nmod: &ast::ForeignMod,
-                             attrs: &[ast::Attribute]) -> io::Result<()> {
-        self.print_inner_attributes(attrs)?;
+                             attrs: &[ast::Attribute]) {
+        self.print_inner_attributes(attrs);
         for item in &nmod.items {
-            self.print_foreign_item(item)?;
+            self.print_foreign_item(item);
         }
-        Ok(())
     }
 
-    crate fn print_opt_lifetime(&mut self, lifetime: &Option<ast::Lifetime>) -> io::Result<()> {
+    crate fn print_opt_lifetime(&mut self, lifetime: &Option<ast::Lifetime>) {
         if let Some(lt) = *lifetime {
-            self.print_lifetime(lt)?;
-            self.nbsp()?;
+            self.print_lifetime(lt);
+            self.nbsp();
         }
-        Ok(())
     }
 
-    crate fn print_generic_arg(&mut self, generic_arg: &GenericArg) -> io::Result<()> {
+    crate fn print_generic_arg(&mut self, generic_arg: &GenericArg) {
         match generic_arg {
             GenericArg::Lifetime(lt) => self.print_lifetime(*lt),
             GenericArg::Type(ty) => self.print_type(ty),
@@ -935,136 +917,136 @@ impl<'a> State<'a> {
         }
     }
 
-    crate fn print_type(&mut self, ty: &ast::Ty) -> io::Result<()> {
-        self.maybe_print_comment(ty.span.lo())?;
-        self.ibox(0)?;
+    crate fn print_type(&mut self, ty: &ast::Ty) {
+        self.maybe_print_comment(ty.span.lo());
+        self.ibox(0);
         match ty.node {
             ast::TyKind::Slice(ref ty) => {
-                self.s.word("[")?;
-                self.print_type(ty)?;
-                self.s.word("]")?;
+                self.s.word("[");
+                self.print_type(ty);
+                self.s.word("]");
             }
             ast::TyKind::Ptr(ref mt) => {
-                self.s.word("*")?;
+                self.s.word("*");
                 match mt.mutbl {
-                    ast::Mutability::Mutable => self.word_nbsp("mut")?,
-                    ast::Mutability::Immutable => self.word_nbsp("const")?,
+                    ast::Mutability::Mutable => self.word_nbsp("mut"),
+                    ast::Mutability::Immutable => self.word_nbsp("const"),
                 }
-                self.print_type(&mt.ty)?;
+                self.print_type(&mt.ty);
             }
             ast::TyKind::Rptr(ref lifetime, ref mt) => {
-                self.s.word("&")?;
-                self.print_opt_lifetime(lifetime)?;
-                self.print_mt(mt)?;
+                self.s.word("&");
+                self.print_opt_lifetime(lifetime);
+                self.print_mt(mt);
             }
             ast::TyKind::Never => {
-                self.s.word("!")?;
+                self.s.word("!");
             },
             ast::TyKind::Tup(ref elts) => {
-                self.popen()?;
+                self.popen();
                 self.commasep(Inconsistent, &elts[..],
-                              |s, ty| s.print_type(ty))?;
+                              |s, ty| s.print_type(ty));
                 if elts.len() == 1 {
-                    self.s.word(",")?;
+                    self.s.word(",");
                 }
-                self.pclose()?;
+                self.pclose();
             }
             ast::TyKind::Paren(ref typ) => {
-                self.popen()?;
-                self.print_type(typ)?;
-                self.pclose()?;
+                self.popen();
+                self.print_type(typ);
+                self.pclose();
             }
             ast::TyKind::BareFn(ref f) => {
                 self.print_ty_fn(f.abi,
                                  f.unsafety,
                                  &f.decl,
                                  None,
-                                 &f.generic_params)?;
+                                 &f.generic_params);
             }
             ast::TyKind::Path(None, ref path) => {
-                self.print_path(path, false, 0)?;
+                self.print_path(path, false, 0);
             }
             ast::TyKind::Path(Some(ref qself), ref path) => {
-                self.print_qpath(path, qself, false)?
+                self.print_qpath(path, qself, false)
             }
             ast::TyKind::TraitObject(ref bounds, syntax) => {
                 let prefix = if syntax == ast::TraitObjectSyntax::Dyn { "dyn" } else { "" };
-                self.print_type_bounds(prefix, &bounds[..])?;
+                self.print_type_bounds(prefix, &bounds[..]);
             }
             ast::TyKind::ImplTrait(_, ref bounds) => {
-                self.print_type_bounds("impl", &bounds[..])?;
+                self.print_type_bounds("impl", &bounds[..]);
             }
             ast::TyKind::Array(ref ty, ref length) => {
-                self.s.word("[")?;
-                self.print_type(ty)?;
-                self.s.word("; ")?;
-                self.print_expr(&length.value)?;
-                self.s.word("]")?;
+                self.s.word("[");
+                self.print_type(ty);
+                self.s.word("; ");
+                self.print_expr(&length.value);
+                self.s.word("]");
             }
             ast::TyKind::Typeof(ref e) => {
-                self.s.word("typeof(")?;
-                self.print_expr(&e.value)?;
-                self.s.word(")")?;
+                self.s.word("typeof(");
+                self.print_expr(&e.value);
+                self.s.word(")");
             }
             ast::TyKind::Infer => {
-                self.s.word("_")?;
+                self.s.word("_");
             }
             ast::TyKind::Err => {
-                self.popen()?;
-                self.s.word("/*ERROR*/")?;
-                self.pclose()?;
+                self.popen();
+                self.s.word("/*ERROR*/");
+                self.pclose();
             }
             ast::TyKind::ImplicitSelf => {
-                self.s.word("Self")?;
+                self.s.word("Self");
             }
             ast::TyKind::Mac(ref m) => {
-                self.print_mac(m)?;
+                self.print_mac(m);
             }
             ast::TyKind::CVarArgs => {
-                self.s.word("...")?;
+                self.s.word("...");
             }
         }
-        self.end()
+        self.end();
     }
 
     crate fn print_foreign_item(&mut self,
-                              item: &ast::ForeignItem) -> io::Result<()> {
-        self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(item.span.lo())?;
-        self.print_outer_attributes(&item.attrs)?;
+                              item: &ast::ForeignItem) {
+        self.hardbreak_if_not_bol();
+        self.maybe_print_comment(item.span.lo());
+        self.print_outer_attributes(&item.attrs);
         match item.node {
             ast::ForeignItemKind::Fn(ref decl, ref generics) => {
-                self.head("")?;
+                self.head("");
                 self.print_fn(decl, ast::FnHeader::default(),
                               Some(item.ident),
-                              generics, &item.vis)?;
-                self.end()?; // end head-ibox
-                self.s.word(";")?;
-                self.end() // end the outer fn box
+                              generics, &item.vis);
+                self.end(); // end head-ibox
+                self.s.word(";");
+                self.end(); // end the outer fn box
             }
             ast::ForeignItemKind::Static(ref t, m) => {
-                self.head(visibility_qualified(&item.vis, "static"))?;
+                self.head(visibility_qualified(&item.vis, "static"));
                 if m == ast::Mutability::Mutable {
-                    self.word_space("mut")?;
+                    self.word_space("mut");
                 }
-                self.print_ident(item.ident)?;
-                self.word_space(":")?;
-                self.print_type(t)?;
-                self.s.word(";")?;
-                self.end()?; // end the head-ibox
-                self.end() // end the outer cbox
+                self.print_ident(item.ident);
+                self.word_space(":");
+                self.print_type(t);
+                self.s.word(";");
+                self.end(); // end the head-ibox
+                self.end(); // end the outer cbox
             }
             ast::ForeignItemKind::Ty => {
-                self.head(visibility_qualified(&item.vis, "type"))?;
-                self.print_ident(item.ident)?;
-                self.s.word(";")?;
-                self.end()?; // end the head-ibox
-                self.end() // end the outer cbox
+                self.head(visibility_qualified(&item.vis, "type"));
+                self.print_ident(item.ident);
+                self.s.word(";");
+                self.end(); // end the head-ibox
+                self.end(); // end the outer cbox
             }
             ast::ForeignItemKind::Macro(ref m) => {
-                self.print_mac(m)?;
+                self.print_mac(m);
                 match m.node.delim {
-                    MacDelimiter::Brace => Ok(()),
+                    MacDelimiter::Brace => {},
                     _ => self.s.word(";")
                 }
             }
@@ -1076,17 +1058,16 @@ impl<'a> State<'a> {
                               ty: &ast::Ty,
                               default: Option<&ast::Expr>,
                               vis: &ast::Visibility)
-                              -> io::Result<()>
     {
-        self.s.word(visibility_qualified(vis, ""))?;
-        self.word_space("const")?;
-        self.print_ident(ident)?;
-        self.word_space(":")?;
-        self.print_type(ty)?;
+        self.s.word(visibility_qualified(vis, ""));
+        self.word_space("const");
+        self.print_ident(ident);
+        self.word_space(":");
+        self.print_type(ty);
         if let Some(expr) = default {
-            self.s.space()?;
-            self.word_space("=")?;
-            self.print_expr(expr)?;
+            self.s.space();
+            self.word_space("=");
+            self.print_expr(expr);
         }
         self.s.word(";")
     }
@@ -1095,140 +1076,140 @@ impl<'a> State<'a> {
                              ident: ast::Ident,
                              bounds: Option<&ast::GenericBounds>,
                              ty: Option<&ast::Ty>)
-                             -> io::Result<()> {
-        self.word_space("type")?;
-        self.print_ident(ident)?;
+                             {
+        self.word_space("type");
+        self.print_ident(ident);
         if let Some(bounds) = bounds {
-            self.print_type_bounds(":", bounds)?;
+            self.print_type_bounds(":", bounds);
         }
         if let Some(ty) = ty {
-            self.s.space()?;
-            self.word_space("=")?;
-            self.print_type(ty)?;
+            self.s.space();
+            self.word_space("=");
+            self.print_type(ty);
         }
         self.s.word(";")
     }
 
     /// Pretty-print an item
-    crate fn print_item(&mut self, item: &ast::Item) -> io::Result<()> {
-        self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(item.span.lo())?;
-        self.print_outer_attributes(&item.attrs)?;
-        self.ann.pre(self, AnnNode::Item(item))?;
+    crate fn print_item(&mut self, item: &ast::Item) {
+        self.hardbreak_if_not_bol();
+        self.maybe_print_comment(item.span.lo());
+        self.print_outer_attributes(&item.attrs);
+        self.ann.pre(self, AnnNode::Item(item));
         match item.node {
             ast::ItemKind::ExternCrate(orig_name) => {
-                self.head(visibility_qualified(&item.vis, "extern crate"))?;
+                self.head(visibility_qualified(&item.vis, "extern crate"));
                 if let Some(orig_name) = orig_name {
-                    self.print_name(orig_name)?;
-                    self.s.space()?;
-                    self.s.word("as")?;
-                    self.s.space()?;
+                    self.print_name(orig_name);
+                    self.s.space();
+                    self.s.word("as");
+                    self.s.space();
                 }
-                self.print_ident(item.ident)?;
-                self.s.word(";")?;
-                self.end()?; // end inner head-block
-                self.end()?; // end outer head-block
+                self.print_ident(item.ident);
+                self.s.word(";");
+                self.end(); // end inner head-block
+                self.end(); // end outer head-block
             }
             ast::ItemKind::Use(ref tree) => {
-                self.head(visibility_qualified(&item.vis, "use"))?;
-                self.print_use_tree(tree)?;
-                self.s.word(";")?;
-                self.end()?; // end inner head-block
-                self.end()?; // end outer head-block
+                self.head(visibility_qualified(&item.vis, "use"));
+                self.print_use_tree(tree);
+                self.s.word(";");
+                self.end(); // end inner head-block
+                self.end(); // end outer head-block
             }
             ast::ItemKind::Static(ref ty, m, ref expr) => {
-                self.head(visibility_qualified(&item.vis, "static"))?;
+                self.head(visibility_qualified(&item.vis, "static"));
                 if m == ast::Mutability::Mutable {
-                    self.word_space("mut")?;
+                    self.word_space("mut");
                 }
-                self.print_ident(item.ident)?;
-                self.word_space(":")?;
-                self.print_type(ty)?;
-                self.s.space()?;
-                self.end()?; // end the head-ibox
+                self.print_ident(item.ident);
+                self.word_space(":");
+                self.print_type(ty);
+                self.s.space();
+                self.end(); // end the head-ibox
 
-                self.word_space("=")?;
-                self.print_expr(expr)?;
-                self.s.word(";")?;
-                self.end()?; // end the outer cbox
+                self.word_space("=");
+                self.print_expr(expr);
+                self.s.word(";");
+                self.end(); // end the outer cbox
             }
             ast::ItemKind::Const(ref ty, ref expr) => {
-                self.head(visibility_qualified(&item.vis, "const"))?;
-                self.print_ident(item.ident)?;
-                self.word_space(":")?;
-                self.print_type(ty)?;
-                self.s.space()?;
-                self.end()?; // end the head-ibox
-
-                self.word_space("=")?;
-                self.print_expr(expr)?;
-                self.s.word(";")?;
-                self.end()?; // end the outer cbox
+                self.head(visibility_qualified(&item.vis, "const"));
+                self.print_ident(item.ident);
+                self.word_space(":");
+                self.print_type(ty);
+                self.s.space();
+                self.end(); // end the head-ibox
+
+                self.word_space("=");
+                self.print_expr(expr);
+                self.s.word(";");
+                self.end(); // end the outer cbox
             }
             ast::ItemKind::Fn(ref decl, header, ref param_names, ref body) => {
-                self.head("")?;
+                self.head("");
                 self.print_fn(
                     decl,
                     header,
                     Some(item.ident),
                     param_names,
                     &item.vis
-                )?;
-                self.s.word(" ")?;
-                self.print_block_with_attrs(body, &item.attrs)?;
+                );
+                self.s.word(" ");
+                self.print_block_with_attrs(body, &item.attrs);
             }
             ast::ItemKind::Mod(ref _mod) => {
-                self.head(visibility_qualified(&item.vis, "mod"))?;
-                self.print_ident(item.ident)?;
+                self.head(visibility_qualified(&item.vis, "mod"));
+                self.print_ident(item.ident);
 
                 if _mod.inline || self.is_expanded {
-                    self.nbsp()?;
-                    self.bopen()?;
-                    self.print_mod(_mod, &item.attrs)?;
-                    self.bclose(item.span)?;
+                    self.nbsp();
+                    self.bopen();
+                    self.print_mod(_mod, &item.attrs);
+                    self.bclose(item.span);
                 } else {
-                    self.s.word(";")?;
-                    self.end()?; // end inner head-block
-                    self.end()?; // end outer head-block
+                    self.s.word(";");
+                    self.end(); // end inner head-block
+                    self.end(); // end outer head-block
                 }
 
             }
             ast::ItemKind::ForeignMod(ref nmod) => {
-                self.head("extern")?;
-                self.word_nbsp(nmod.abi.to_string())?;
-                self.bopen()?;
-                self.print_foreign_mod(nmod, &item.attrs)?;
-                self.bclose(item.span)?;
+                self.head("extern");
+                self.word_nbsp(nmod.abi.to_string());
+                self.bopen();
+                self.print_foreign_mod(nmod, &item.attrs);
+                self.bclose(item.span);
             }
             ast::ItemKind::GlobalAsm(ref ga) => {
-                self.head(visibility_qualified(&item.vis, "global_asm!"))?;
-                self.s.word(ga.asm.as_str().to_string())?;
-                self.end()?;
+                self.head(visibility_qualified(&item.vis, "global_asm!"));
+                self.s.word(ga.asm.as_str().to_string());
+                self.end();
             }
             ast::ItemKind::Ty(ref ty, ref generics) => {
-                self.head(visibility_qualified(&item.vis, "type"))?;
-                self.print_ident(item.ident)?;
-                self.print_generic_params(&generics.params)?;
-                self.end()?; // end the inner ibox
-
-                self.print_where_clause(&generics.where_clause)?;
-                self.s.space()?;
-                self.word_space("=")?;
-                self.print_type(ty)?;
-                self.s.word(";")?;
-                self.end()?; // end the outer ibox
+                self.head(visibility_qualified(&item.vis, "type"));
+                self.print_ident(item.ident);
+                self.print_generic_params(&generics.params);
+                self.end(); // end the inner ibox
+
+                self.print_where_clause(&generics.where_clause);
+                self.s.space();
+                self.word_space("=");
+                self.print_type(ty);
+                self.s.word(";");
+                self.end(); // end the outer ibox
             }
             ast::ItemKind::Existential(ref bounds, ref generics) => {
-                self.head(visibility_qualified(&item.vis, "existential type"))?;
-                self.print_ident(item.ident)?;
-                self.print_generic_params(&generics.params)?;
-                self.end()?; // end the inner ibox
+                self.head(visibility_qualified(&item.vis, "existential type"));
+                self.print_ident(item.ident);
+                self.print_generic_params(&generics.params);
+                self.end(); // end the inner ibox
 
-                self.print_where_clause(&generics.where_clause)?;
-                self.s.space()?;
-                self.print_type_bounds(":", bounds)?;
-                self.s.word(";")?;
-                self.end()?; // end the outer ibox
+                self.print_where_clause(&generics.where_clause);
+                self.s.space();
+                self.print_type_bounds(":", bounds);
+                self.s.word(";");
+                self.end(); // end the outer ibox
             }
             ast::ItemKind::Enum(ref enum_definition, ref params) => {
                 self.print_enum_def(
@@ -1237,15 +1218,15 @@ impl<'a> State<'a> {
                     item.ident,
                     item.span,
                     &item.vis
-                )?;
+                );
             }
             ast::ItemKind::Struct(ref struct_def, ref generics) => {
-                self.head(visibility_qualified(&item.vis, "struct"))?;
-                self.print_struct(struct_def, generics, item.ident, item.span, true)?;
+                self.head(visibility_qualified(&item.vis, "struct"));
+                self.print_struct(struct_def, generics, item.ident, item.span, true);
             }
             ast::ItemKind::Union(ref struct_def, ref generics) => {
-                self.head(visibility_qualified(&item.vis, "union"))?;
-                self.print_struct(struct_def, generics, item.ident, item.span, true)?;
+                self.head(visibility_qualified(&item.vis, "union"));
+                self.print_struct(struct_def, generics, item.ident, item.span, true);
             }
             ast::ItemKind::Impl(unsafety,
                           polarity,
@@ -1254,171 +1235,170 @@ impl<'a> State<'a> {
                           ref opt_trait,
                           ref ty,
                           ref impl_items) => {
-                self.head("")?;
-                self.print_visibility(&item.vis)?;
-                self.print_defaultness(defaultness)?;
-                self.print_unsafety(unsafety)?;
-                self.word_nbsp("impl")?;
+                self.head("");
+                self.print_visibility(&item.vis);
+                self.print_defaultness(defaultness);
+                self.print_unsafety(unsafety);
+                self.word_nbsp("impl");
 
                 if !generics.params.is_empty() {
-                    self.print_generic_params(&generics.params)?;
-                    self.s.space()?;
+                    self.print_generic_params(&generics.params);
+                    self.s.space();
                 }
 
                 if polarity == ast::ImplPolarity::Negative {
-                    self.s.word("!")?;
+                    self.s.word("!");
                 }
 
                 if let Some(ref t) = *opt_trait {
-                    self.print_trait_ref(t)?;
-                    self.s.space()?;
-                    self.word_space("for")?;
+                    self.print_trait_ref(t);
+                    self.s.space();
+                    self.word_space("for");
                 }
 
-                self.print_type(ty)?;
-                self.print_where_clause(&generics.where_clause)?;
+                self.print_type(ty);
+                self.print_where_clause(&generics.where_clause);
 
-                self.s.space()?;
-                self.bopen()?;
-                self.print_inner_attributes(&item.attrs)?;
+                self.s.space();
+                self.bopen();
+                self.print_inner_attributes(&item.attrs);
                 for impl_item in impl_items {
-                    self.print_impl_item(impl_item)?;
+                    self.print_impl_item(impl_item);
                 }
-                self.bclose(item.span)?;
+                self.bclose(item.span);
             }
             ast::ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref trait_items) => {
-                self.head("")?;
-                self.print_visibility(&item.vis)?;
-                self.print_unsafety(unsafety)?;
-                self.print_is_auto(is_auto)?;
-                self.word_nbsp("trait")?;
-                self.print_ident(item.ident)?;
-                self.print_generic_params(&generics.params)?;
+                self.head("");
+                self.print_visibility(&item.vis);
+                self.print_unsafety(unsafety);
+                self.print_is_auto(is_auto);
+                self.word_nbsp("trait");
+                self.print_ident(item.ident);
+                self.print_generic_params(&generics.params);
                 let mut real_bounds = Vec::with_capacity(bounds.len());
                 for b in bounds.iter() {
                     if let GenericBound::Trait(ref ptr, ast::TraitBoundModifier::Maybe) = *b {
-                        self.s.space()?;
-                        self.word_space("for ?")?;
-                        self.print_trait_ref(&ptr.trait_ref)?;
+                        self.s.space();
+                        self.word_space("for ?");
+                        self.print_trait_ref(&ptr.trait_ref);
                     } else {
                         real_bounds.push(b.clone());
                     }
                 }
-                self.print_type_bounds(":", &real_bounds[..])?;
-                self.print_where_clause(&generics.where_clause)?;
-                self.s.word(" ")?;
-                self.bopen()?;
+                self.print_type_bounds(":", &real_bounds[..]);
+                self.print_where_clause(&generics.where_clause);
+                self.s.word(" ");
+                self.bopen();
                 for trait_item in trait_items {
-                    self.print_trait_item(trait_item)?;
+                    self.print_trait_item(trait_item);
                 }
-                self.bclose(item.span)?;
+                self.bclose(item.span);
             }
             ast::ItemKind::TraitAlias(ref generics, ref bounds) => {
-                self.head("")?;
-                self.print_visibility(&item.vis)?;
-                self.word_nbsp("trait")?;
-                self.print_ident(item.ident)?;
-                self.print_generic_params(&generics.params)?;
+                self.head("");
+                self.print_visibility(&item.vis);
+                self.word_nbsp("trait");
+                self.print_ident(item.ident);
+                self.print_generic_params(&generics.params);
                 let mut real_bounds = Vec::with_capacity(bounds.len());
                 // FIXME(durka) this seems to be some quite outdated syntax
                 for b in bounds.iter() {
                     if let GenericBound::Trait(ref ptr, ast::TraitBoundModifier::Maybe) = *b {
-                        self.s.space()?;
-                        self.word_space("for ?")?;
-                        self.print_trait_ref(&ptr.trait_ref)?;
+                        self.s.space();
+                        self.word_space("for ?");
+                        self.print_trait_ref(&ptr.trait_ref);
                     } else {
                         real_bounds.push(b.clone());
                     }
                 }
-                self.nbsp()?;
-                self.print_type_bounds("=", &real_bounds[..])?;
-                self.print_where_clause(&generics.where_clause)?;
-                self.s.word(";")?;
+                self.nbsp();
+                self.print_type_bounds("=", &real_bounds[..]);
+                self.print_where_clause(&generics.where_clause);
+                self.s.word(";");
             }
             ast::ItemKind::Mac(ref mac) => {
                 if item.ident.name == kw::Invalid {
-                    self.print_mac(mac)?;
+                    self.print_mac(mac);
                     match mac.node.delim {
                         MacDelimiter::Brace => {}
-                        _ => self.s.word(";")?,
+                        _ => self.s.word(";"),
                     }
                 } else {
-                    self.print_path(&mac.node.path, false, 0)?;
-                    self.s.word("! ")?;
-                    self.print_ident(item.ident)?;
-                    self.cbox(INDENT_UNIT)?;
-                    self.popen()?;
-                    self.print_tts(mac.node.stream())?;
-                    self.pclose()?;
-                    self.s.word(";")?;
-                    self.end()?;
+                    self.print_path(&mac.node.path, false, 0);
+                    self.s.word("! ");
+                    self.print_ident(item.ident);
+                    self.cbox(INDENT_UNIT);
+                    self.popen();
+                    self.print_tts(mac.node.stream());
+                    self.pclose();
+                    self.s.word(";");
+                    self.end();
                 }
             }
             ast::ItemKind::MacroDef(ref tts) => {
-                self.s.word("macro_rules! ")?;
-                self.print_ident(item.ident)?;
-                self.cbox(INDENT_UNIT)?;
-                self.popen()?;
-                self.print_tts(tts.stream())?;
-                self.pclose()?;
-                self.s.word(";")?;
-                self.end()?;
+                self.s.word("macro_rules! ");
+                self.print_ident(item.ident);
+                self.cbox(INDENT_UNIT);
+                self.popen();
+                self.print_tts(tts.stream());
+                self.pclose();
+                self.s.word(";");
+                self.end();
             }
         }
         self.ann.post(self, AnnNode::Item(item))
     }
 
-    fn print_trait_ref(&mut self, t: &ast::TraitRef) -> io::Result<()> {
+    fn print_trait_ref(&mut self, t: &ast::TraitRef) {
         self.print_path(&t.path, false, 0)
     }
 
     fn print_formal_generic_params(
         &mut self,
         generic_params: &[ast::GenericParam]
-    ) -> io::Result<()> {
+    ) {
         if !generic_params.is_empty() {
-            self.s.word("for")?;
-            self.print_generic_params(generic_params)?;
-            self.nbsp()?;
+            self.s.word("for");
+            self.print_generic_params(generic_params);
+            self.nbsp();
         }
-        Ok(())
     }
 
-    fn print_poly_trait_ref(&mut self, t: &ast::PolyTraitRef) -> io::Result<()> {
-        self.print_formal_generic_params(&t.bound_generic_params)?;
+    fn print_poly_trait_ref(&mut self, t: &ast::PolyTraitRef) {
+        self.print_formal_generic_params(&t.bound_generic_params);
         self.print_trait_ref(&t.trait_ref)
     }
 
     crate fn print_enum_def(&mut self, enum_definition: &ast::EnumDef,
                           generics: &ast::Generics, ident: ast::Ident,
                           span: syntax_pos::Span,
-                          visibility: &ast::Visibility) -> io::Result<()> {
-        self.head(visibility_qualified(visibility, "enum"))?;
-        self.print_ident(ident)?;
-        self.print_generic_params(&generics.params)?;
-        self.print_where_clause(&generics.where_clause)?;
-        self.s.space()?;
+                          visibility: &ast::Visibility) {
+        self.head(visibility_qualified(visibility, "enum"));
+        self.print_ident(ident);
+        self.print_generic_params(&generics.params);
+        self.print_where_clause(&generics.where_clause);
+        self.s.space();
         self.print_variants(&enum_definition.variants, span)
     }
 
     crate fn print_variants(&mut self,
                           variants: &[ast::Variant],
-                          span: syntax_pos::Span) -> io::Result<()> {
-        self.bopen()?;
+                          span: syntax_pos::Span) {
+        self.bopen();
         for v in variants {
-            self.space_if_not_bol()?;
-            self.maybe_print_comment(v.span.lo())?;
-            self.print_outer_attributes(&v.node.attrs)?;
-            self.ibox(INDENT_UNIT)?;
-            self.print_variant(v)?;
-            self.s.word(",")?;
-            self.end()?;
-            self.maybe_print_trailing_comment(v.span, None)?;
+            self.space_if_not_bol();
+            self.maybe_print_comment(v.span.lo());
+            self.print_outer_attributes(&v.node.attrs);
+            self.ibox(INDENT_UNIT);
+            self.print_variant(v);
+            self.s.word(",");
+            self.end();
+            self.maybe_print_trailing_comment(v.span, None);
         }
         self.bclose(span)
     }
 
-    crate fn print_visibility(&mut self, vis: &ast::Visibility) -> io::Result<()> {
+    crate fn print_visibility(&mut self, vis: &ast::Visibility) {
         match vis.node {
             ast::VisibilityKind::Public => self.word_nbsp("pub"),
             ast::VisibilityKind::Crate(sugar) => match sugar {
@@ -1433,15 +1413,14 @@ impl<'a> State<'a> {
                     self.word_nbsp(format!("pub(in {})", path))
                 }
             }
-            ast::VisibilityKind::Inherited => Ok(())
+            ast::VisibilityKind::Inherited => {}
         }
     }
 
-    crate fn print_defaultness(&mut self, defaultness: ast::Defaultness) -> io::Result<()> {
+    crate fn print_defaultness(&mut self, defaultness: ast::Defaultness) {
         if let ast::Defaultness::Default = defaultness {
-            self.word_nbsp("default")?;
+            self.word_nbsp("default");
         }
-        Ok(())
     }
 
     crate fn print_struct(&mut self,
@@ -1449,46 +1428,46 @@ impl<'a> State<'a> {
                         generics: &ast::Generics,
                         ident: ast::Ident,
                         span: syntax_pos::Span,
-                        print_finalizer: bool) -> io::Result<()> {
-        self.print_ident(ident)?;
-        self.print_generic_params(&generics.params)?;
+                        print_finalizer: bool) {
+        self.print_ident(ident);
+        self.print_generic_params(&generics.params);
         match struct_def {
             ast::VariantData::Tuple(..) | ast::VariantData::Unit(..) => {
                 if let ast::VariantData::Tuple(..) = struct_def {
-                    self.popen()?;
+                    self.popen();
                     self.commasep(
                         Inconsistent, struct_def.fields(),
                         |s, field| {
-                            s.maybe_print_comment(field.span.lo())?;
-                            s.print_outer_attributes(&field.attrs)?;
-                            s.print_visibility(&field.vis)?;
+                            s.maybe_print_comment(field.span.lo());
+                            s.print_outer_attributes(&field.attrs);
+                            s.print_visibility(&field.vis);
                             s.print_type(&field.ty)
                         }
-                    )?;
-                    self.pclose()?;
+                    );
+                    self.pclose();
                 }
-                self.print_where_clause(&generics.where_clause)?;
+                self.print_where_clause(&generics.where_clause);
                 if print_finalizer {
-                    self.s.word(";")?;
+                    self.s.word(";");
                 }
-                self.end()?;
-                self.end() // close the outer-box
+                self.end();
+                self.end(); // close the outer-box
             }
             ast::VariantData::Struct(..) => {
-                self.print_where_clause(&generics.where_clause)?;
-                self.nbsp()?;
-                self.bopen()?;
-                self.hardbreak_if_not_bol()?;
+                self.print_where_clause(&generics.where_clause);
+                self.nbsp();
+                self.bopen();
+                self.hardbreak_if_not_bol();
 
                 for field in struct_def.fields() {
-                    self.hardbreak_if_not_bol()?;
-                    self.maybe_print_comment(field.span.lo())?;
-                    self.print_outer_attributes(&field.attrs)?;
-                    self.print_visibility(&field.vis)?;
-                    self.print_ident(field.ident.unwrap())?;
-                    self.word_nbsp(":")?;
-                    self.print_type(&field.ty)?;
-                    self.s.word(",")?;
+                    self.hardbreak_if_not_bol();
+                    self.maybe_print_comment(field.span.lo());
+                    self.print_outer_attributes(&field.attrs);
+                    self.print_visibility(&field.vis);
+                    self.print_ident(field.ident.unwrap());
+                    self.word_nbsp(":");
+                    self.print_type(&field.ty);
+                    self.s.word(",");
                 }
 
                 self.bclose(span)
@@ -1496,17 +1475,17 @@ impl<'a> State<'a> {
         }
     }
 
-    crate fn print_variant(&mut self, v: &ast::Variant) -> io::Result<()> {
-        self.head("")?;
+    crate fn print_variant(&mut self, v: &ast::Variant) {
+        self.head("");
         let generics = ast::Generics::default();
-        self.print_struct(&v.node.data, &generics, v.node.ident, v.span, false)?;
+        self.print_struct(&v.node.data, &generics, v.node.ident, v.span, false);
         match v.node.disr_expr {
             Some(ref d) => {
-                self.s.space()?;
-                self.word_space("=")?;
+                self.s.space();
+                self.word_space("=");
                 self.print_expr(&d.value)
             }
-            _ => Ok(())
+            _ => {}
         }
     }
 
@@ -1515,7 +1494,7 @@ impl<'a> State<'a> {
                             generics: &ast::Generics,
                             m: &ast::MethodSig,
                             vis: &ast::Visibility)
-                            -> io::Result<()> {
+                            {
         self.print_fn(&m.decl,
                       m.header,
                       Some(ident),
@@ -1524,11 +1503,11 @@ impl<'a> State<'a> {
     }
 
     crate fn print_trait_item(&mut self, ti: &ast::TraitItem)
-                            -> io::Result<()> {
-        self.ann.pre(self, AnnNode::SubItem(ti.id))?;
-        self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(ti.span.lo())?;
-        self.print_outer_attributes(&ti.attrs)?;
+                            {
+        self.ann.pre(self, AnnNode::SubItem(ti.id));
+        self.hardbreak_if_not_bol();
+        self.maybe_print_comment(ti.span.lo());
+        self.print_outer_attributes(&ti.attrs);
         match ti.node {
             ast::TraitItemKind::Const(ref ty, ref default) => {
                 self.print_associated_const(
@@ -1536,132 +1515,132 @@ impl<'a> State<'a> {
                     ty,
                     default.as_ref().map(|expr| &**expr),
                     &source_map::respan(ti.span.shrink_to_lo(), ast::VisibilityKind::Inherited),
-                )?;
+                );
             }
             ast::TraitItemKind::Method(ref sig, ref body) => {
                 if body.is_some() {
-                    self.head("")?;
+                    self.head("");
                 }
                 self.print_method_sig(
                     ti.ident,
                     &ti.generics,
                     sig,
                     &source_map::respan(ti.span.shrink_to_lo(), ast::VisibilityKind::Inherited),
-                )?;
+                );
                 if let Some(ref body) = *body {
-                    self.nbsp()?;
-                    self.print_block_with_attrs(body, &ti.attrs)?;
+                    self.nbsp();
+                    self.print_block_with_attrs(body, &ti.attrs);
                 } else {
-                    self.s.word(";")?;
+                    self.s.word(";");
                 }
             }
             ast::TraitItemKind::Type(ref bounds, ref default) => {
                 self.print_associated_type(ti.ident, Some(bounds),
-                                           default.as_ref().map(|ty| &**ty))?;
+                                           default.as_ref().map(|ty| &**ty));
             }
             ast::TraitItemKind::Macro(ref mac) => {
-                self.print_mac(mac)?;
+                self.print_mac(mac);
                 match mac.node.delim {
                     MacDelimiter::Brace => {}
-                    _ => self.s.word(";")?,
+                    _ => self.s.word(";"),
                 }
             }
         }
         self.ann.post(self, AnnNode::SubItem(ti.id))
     }
 
-    crate fn print_impl_item(&mut self, ii: &ast::ImplItem) -> io::Result<()> {
-        self.ann.pre(self, AnnNode::SubItem(ii.id))?;
-        self.hardbreak_if_not_bol()?;
-        self.maybe_print_comment(ii.span.lo())?;
-        self.print_outer_attributes(&ii.attrs)?;
-        self.print_defaultness(ii.defaultness)?;
+    crate fn print_impl_item(&mut self, ii: &ast::ImplItem) {
+        self.ann.pre(self, AnnNode::SubItem(ii.id));
+        self.hardbreak_if_not_bol();
+        self.maybe_print_comment(ii.span.lo());
+        self.print_outer_attributes(&ii.attrs);
+        self.print_defaultness(ii.defaultness);
         match ii.node {
             ast::ImplItemKind::Const(ref ty, ref expr) => {
-                self.print_associated_const(ii.ident, ty, Some(expr), &ii.vis)?;
+                self.print_associated_const(ii.ident, ty, Some(expr), &ii.vis);
             }
             ast::ImplItemKind::Method(ref sig, ref body) => {
-                self.head("")?;
-                self.print_method_sig(ii.ident, &ii.generics, sig, &ii.vis)?;
-                self.nbsp()?;
-                self.print_block_with_attrs(body, &ii.attrs)?;
+                self.head("");
+                self.print_method_sig(ii.ident, &ii.generics, sig, &ii.vis);
+                self.nbsp();
+                self.print_block_with_attrs(body, &ii.attrs);
             }
             ast::ImplItemKind::Type(ref ty) => {
-                self.print_associated_type(ii.ident, None, Some(ty))?;
+                self.print_associated_type(ii.ident, None, Some(ty));
             }
             ast::ImplItemKind::Existential(ref bounds) => {
-                self.word_space("existential")?;
-                self.print_associated_type(ii.ident, Some(bounds), None)?;
+                self.word_space("existential");
+                self.print_associated_type(ii.ident, Some(bounds), None);
             }
             ast::ImplItemKind::Macro(ref mac) => {
-                self.print_mac(mac)?;
+                self.print_mac(mac);
                 match mac.node.delim {
                     MacDelimiter::Brace => {}
-                    _ => self.s.word(";")?,
+                    _ => self.s.word(";"),
                 }
             }
         }
         self.ann.post(self, AnnNode::SubItem(ii.id))
     }
 
-    crate fn print_stmt(&mut self, st: &ast::Stmt) -> io::Result<()> {
-        self.maybe_print_comment(st.span.lo())?;
+    crate fn print_stmt(&mut self, st: &ast::Stmt) {
+        self.maybe_print_comment(st.span.lo());
         match st.node {
             ast::StmtKind::Local(ref loc) => {
-                self.print_outer_attributes(&loc.attrs)?;
-                self.space_if_not_bol()?;
-                self.ibox(INDENT_UNIT)?;
-                self.word_nbsp("let")?;
-
-                self.ibox(INDENT_UNIT)?;
-                self.print_local_decl(loc)?;
-                self.end()?;
+                self.print_outer_attributes(&loc.attrs);
+                self.space_if_not_bol();
+                self.ibox(INDENT_UNIT);
+                self.word_nbsp("let");
+
+                self.ibox(INDENT_UNIT);
+                self.print_local_decl(loc);
+                self.end();
                 if let Some(ref init) = loc.init {
-                    self.nbsp()?;
-                    self.word_space("=")?;
-                    self.print_expr(init)?;
+                    self.nbsp();
+                    self.word_space("=");
+                    self.print_expr(init);
                 }
-                self.s.word(";")?;
-                self.end()?;
+                self.s.word(";");
+                self.end();
             }
-            ast::StmtKind::Item(ref item) => self.print_item(item)?,
+            ast::StmtKind::Item(ref item) => self.print_item(item),
             ast::StmtKind::Expr(ref expr) => {
-                self.space_if_not_bol()?;
-                self.print_expr_outer_attr_style(expr, false)?;
+                self.space_if_not_bol();
+                self.print_expr_outer_attr_style(expr, false);
                 if parse::classify::expr_requires_semi_to_be_stmt(expr) {
-                    self.s.word(";")?;
+                    self.s.word(";");
                 }
             }
             ast::StmtKind::Semi(ref expr) => {
-                self.space_if_not_bol()?;
-                self.print_expr_outer_attr_style(expr, false)?;
-                self.s.word(";")?;
+                self.space_if_not_bol();
+                self.print_expr_outer_attr_style(expr, false);
+                self.s.word(";");
             }
             ast::StmtKind::Mac(ref mac) => {
                 let (ref mac, style, ref attrs) = **mac;
-                self.space_if_not_bol()?;
-                self.print_outer_attributes(attrs)?;
-                self.print_mac(mac)?;
+                self.space_if_not_bol();
+                self.print_outer_attributes(attrs);
+                self.print_mac(mac);
                 if style == ast::MacStmtStyle::Semicolon {
-                    self.s.word(";")?;
+                    self.s.word(";");
                 }
             }
         }
         self.maybe_print_trailing_comment(st.span, None)
     }
 
-    crate fn print_block(&mut self, blk: &ast::Block) -> io::Result<()> {
+    crate fn print_block(&mut self, blk: &ast::Block) {
         self.print_block_with_attrs(blk, &[])
     }
 
     crate fn print_block_unclosed_indent(&mut self, blk: &ast::Block,
-                                       indented: usize) -> io::Result<()> {
+                                       indented: usize) {
         self.print_block_maybe_unclosed(blk, indented, &[], false)
     }
 
     crate fn print_block_with_attrs(&mut self,
                                   blk: &ast::Block,
-                                  attrs: &[ast::Attribute]) -> io::Result<()> {
+                                  attrs: &[ast::Attribute]) {
         self.print_block_maybe_unclosed(blk, INDENT_UNIT, attrs, true)
     }
 
@@ -1669,41 +1648,41 @@ impl<'a> State<'a> {
                                       blk: &ast::Block,
                                       indented: usize,
                                       attrs: &[ast::Attribute],
-                                      close_box: bool) -> io::Result<()> {
+                                      close_box: bool) {
         match blk.rules {
-            BlockCheckMode::Unsafe(..) => self.word_space("unsafe")?,
+            BlockCheckMode::Unsafe(..) => self.word_space("unsafe"),
             BlockCheckMode::Default => ()
         }
-        self.maybe_print_comment(blk.span.lo())?;
-        self.ann.pre(self, AnnNode::Block(blk))?;
-        self.bopen()?;
+        self.maybe_print_comment(blk.span.lo());
+        self.ann.pre(self, AnnNode::Block(blk));
+        self.bopen();
 
-        self.print_inner_attributes(attrs)?;
+        self.print_inner_attributes(attrs);
 
         for (i, st) in blk.stmts.iter().enumerate() {
             match st.node {
                 ast::StmtKind::Expr(ref expr) if i == blk.stmts.len() - 1 => {
-                    self.maybe_print_comment(st.span.lo())?;
-                    self.space_if_not_bol()?;
-                    self.print_expr_outer_attr_style(expr, false)?;
-                    self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi()))?;
+                    self.maybe_print_comment(st.span.lo());
+                    self.space_if_not_bol();
+                    self.print_expr_outer_attr_style(expr, false);
+                    self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi()));
                 }
-                _ => self.print_stmt(st)?,
+                _ => self.print_stmt(st),
             }
         }
 
-        self.bclose_maybe_open(blk.span, indented, close_box)?;
+        self.bclose_maybe_open(blk.span, indented, close_box);
         self.ann.post(self, AnnNode::Block(blk))
     }
 
     /// Print a `let pats = scrutinee` expression.
-    crate fn print_let(&mut self, pats: &[P<ast::Pat>], scrutinee: &ast::Expr) -> io::Result<()> {
-        self.s.word("let ")?;
+    crate fn print_let(&mut self, pats: &[P<ast::Pat>], scrutinee: &ast::Expr) {
+        self.s.word("let ");
 
-        self.print_pats(pats)?;
-        self.s.space()?;
+        self.print_pats(pats);
+        self.s.space();
 
-        self.word_space("=")?;
+        self.word_space("=");
         self.print_expr_cond_paren(
             scrutinee,
             Self::cond_needs_par(scrutinee)
@@ -1711,25 +1690,25 @@ impl<'a> State<'a> {
         )
     }
 
-    fn print_else(&mut self, els: Option<&ast::Expr>) -> io::Result<()> {
+    fn print_else(&mut self, els: Option<&ast::Expr>) {
         match els {
             Some(_else) => {
                 match _else.node {
                     // Another `else if` block.
                     ast::ExprKind::If(ref i, ref then, ref e) => {
-                        self.cbox(INDENT_UNIT - 1)?;
-                        self.ibox(0)?;
-                        self.s.word(" else if ")?;
-                        self.print_expr_as_cond(i)?;
-                        self.s.space()?;
-                        self.print_block(then)?;
+                        self.cbox(INDENT_UNIT - 1);
+                        self.ibox(0);
+                        self.s.word(" else if ");
+                        self.print_expr_as_cond(i);
+                        self.s.space();
+                        self.print_block(then);
                         self.print_else(e.as_ref().map(|e| &**e))
                     }
                     // Final `else` block.
                     ast::ExprKind::Block(ref b, _) => {
-                        self.cbox(INDENT_UNIT - 1)?;
-                        self.ibox(0)?;
-                        self.s.word(" else ")?;
+                        self.cbox(INDENT_UNIT - 1);
+                        self.ibox(0);
+                        self.s.word(" else ");
                         self.print_block(b)
                     }
                     // Constraints would be great here!
@@ -1738,33 +1717,33 @@ impl<'a> State<'a> {
                     }
                 }
             }
-            _ => Ok(())
+            _ => {}
         }
     }
 
     crate fn print_if(&mut self, test: &ast::Expr, blk: &ast::Block,
-                    elseopt: Option<&ast::Expr>) -> io::Result<()> {
-        self.head("if")?;
+                    elseopt: Option<&ast::Expr>) {
+        self.head("if");
 
-        self.print_expr_as_cond(test)?;
-        self.s.space()?;
+        self.print_expr_as_cond(test);
+        self.s.space();
 
-        self.print_block(blk)?;
+        self.print_block(blk);
         self.print_else(elseopt)
     }
 
-    crate fn print_mac(&mut self, m: &ast::Mac) -> io::Result<()> {
-        self.print_path(&m.node.path, false, 0)?;
-        self.s.word("!")?;
+    crate fn print_mac(&mut self, m: &ast::Mac) {
+        self.print_path(&m.node.path, false, 0);
+        self.s.word("!");
         match m.node.delim {
-            MacDelimiter::Parenthesis => self.popen()?,
-            MacDelimiter::Bracket => self.s.word("[")?,
+            MacDelimiter::Parenthesis => self.popen(),
+            MacDelimiter::Bracket => self.s.word("["),
             MacDelimiter::Brace => {
-                self.head("")?;
-                self.bopen()?;
+                self.head("");
+                self.bopen();
             }
         }
-        self.print_tts(m.node.stream())?;
+        self.print_tts(m.node.stream());
         match m.node.delim {
             MacDelimiter::Parenthesis => self.pclose(),
             MacDelimiter::Bracket => self.s.word("]"),
@@ -1773,19 +1752,19 @@ impl<'a> State<'a> {
     }
 
 
-    fn print_call_post(&mut self, args: &[P<ast::Expr>]) -> io::Result<()> {
-        self.popen()?;
-        self.commasep_exprs(Inconsistent, args)?;
+    fn print_call_post(&mut self, args: &[P<ast::Expr>]) {
+        self.popen();
+        self.commasep_exprs(Inconsistent, args);
         self.pclose()
     }
 
-    crate fn print_expr_maybe_paren(&mut self, expr: &ast::Expr, prec: i8) -> io::Result<()> {
+    crate fn print_expr_maybe_paren(&mut self, expr: &ast::Expr, prec: i8) {
         self.print_expr_cond_paren(expr, expr.precedence().order() < prec)
     }
 
     /// Print an expr using syntax that's acceptable in a condition position, such as the `cond` in
     /// `if cond { ... }`.
-    crate fn print_expr_as_cond(&mut self, expr: &ast::Expr) -> io::Result<()> {
+    crate fn print_expr_as_cond(&mut self, expr: &ast::Expr) {
         self.print_expr_cond_paren(expr, Self::cond_needs_par(expr))
     }
 
@@ -1803,114 +1782,112 @@ impl<'a> State<'a> {
     }
 
     /// Print `expr` or `(expr)` when `needs_par` holds.
-    fn print_expr_cond_paren(&mut self, expr: &ast::Expr, needs_par: bool) -> io::Result<()> {
+    fn print_expr_cond_paren(&mut self, expr: &ast::Expr, needs_par: bool) {
         if needs_par {
-            self.popen()?;
+            self.popen();
         }
-        self.print_expr(expr)?;
+        self.print_expr(expr);
         if needs_par {
-            self.pclose()?;
+            self.pclose();
         }
-        Ok(())
     }
 
     fn print_expr_vec(&mut self, exprs: &[P<ast::Expr>],
-                      attrs: &[Attribute]) -> io::Result<()> {
-        self.ibox(INDENT_UNIT)?;
-        self.s.word("[")?;
-        self.print_inner_attributes_inline(attrs)?;
-        self.commasep_exprs(Inconsistent, &exprs[..])?;
-        self.s.word("]")?;
-        self.end()
+                      attrs: &[Attribute]) {
+        self.ibox(INDENT_UNIT);
+        self.s.word("[");
+        self.print_inner_attributes_inline(attrs);
+        self.commasep_exprs(Inconsistent, &exprs[..]);
+        self.s.word("]");
+        self.end();
     }
 
     fn print_expr_repeat(&mut self,
                          element: &ast::Expr,
                          count: &ast::AnonConst,
-                         attrs: &[Attribute]) -> io::Result<()> {
-        self.ibox(INDENT_UNIT)?;
-        self.s.word("[")?;
-        self.print_inner_attributes_inline(attrs)?;
-        self.print_expr(element)?;
-        self.word_space(";")?;
-        self.print_expr(&count.value)?;
-        self.s.word("]")?;
-        self.end()
+                         attrs: &[Attribute]) {
+        self.ibox(INDENT_UNIT);
+        self.s.word("[");
+        self.print_inner_attributes_inline(attrs);
+        self.print_expr(element);
+        self.word_space(";");
+        self.print_expr(&count.value);
+        self.s.word("]");
+        self.end();
     }
 
     fn print_expr_struct(&mut self,
                          path: &ast::Path,
                          fields: &[ast::Field],
                          wth: &Option<P<ast::Expr>>,
-                         attrs: &[Attribute]) -> io::Result<()> {
-        self.print_path(path, true, 0)?;
-        self.s.word("{")?;
-        self.print_inner_attributes_inline(attrs)?;
+                         attrs: &[Attribute]) {
+        self.print_path(path, true, 0);
+        self.s.word("{");
+        self.print_inner_attributes_inline(attrs);
         self.commasep_cmnt(
             Consistent,
             &fields[..],
             |s, field| {
-                s.ibox(INDENT_UNIT)?;
+                s.ibox(INDENT_UNIT);
                 if !field.is_shorthand {
-                    s.print_ident(field.ident)?;
-                    s.word_space(":")?;
+                    s.print_ident(field.ident);
+                    s.word_space(":");
                 }
-                s.print_expr(&field.expr)?;
-                s.end()
+                s.print_expr(&field.expr);
+                s.end();
             },
-            |f| f.span)?;
+            |f| f.span);
         match *wth {
             Some(ref expr) => {
-                self.ibox(INDENT_UNIT)?;
+                self.ibox(INDENT_UNIT);
                 if !fields.is_empty() {
-                    self.s.word(",")?;
-                    self.s.space()?;
+                    self.s.word(",");
+                    self.s.space();
                 }
-                self.s.word("..")?;
-                self.print_expr(expr)?;
-                self.end()?;
+                self.s.word("..");
+                self.print_expr(expr);
+                self.end();
             }
             _ => if !fields.is_empty() {
-                self.s.word(",")?
+                self.s.word(",")
             }
         }
-        self.s.word("}")?;
-        Ok(())
+        self.s.word("}");
     }
 
     fn print_expr_tup(&mut self, exprs: &[P<ast::Expr>],
-                      attrs: &[Attribute]) -> io::Result<()> {
-        self.popen()?;
-        self.print_inner_attributes_inline(attrs)?;
-        self.commasep_exprs(Inconsistent, &exprs[..])?;
+                      attrs: &[Attribute]) {
+        self.popen();
+        self.print_inner_attributes_inline(attrs);
+        self.commasep_exprs(Inconsistent, &exprs[..]);
         if exprs.len() == 1 {
-            self.s.word(",")?;
+            self.s.word(",");
         }
         self.pclose()
     }
 
     fn print_expr_call(&mut self,
                        func: &ast::Expr,
-                       args: &[P<ast::Expr>]) -> io::Result<()> {
+                       args: &[P<ast::Expr>]) {
         let prec =
             match func.node {
                 ast::ExprKind::Field(..) => parser::PREC_FORCE_PAREN,
                 _ => parser::PREC_POSTFIX,
             };
 
-        self.print_expr_maybe_paren(func, prec)?;
+        self.print_expr_maybe_paren(func, prec);
         self.print_call_post(args)
     }
 
     fn print_expr_method_call(&mut self,
                               segment: &ast::PathSegment,
-                              args: &[P<ast::Expr>]) -> io::Result<()> {
+                              args: &[P<ast::Expr>]) {
         let base_args = &args[1..];
-        self.print_expr_maybe_paren(&args[0], parser::PREC_POSTFIX)?;
-        self.s.word(".")?;
-        self.print_ident(segment.ident)?;
+        self.print_expr_maybe_paren(&args[0], parser::PREC_POSTFIX);
+        self.s.word(".");
+        self.print_ident(segment.ident);
         if let Some(ref args) = segment.args {
-            self.print_generic_args(args, true)?;
+            self.print_generic_args(args, true);
         }
         self.print_call_post(base_args)
     }
@@ -1918,7 +1895,7 @@ impl<'a> State<'a> {
     fn print_expr_binary(&mut self,
                          op: ast::BinOp,
                          lhs: &ast::Expr,
-                         rhs: &ast::Expr) -> io::Result<()> {
+                         rhs: &ast::Expr) {
         let assoc_op = AssocOp::from_ast_binop(op.node);
         let prec = assoc_op.precedence() as i8;
         let fixity = assoc_op.fixity();
@@ -1949,217 +1926,217 @@ impl<'a> State<'a> {
             _ => left_prec,
         };
 
-        self.print_expr_maybe_paren(lhs, left_prec)?;
-        self.s.space()?;
-        self.word_space(op.node.to_string())?;
+        self.print_expr_maybe_paren(lhs, left_prec);
+        self.s.space();
+        self.word_space(op.node.to_string());
         self.print_expr_maybe_paren(rhs, right_prec)
     }
 
     fn print_expr_unary(&mut self,
                         op: ast::UnOp,
-                        expr: &ast::Expr) -> io::Result<()> {
-        self.s.word(ast::UnOp::to_string(op))?;
+                        expr: &ast::Expr) {
+        self.s.word(ast::UnOp::to_string(op));
         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
     }
 
     fn print_expr_addr_of(&mut self,
                           mutability: ast::Mutability,
-                          expr: &ast::Expr) -> io::Result<()> {
-        self.s.word("&")?;
-        self.print_mutability(mutability)?;
+                          expr: &ast::Expr) {
+        self.s.word("&");
+        self.print_mutability(mutability);
         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
     }
 
-    crate fn print_expr(&mut self, expr: &ast::Expr) -> io::Result<()> {
+    crate fn print_expr(&mut self, expr: &ast::Expr) {
         self.print_expr_outer_attr_style(expr, true)
     }
 
     fn print_expr_outer_attr_style(&mut self,
                                   expr: &ast::Expr,
-                                  is_inline: bool) -> io::Result<()> {
-        self.maybe_print_comment(expr.span.lo())?;
+                                  is_inline: bool) {
+        self.maybe_print_comment(expr.span.lo());
 
         let attrs = &expr.attrs;
         if is_inline {
-            self.print_outer_attributes_inline(attrs)?;
+            self.print_outer_attributes_inline(attrs);
         } else {
-            self.print_outer_attributes(attrs)?;
+            self.print_outer_attributes(attrs);
         }
 
-        self.ibox(INDENT_UNIT)?;
-        self.ann.pre(self, AnnNode::Expr(expr))?;
+        self.ibox(INDENT_UNIT);
+        self.ann.pre(self, AnnNode::Expr(expr));
         match expr.node {
             ast::ExprKind::Box(ref expr) => {
-                self.word_space("box")?;
-                self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)?;
+                self.word_space("box");
+                self.print_expr_maybe_paren(expr, parser::PREC_PREFIX);
             }
             ast::ExprKind::Array(ref exprs) => {
-                self.print_expr_vec(&exprs[..], attrs)?;
+                self.print_expr_vec(&exprs[..], attrs);
             }
             ast::ExprKind::Repeat(ref element, ref count) => {
-                self.print_expr_repeat(element, count, attrs)?;
+                self.print_expr_repeat(element, count, attrs);
             }
             ast::ExprKind::Struct(ref path, ref fields, ref wth) => {
-                self.print_expr_struct(path, &fields[..], wth, attrs)?;
+                self.print_expr_struct(path, &fields[..], wth, attrs);
             }
             ast::ExprKind::Tup(ref exprs) => {
-                self.print_expr_tup(&exprs[..], attrs)?;
+                self.print_expr_tup(&exprs[..], attrs);
             }
             ast::ExprKind::Call(ref func, ref args) => {
-                self.print_expr_call(func, &args[..])?;
+                self.print_expr_call(func, &args[..]);
             }
             ast::ExprKind::MethodCall(ref segment, ref args) => {
-                self.print_expr_method_call(segment, &args[..])?;
+                self.print_expr_method_call(segment, &args[..]);
             }
             ast::ExprKind::Binary(op, ref lhs, ref rhs) => {
-                self.print_expr_binary(op, lhs, rhs)?;
+                self.print_expr_binary(op, lhs, rhs);
             }
             ast::ExprKind::Unary(op, ref expr) => {
-                self.print_expr_unary(op, expr)?;
+                self.print_expr_unary(op, expr);
             }
             ast::ExprKind::AddrOf(m, ref expr) => {
-                self.print_expr_addr_of(m, expr)?;
+                self.print_expr_addr_of(m, expr);
             }
             ast::ExprKind::Lit(ref lit) => {
-                self.print_literal(lit)?;
+                self.print_literal(lit);
             }
             ast::ExprKind::Cast(ref expr, ref ty) => {
                 let prec = AssocOp::As.precedence() as i8;
-                self.print_expr_maybe_paren(expr, prec)?;
-                self.s.space()?;
-                self.word_space("as")?;
-                self.print_type(ty)?;
+                self.print_expr_maybe_paren(expr, prec);
+                self.s.space();
+                self.word_space("as");
+                self.print_type(ty);
             }
             ast::ExprKind::Type(ref expr, ref ty) => {
                 let prec = AssocOp::Colon.precedence() as i8;
-                self.print_expr_maybe_paren(expr, prec)?;
-                self.word_space(":")?;
-                self.print_type(ty)?;
+                self.print_expr_maybe_paren(expr, prec);
+                self.word_space(":");
+                self.print_type(ty);
             }
             ast::ExprKind::Let(ref pats, ref scrutinee) => {
-                self.print_let(pats, scrutinee)?;
+                self.print_let(pats, scrutinee);
             }
             ast::ExprKind::If(ref test, ref blk, ref elseopt) => {
-                self.print_if(test, blk, elseopt.as_ref().map(|e| &**e))?;
+                self.print_if(test, blk, elseopt.as_ref().map(|e| &**e));
             }
             ast::ExprKind::While(ref test, ref blk, opt_label) => {
                 if let Some(label) = opt_label {
-                    self.print_ident(label.ident)?;
-                    self.word_space(":")?;
+                    self.print_ident(label.ident);
+                    self.word_space(":");
                 }
-                self.head("while")?;
-                self.print_expr_as_cond(test)?;
-                self.s.space()?;
-                self.print_block_with_attrs(blk, attrs)?;
+                self.head("while");
+                self.print_expr_as_cond(test);
+                self.s.space();
+                self.print_block_with_attrs(blk, attrs);
             }
             ast::ExprKind::ForLoop(ref pat, ref iter, ref blk, opt_label) => {
                 if let Some(label) = opt_label {
-                    self.print_ident(label.ident)?;
-                    self.word_space(":")?;
+                    self.print_ident(label.ident);
+                    self.word_space(":");
                 }
-                self.head("for")?;
-                self.print_pat(pat)?;
-                self.s.space()?;
-                self.word_space("in")?;
-                self.print_expr_as_cond(iter)?;
-                self.s.space()?;
-                self.print_block_with_attrs(blk, attrs)?;
+                self.head("for");
+                self.print_pat(pat);
+                self.s.space();
+                self.word_space("in");
+                self.print_expr_as_cond(iter);
+                self.s.space();
+                self.print_block_with_attrs(blk, attrs);
             }
             ast::ExprKind::Loop(ref blk, opt_label) => {
                 if let Some(label) = opt_label {
-                    self.print_ident(label.ident)?;
-                    self.word_space(":")?;
+                    self.print_ident(label.ident);
+                    self.word_space(":");
                 }
-                self.head("loop")?;
-                self.s.space()?;
-                self.print_block_with_attrs(blk, attrs)?;
+                self.head("loop");
+                self.s.space();
+                self.print_block_with_attrs(blk, attrs);
             }
             ast::ExprKind::Match(ref expr, ref arms) => {
-                self.cbox(INDENT_UNIT)?;
-                self.ibox(4)?;
-                self.word_nbsp("match")?;
-                self.print_expr_as_cond(expr)?;
-                self.s.space()?;
-                self.bopen()?;
-                self.print_inner_attributes_no_trailing_hardbreak(attrs)?;
+                self.cbox(INDENT_UNIT);
+                self.ibox(4);
+                self.word_nbsp("match");
+                self.print_expr_as_cond(expr);
+                self.s.space();
+                self.bopen();
+                self.print_inner_attributes_no_trailing_hardbreak(attrs);
                 for arm in arms {
-                    self.print_arm(arm)?;
+                    self.print_arm(arm);
                 }
-                self.bclose_(expr.span, INDENT_UNIT)?;
+                self.bclose_(expr.span, INDENT_UNIT);
             }
             ast::ExprKind::Closure(
                 capture_clause, asyncness, movability, ref decl, ref body, _) => {
-                self.print_movability(movability)?;
-                self.print_asyncness(asyncness)?;
-                self.print_capture_clause(capture_clause)?;
+                self.print_movability(movability);
+                self.print_asyncness(asyncness);
+                self.print_capture_clause(capture_clause);
 
-                self.print_fn_block_args(decl)?;
-                self.s.space()?;
-                self.print_expr(body)?;
-                self.end()?; // need to close a box
+                self.print_fn_block_args(decl);
+                self.s.space();
+                self.print_expr(body);
+                self.end(); // need to close a box
 
                 // a box will be closed by print_expr, but we didn't want an overall
                 // wrapper so we closed the corresponding opening. so create an
                 // empty box to satisfy the close.
-                self.ibox(0)?;
+                self.ibox(0);
             }
             ast::ExprKind::Block(ref blk, opt_label) => {
                 if let Some(label) = opt_label {
-                    self.print_ident(label.ident)?;
-                    self.word_space(":")?;
+                    self.print_ident(label.ident);
+                    self.word_space(":");
                 }
                 // containing cbox, will be closed by print-block at }
-                self.cbox(INDENT_UNIT)?;
+                self.cbox(INDENT_UNIT);
                 // head-box, will be closed by print-block after {
-                self.ibox(0)?;
-                self.print_block_with_attrs(blk, attrs)?;
+                self.ibox(0);
+                self.print_block_with_attrs(blk, attrs);
             }
             ast::ExprKind::Async(capture_clause, _, ref blk) => {
-                self.word_nbsp("async")?;
-                self.print_capture_clause(capture_clause)?;
-                self.s.space()?;
+                self.word_nbsp("async");
+                self.print_capture_clause(capture_clause);
+                self.s.space();
                 // cbox/ibox in analogy to the `ExprKind::Block` arm above
-                self.cbox(INDENT_UNIT)?;
-                self.ibox(0)?;
-                self.print_block_with_attrs(blk, attrs)?;
+                self.cbox(INDENT_UNIT);
+                self.ibox(0);
+                self.print_block_with_attrs(blk, attrs);
             }
             ast::ExprKind::Await(origin, ref expr) => {
                 match origin {
                     ast::AwaitOrigin::MacroLike => {
-                        self.s.word("await!")?;
-                        self.print_expr_maybe_paren(expr, parser::PREC_FORCE_PAREN)?;
+                        self.s.word("await!");
+                        self.print_expr_maybe_paren(expr, parser::PREC_FORCE_PAREN);
                     }
                     ast::AwaitOrigin::FieldLike => {
-                        self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX)?;
-                        self.s.word(".await")?;
+                        self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
+                        self.s.word(".await");
                     }
                 }
             }
             ast::ExprKind::Assign(ref lhs, ref rhs) => {
                 let prec = AssocOp::Assign.precedence() as i8;
-                self.print_expr_maybe_paren(lhs, prec + 1)?;
-                self.s.space()?;
-                self.word_space("=")?;
-                self.print_expr_maybe_paren(rhs, prec)?;
+                self.print_expr_maybe_paren(lhs, prec + 1);
+                self.s.space();
+                self.word_space("=");
+                self.print_expr_maybe_paren(rhs, prec);
             }
             ast::ExprKind::AssignOp(op, ref lhs, ref rhs) => {
                 let prec = AssocOp::Assign.precedence() as i8;
-                self.print_expr_maybe_paren(lhs, prec + 1)?;
-                self.s.space()?;
-                self.s.word(op.node.to_string())?;
-                self.word_space("=")?;
-                self.print_expr_maybe_paren(rhs, prec)?;
+                self.print_expr_maybe_paren(lhs, prec + 1);
+                self.s.space();
+                self.s.word(op.node.to_string());
+                self.word_space("=");
+                self.print_expr_maybe_paren(rhs, prec);
             }
             ast::ExprKind::Field(ref expr, ident) => {
-                self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX)?;
-                self.s.word(".")?;
-                self.print_ident(ident)?;
+                self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
+                self.s.word(".");
+                self.print_ident(ident);
             }
             ast::ExprKind::Index(ref expr, ref index) => {
-                self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX)?;
-                self.s.word("[")?;
-                self.print_expr(index)?;
-                self.s.word("]")?;
+                self.print_expr_maybe_paren(expr, parser::PREC_POSTFIX);
+                self.s.word("[");
+                self.print_expr(index);
+                self.s.word("]");
             }
             ast::ExprKind::Range(ref start, ref end, limits) => {
                 // Special case for `Range`.  `AssocOp` claims that `Range` has higher precedence
@@ -2168,55 +2145,55 @@ impl<'a> State<'a> {
                 // a "normal" binop gets parenthesized.  (`LOr` is the lowest-precedence binop.)
                 let fake_prec = AssocOp::LOr.precedence() as i8;
                 if let Some(ref e) = *start {
-                    self.print_expr_maybe_paren(e, fake_prec)?;
+                    self.print_expr_maybe_paren(e, fake_prec);
                 }
                 if limits == ast::RangeLimits::HalfOpen {
-                    self.s.word("..")?;
+                    self.s.word("..");
                 } else {
-                    self.s.word("..=")?;
+                    self.s.word("..=");
                 }
                 if let Some(ref e) = *end {
-                    self.print_expr_maybe_paren(e, fake_prec)?;
+                    self.print_expr_maybe_paren(e, fake_prec);
                 }
             }
             ast::ExprKind::Path(None, ref path) => {
-                self.print_path(path, true, 0)?
+                self.print_path(path, true, 0)
             }
             ast::ExprKind::Path(Some(ref qself), ref path) => {
-                self.print_qpath(path, qself, true)?
+                self.print_qpath(path, qself, true)
             }
             ast::ExprKind::Break(opt_label, ref opt_expr) => {
-                self.s.word("break")?;
-                self.s.space()?;
+                self.s.word("break");
+                self.s.space();
                 if let Some(label) = opt_label {
-                    self.print_ident(label.ident)?;
-                    self.s.space()?;
+                    self.print_ident(label.ident);
+                    self.s.space();
                 }
                 if let Some(ref expr) = *opt_expr {
-                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP)?;
-                    self.s.space()?;
+                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
+                    self.s.space();
                 }
             }
             ast::ExprKind::Continue(opt_label) => {
-                self.s.word("continue")?;
-                self.s.space()?;
+                self.s.word("continue");
+                self.s.space();
                 if let Some(label) = opt_label {
-                    self.print_ident(label.ident)?;
-                    self.s.space()?
+                    self.print_ident(label.ident);
+                    self.s.space()
                 }
             }
             ast::ExprKind::Ret(ref result) => {
-                self.s.word("return")?;
+                self.s.word("return");
                 if let Some(ref expr) = *result {
-                    self.s.word(" ")?;
-                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP)?;
+                    self.s.word(" ");
+                    self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
                 }
             }
             ast::ExprKind::InlineAsm(ref a) => {
-                self.s.word("asm!")?;
-                self.popen()?;
-                self.print_string(&a.asm.as_str(), a.asm_str_style)?;
-                self.word_space(":")?;
+                self.s.word("asm!");
+                self.popen();
+                self.print_string(&a.asm.as_str(), a.asm_str_style);
+                self.word_space(":");
 
                 self.commasep(Inconsistent, &a.outputs, |s, out| {
                     let constraint = out.constraint.as_str();
@@ -2224,33 +2201,30 @@ impl<'a> State<'a> {
                     match ch.next() {
                         Some('=') if out.is_rw => {
                             s.print_string(&format!("+{}", ch.as_str()),
-                                           ast::StrStyle::Cooked)?
+                                           ast::StrStyle::Cooked)
                         }
-                        _ => s.print_string(&constraint, ast::StrStyle::Cooked)?
+                        _ => s.print_string(&constraint, ast::StrStyle::Cooked)
                     }
-                    s.popen()?;
-                    s.print_expr(&out.expr)?;
-                    s.pclose()?;
-                    Ok(())
-                })?;
-                self.s.space()?;
-                self.word_space(":")?;
+                    s.popen();
+                    s.print_expr(&out.expr);
+                    s.pclose();
+                });
+                self.s.space();
+                self.word_space(":");
 
                 self.commasep(Inconsistent, &a.inputs, |s, &(co, ref o)| {
-                    s.print_string(&co.as_str(), ast::StrStyle::Cooked)?;
-                    s.popen()?;
-                    s.print_expr(o)?;
-                    s.pclose()?;
-                    Ok(())
-                })?;
-                self.s.space()?;
-                self.word_space(":")?;
+                    s.print_string(&co.as_str(), ast::StrStyle::Cooked);
+                    s.popen();
+                    s.print_expr(o);
+                    s.pclose();
+                });
+                self.s.space();
+                self.word_space(":");
 
                 self.commasep(Inconsistent, &a.clobbers,
                                    |s, co| {
-                    s.print_string(&co.as_str(), ast::StrStyle::Cooked)?;
-                    Ok(())
-                })?;
+                    s.print_string(&co.as_str(), ast::StrStyle::Cooked);
+                });
 
                 let mut options = vec![];
                 if a.volatile {
@@ -2264,415 +2238,401 @@ impl<'a> State<'a> {
                 }
 
                 if !options.is_empty() {
-                    self.s.space()?;
-                    self.word_space(":")?;
+                    self.s.space();
+                    self.word_space(":");
                     self.commasep(Inconsistent, &options,
                                   |s, &co| {
-                                      s.print_string(co, ast::StrStyle::Cooked)?;
-                                      Ok(())
-                                  })?;
+                                      s.print_string(co, ast::StrStyle::Cooked);
+                                  });
                 }
 
-                self.pclose()?;
+                self.pclose();
             }
-            ast::ExprKind::Mac(ref m) => self.print_mac(m)?,
+            ast::ExprKind::Mac(ref m) => self.print_mac(m),
             ast::ExprKind::Paren(ref e) => {
-                self.popen()?;
-                self.print_inner_attributes_inline(attrs)?;
-                self.print_expr(e)?;
-                self.pclose()?;
+                self.popen();
+                self.print_inner_attributes_inline(attrs);
+                self.print_expr(e);
+                self.pclose();
             },
             ast::ExprKind::Yield(ref e) => {
-                self.s.word("yield")?;
+                self.s.word("yield");
                 match *e {
                     Some(ref expr) => {
-                        self.s.space()?;
-                        self.print_expr_maybe_paren(expr, parser::PREC_JUMP)?;
+                        self.s.space();
+                        self.print_expr_maybe_paren(expr, parser::PREC_JUMP);
                     }
                     _ => ()
                 }
             }
             ast::ExprKind::Try(ref e) => {
-                self.print_expr_maybe_paren(e, parser::PREC_POSTFIX)?;
-                self.s.word("?")?
+                self.print_expr_maybe_paren(e, parser::PREC_POSTFIX);
+                self.s.word("?")
             }
             ast::ExprKind::TryBlock(ref blk) => {
-                self.head("try")?;
-                self.s.space()?;
-                self.print_block_with_attrs(blk, attrs)?
+                self.head("try");
+                self.s.space();
+                self.print_block_with_attrs(blk, attrs)
             }
             ast::ExprKind::Err => {
-                self.popen()?;
-                self.s.word("/*ERROR*/")?;
-                self.pclose()?
+                self.popen();
+                self.s.word("/*ERROR*/");
+                self.pclose()
             }
         }
-        self.ann.post(self, AnnNode::Expr(expr))?;
-        self.end()
+        self.ann.post(self, AnnNode::Expr(expr));
+        self.end();
     }
 
-    crate fn print_local_decl(&mut self, loc: &ast::Local) -> io::Result<()> {
-        self.print_pat(&loc.pat)?;
+    crate fn print_local_decl(&mut self, loc: &ast::Local) {
+        self.print_pat(&loc.pat);
         if let Some(ref ty) = loc.ty {
-            self.word_space(":")?;
-            self.print_type(ty)?;
+            self.word_space(":");
+            self.print_type(ty);
         }
-        Ok(())
     }
 
-    crate fn print_ident(&mut self, ident: ast::Ident) -> io::Result<()> {
+    crate fn print_ident(&mut self, ident: ast::Ident) {
         if ident.is_raw_guess() {
-            self.s.word(format!("r#{}", ident))?;
+            self.s.word(format!("r#{}", ident));
         } else {
-            self.s.word(ident.as_str().to_string())?;
+            self.s.word(ident.as_str().to_string());
         }
         self.ann.post(self, AnnNode::Ident(&ident))
     }
 
-    crate fn print_usize(&mut self, i: usize) -> io::Result<()> {
+    crate fn print_usize(&mut self, i: usize) {
         self.s.word(i.to_string())
     }
 
-    crate fn print_name(&mut self, name: ast::Name) -> io::Result<()> {
-        self.s.word(name.as_str().to_string())?;
+    crate fn print_name(&mut self, name: ast::Name) {
+        self.s.word(name.as_str().to_string());
         self.ann.post(self, AnnNode::Name(&name))
     }
 
     fn print_path(&mut self,
                   path: &ast::Path,
                   colons_before_params: bool,
-                  depth: usize)
-                  -> io::Result<()>
-    {
-        self.maybe_print_comment(path.span.lo())?;
+                  depth: usize) {
+        self.maybe_print_comment(path.span.lo());
 
         for (i, segment) in path.segments[..path.segments.len() - depth].iter().enumerate() {
             if i > 0 {
-                self.s.word("::")?
+                self.s.word("::")
             }
-            self.print_path_segment(segment, colons_before_params)?;
+            self.print_path_segment(segment, colons_before_params);
         }
-
-        Ok(())
     }
 
     fn print_path_segment(&mut self,
                           segment: &ast::PathSegment,
-                          colons_before_params: bool)
-                          -> io::Result<()>
-    {
+                          colons_before_params: bool) {
         if segment.ident.name != kw::PathRoot {
             if segment.ident.name == kw::DollarCrate {
-                self.print_dollar_crate(segment.ident)?;
+                self.print_dollar_crate(segment.ident);
             } else {
-                self.print_ident(segment.ident)?;
+                self.print_ident(segment.ident);
             }
             if let Some(ref args) = segment.args {
-                self.print_generic_args(args, colons_before_params)?;
+                self.print_generic_args(args, colons_before_params);
             }
         }
-        Ok(())
     }
 
     fn print_qpath(&mut self,
                    path: &ast::Path,
                    qself: &ast::QSelf,
                    colons_before_params: bool)
-                   -> io::Result<()>
     {
-        self.s.word("<")?;
-        self.print_type(&qself.ty)?;
+        self.s.word("<");
+        self.print_type(&qself.ty);
         if qself.position > 0 {
-            self.s.space()?;
-            self.word_space("as")?;
+            self.s.space();
+            self.word_space("as");
             let depth = path.segments.len() - qself.position;
-            self.print_path(path, false, depth)?;
+            self.print_path(path, false, depth);
         }
-        self.s.word(">")?;
-        self.s.word("::")?;
+        self.s.word(">");
+        self.s.word("::");
         let item_segment = path.segments.last().unwrap();
-        self.print_ident(item_segment.ident)?;
+        self.print_ident(item_segment.ident);
         match item_segment.args {
             Some(ref args) => self.print_generic_args(args, colons_before_params),
-            None => Ok(()),
+            None => {},
         }
     }
 
     fn print_generic_args(&mut self,
                           args: &ast::GenericArgs,
                           colons_before_params: bool)
-                          -> io::Result<()>
     {
         if colons_before_params {
-            self.s.word("::")?
+            self.s.word("::")
         }
 
         match *args {
             ast::GenericArgs::AngleBracketed(ref data) => {
-                self.s.word("<")?;
+                self.s.word("<");
 
                 self.commasep(Inconsistent, &data.args, |s, generic_arg| {
                     s.print_generic_arg(generic_arg)
-                })?;
+                });
 
                 let mut comma = data.args.len() != 0;
 
                 for constraint in data.constraints.iter() {
                     if comma {
-                        self.word_space(",")?
+                        self.word_space(",")
                     }
-                    self.print_ident(constraint.ident)?;
-                    self.s.space()?;
+                    self.print_ident(constraint.ident);
+                    self.s.space();
                     match constraint.kind {
                         ast::AssocTyConstraintKind::Equality { ref ty } => {
-                            self.word_space("=")?;
-                            self.print_type(ty)?;
+                            self.word_space("=");
+                            self.print_type(ty);
                         }
                         ast::AssocTyConstraintKind::Bound { ref bounds } => {
-                            self.print_type_bounds(":", &*bounds)?;
+                            self.print_type_bounds(":", &*bounds);
                         }
                     }
                     comma = true;
                 }
 
-                self.s.word(">")?
+                self.s.word(">")
             }
 
             ast::GenericArgs::Parenthesized(ref data) => {
-                self.s.word("(")?;
+                self.s.word("(");
                 self.commasep(
                     Inconsistent,
                     &data.inputs,
-                    |s, ty| s.print_type(ty))?;
-                self.s.word(")")?;
+                    |s, ty| s.print_type(ty));
+                self.s.word(")");
 
                 if let Some(ref ty) = data.output {
-                    self.space_if_not_bol()?;
-                    self.word_space("->")?;
-                    self.print_type(ty)?;
+                    self.space_if_not_bol();
+                    self.word_space("->");
+                    self.print_type(ty);
                 }
             }
         }
-
-        Ok(())
     }
 
-    crate fn print_pat(&mut self, pat: &ast::Pat) -> io::Result<()> {
-        self.maybe_print_comment(pat.span.lo())?;
-        self.ann.pre(self, AnnNode::Pat(pat))?;
+    crate fn print_pat(&mut self, pat: &ast::Pat) {
+        self.maybe_print_comment(pat.span.lo());
+        self.ann.pre(self, AnnNode::Pat(pat));
         /* Pat isn't normalized, but the beauty of it
          is that it doesn't matter */
         match pat.node {
-            PatKind::Wild => self.s.word("_")?,
+            PatKind::Wild => self.s.word("_"),
             PatKind::Ident(binding_mode, ident, ref sub) => {
                 match binding_mode {
                     ast::BindingMode::ByRef(mutbl) => {
-                        self.word_nbsp("ref")?;
-                        self.print_mutability(mutbl)?;
+                        self.word_nbsp("ref");
+                        self.print_mutability(mutbl);
                     }
                     ast::BindingMode::ByValue(ast::Mutability::Immutable) => {}
                     ast::BindingMode::ByValue(ast::Mutability::Mutable) => {
-                        self.word_nbsp("mut")?;
+                        self.word_nbsp("mut");
                     }
                 }
-                self.print_ident(ident)?;
+                self.print_ident(ident);
                 if let Some(ref p) = *sub {
-                    self.s.word("@")?;
-                    self.print_pat(p)?;
+                    self.s.word("@");
+                    self.print_pat(p);
                 }
             }
             PatKind::TupleStruct(ref path, ref elts, ddpos) => {
-                self.print_path(path, true, 0)?;
-                self.popen()?;
+                self.print_path(path, true, 0);
+                self.popen();
                 if let Some(ddpos) = ddpos {
-                    self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(p))?;
+                    self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(p));
                     if ddpos != 0 {
-                        self.word_space(",")?;
+                        self.word_space(",");
                     }
-                    self.s.word("..")?;
+                    self.s.word("..");
                     if ddpos != elts.len() {
-                        self.s.word(",")?;
-                        self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(p))?;
+                        self.s.word(",");
+                        self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(p));
                     }
                 } else {
-                    self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(p))?;
+                    self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(p));
                 }
-                self.pclose()?;
+                self.pclose();
             }
             PatKind::Path(None, ref path) => {
-                self.print_path(path, true, 0)?;
+                self.print_path(path, true, 0);
             }
             PatKind::Path(Some(ref qself), ref path) => {
-                self.print_qpath(path, qself, false)?;
+                self.print_qpath(path, qself, false);
             }
             PatKind::Struct(ref path, ref fields, etc) => {
-                self.print_path(path, true, 0)?;
-                self.nbsp()?;
-                self.word_space("{")?;
+                self.print_path(path, true, 0);
+                self.nbsp();
+                self.word_space("{");
                 self.commasep_cmnt(
                     Consistent, &fields[..],
                     |s, f| {
-                        s.cbox(INDENT_UNIT)?;
+                        s.cbox(INDENT_UNIT);
                         if !f.node.is_shorthand {
-                            s.print_ident(f.node.ident)?;
-                            s.word_nbsp(":")?;
+                            s.print_ident(f.node.ident);
+                            s.word_nbsp(":");
                         }
-                        s.print_pat(&f.node.pat)?;
-                        s.end()
+                        s.print_pat(&f.node.pat);
+                        s.end();
                     },
-                    |f| f.node.pat.span)?;
+                    |f| f.node.pat.span);
                 if etc {
-                    if !fields.is_empty() { self.word_space(",")?; }
-                    self.s.word("..")?;
+                    if !fields.is_empty() { self.word_space(","); }
+                    self.s.word("..");
                 }
-                self.s.space()?;
-                self.s.word("}")?;
+                self.s.space();
+                self.s.word("}");
             }
             PatKind::Tuple(ref elts, ddpos) => {
-                self.popen()?;
+                self.popen();
                 if let Some(ddpos) = ddpos {
-                    self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(p))?;
+                    self.commasep(Inconsistent, &elts[..ddpos], |s, p| s.print_pat(p));
                     if ddpos != 0 {
-                        self.word_space(",")?;
+                        self.word_space(",");
                     }
-                    self.s.word("..")?;
+                    self.s.word("..");
                     if ddpos != elts.len() {
-                        self.s.word(",")?;
-                        self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(p))?;
+                        self.s.word(",");
+                        self.commasep(Inconsistent, &elts[ddpos..], |s, p| s.print_pat(p));
                     }
                 } else {
-                    self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(p))?;
+                    self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(p));
                     if elts.len() == 1 {
-                        self.s.word(",")?;
+                        self.s.word(",");
                     }
                 }
-                self.pclose()?;
+                self.pclose();
             }
             PatKind::Box(ref inner) => {
-                self.s.word("box ")?;
-                self.print_pat(inner)?;
+                self.s.word("box ");
+                self.print_pat(inner);
             }
             PatKind::Ref(ref inner, mutbl) => {
-                self.s.word("&")?;
+                self.s.word("&");
                 if mutbl == ast::Mutability::Mutable {
-                    self.s.word("mut ")?;
+                    self.s.word("mut ");
                 }
-                self.print_pat(inner)?;
+                self.print_pat(inner);
             }
-            PatKind::Lit(ref e) => self.print_expr(&**e)?,
+            PatKind::Lit(ref e) => self.print_expr(&**e),
             PatKind::Range(ref begin, ref end, Spanned { node: ref end_kind, .. }) => {
-                self.print_expr(begin)?;
-                self.s.space()?;
+                self.print_expr(begin);
+                self.s.space();
                 match *end_kind {
-                    RangeEnd::Included(RangeSyntax::DotDotDot) => self.s.word("...")?,
-                    RangeEnd::Included(RangeSyntax::DotDotEq) => self.s.word("..=")?,
-                    RangeEnd::Excluded => self.s.word("..")?,
+                    RangeEnd::Included(RangeSyntax::DotDotDot) => self.s.word("..."),
+                    RangeEnd::Included(RangeSyntax::DotDotEq) => self.s.word("..="),
+                    RangeEnd::Excluded => self.s.word(".."),
                 }
-                self.print_expr(end)?;
+                self.print_expr(end);
             }
             PatKind::Slice(ref before, ref slice, ref after) => {
-                self.s.word("[")?;
+                self.s.word("[");
                 self.commasep(Inconsistent,
                                    &before[..],
-                                   |s, p| s.print_pat(p))?;
+                                   |s, p| s.print_pat(p));
                 if let Some(ref p) = *slice {
-                    if !before.is_empty() { self.word_space(",")?; }
+                    if !before.is_empty() { self.word_space(","); }
                     if let PatKind::Wild = p.node {
                         // Print nothing
                     } else {
-                        self.print_pat(p)?;
+                        self.print_pat(p);
                     }
-                    self.s.word("..")?;
-                    if !after.is_empty() { self.word_space(",")?; }
+                    self.s.word("..");
+                    if !after.is_empty() { self.word_space(","); }
                 }
                 self.commasep(Inconsistent,
                                    &after[..],
-                                   |s, p| s.print_pat(p))?;
-                self.s.word("]")?;
+                                   |s, p| s.print_pat(p));
+                self.s.word("]");
             }
             PatKind::Paren(ref inner) => {
-                self.popen()?;
-                self.print_pat(inner)?;
-                self.pclose()?;
+                self.popen();
+                self.print_pat(inner);
+                self.pclose();
             }
-            PatKind::Mac(ref m) => self.print_mac(m)?,
+            PatKind::Mac(ref m) => self.print_mac(m),
         }
         self.ann.post(self, AnnNode::Pat(pat))
     }
 
-    fn print_pats(&mut self, pats: &[P<ast::Pat>]) -> io::Result<()> {
+    fn print_pats(&mut self, pats: &[P<ast::Pat>]) {
         let mut first = true;
         for p in pats {
             if first {
                 first = false;
             } else {
-                self.s.space()?;
-                self.word_space("|")?;
+                self.s.space();
+                self.word_space("|");
             }
-            self.print_pat(p)?;
+            self.print_pat(p);
         }
-        Ok(())
     }
 
-    fn print_arm(&mut self, arm: &ast::Arm) -> io::Result<()> {
+    fn print_arm(&mut self, arm: &ast::Arm) {
         // I have no idea why this check is necessary, but here it
         // is :(
         if arm.attrs.is_empty() {
-            self.s.space()?;
-        }
-        self.cbox(INDENT_UNIT)?;
-        self.ibox(0)?;
-        self.maybe_print_comment(arm.pats[0].span.lo())?;
-        self.print_outer_attributes(&arm.attrs)?;
-        self.print_pats(&arm.pats)?;
-        self.s.space()?;
+            self.s.space();
+        }
+        self.cbox(INDENT_UNIT);
+        self.ibox(0);
+        self.maybe_print_comment(arm.pats[0].span.lo());
+        self.print_outer_attributes(&arm.attrs);
+        self.print_pats(&arm.pats);
+        self.s.space();
         if let Some(ref e) = arm.guard {
-            self.word_space("if")?;
-            self.print_expr(e)?;
-            self.s.space()?;
+            self.word_space("if");
+            self.print_expr(e);
+            self.s.space();
         }
-        self.word_space("=>")?;
+        self.word_space("=>");
 
         match arm.body.node {
             ast::ExprKind::Block(ref blk, opt_label) => {
                 if let Some(label) = opt_label {
-                    self.print_ident(label.ident)?;
-                    self.word_space(":")?;
+                    self.print_ident(label.ident);
+                    self.word_space(":");
                 }
 
                 // the block will close the pattern's ibox
-                self.print_block_unclosed_indent(blk, INDENT_UNIT)?;
+                self.print_block_unclosed_indent(blk, INDENT_UNIT);
 
                 // If it is a user-provided unsafe block, print a comma after it
                 if let BlockCheckMode::Unsafe(ast::UserProvided) = blk.rules {
-                    self.s.word(",")?;
+                    self.s.word(",");
                 }
             }
             _ => {
-                self.end()?; // close the ibox for the pattern
-                self.print_expr(&arm.body)?;
-                self.s.word(",")?;
+                self.end(); // close the ibox for the pattern
+                self.print_expr(&arm.body);
+                self.s.word(",");
             }
         }
-        self.end() // close enclosing cbox
+        self.end(); // close enclosing cbox
     }
 
-    fn print_explicit_self(&mut self, explicit_self: &ast::ExplicitSelf) -> io::Result<()> {
+    fn print_explicit_self(&mut self, explicit_self: &ast::ExplicitSelf) {
         match explicit_self.node {
             SelfKind::Value(m) => {
-                self.print_mutability(m)?;
+                self.print_mutability(m);
                 self.s.word("self")
             }
             SelfKind::Region(ref lt, m) => {
-                self.s.word("&")?;
-                self.print_opt_lifetime(lt)?;
-                self.print_mutability(m)?;
+                self.s.word("&");
+                self.print_opt_lifetime(lt);
+                self.print_mutability(m);
                 self.s.word("self")
             }
             SelfKind::Explicit(ref typ, m) => {
-                self.print_mutability(m)?;
-                self.s.word("self")?;
-                self.word_space(":")?;
+                self.print_mutability(m);
+                self.s.word("self");
+                self.word_space(":");
                 self.print_type(typ)
             }
         }
@@ -2683,184 +2643,167 @@ impl<'a> State<'a> {
                     header: ast::FnHeader,
                     name: Option<ast::Ident>,
                     generics: &ast::Generics,
-                    vis: &ast::Visibility) -> io::Result<()> {
-        self.print_fn_header_info(header, vis)?;
+                    vis: &ast::Visibility) {
+        self.print_fn_header_info(header, vis);
 
         if let Some(name) = name {
-            self.nbsp()?;
-            self.print_ident(name)?;
+            self.nbsp();
+            self.print_ident(name);
         }
-        self.print_generic_params(&generics.params)?;
-        self.print_fn_args_and_ret(decl)?;
+        self.print_generic_params(&generics.params);
+        self.print_fn_args_and_ret(decl);
         self.print_where_clause(&generics.where_clause)
     }
 
-    crate fn print_fn_args_and_ret(&mut self, decl: &ast::FnDecl)
-        -> io::Result<()> {
-        self.popen()?;
-        self.commasep(Inconsistent, &decl.inputs, |s, arg| s.print_arg(arg, false))?;
-        self.pclose()?;
+    crate fn print_fn_args_and_ret(&mut self, decl: &ast::FnDecl) {
+        self.popen();
+        self.commasep(Inconsistent, &decl.inputs, |s, arg| s.print_arg(arg, false));
+        self.pclose();
 
         self.print_fn_output(decl)
     }
 
-    crate fn print_fn_block_args(
-            &mut self,
-            decl: &ast::FnDecl)
-            -> io::Result<()> {
-        self.s.word("|")?;
-        self.commasep(Inconsistent, &decl.inputs, |s, arg| s.print_arg(arg, true))?;
-        self.s.word("|")?;
+    crate fn print_fn_block_args(&mut self, decl: &ast::FnDecl) {
+        self.s.word("|");
+        self.commasep(Inconsistent, &decl.inputs, |s, arg| s.print_arg(arg, true));
+        self.s.word("|");
 
         if let ast::FunctionRetTy::Default(..) = decl.output {
-            return Ok(());
+            return;
         }
 
-        self.space_if_not_bol()?;
-        self.word_space("->")?;
+        self.space_if_not_bol();
+        self.word_space("->");
         match decl.output {
             ast::FunctionRetTy::Ty(ref ty) => {
-                self.print_type(ty)?;
+                self.print_type(ty);
                 self.maybe_print_comment(ty.span.lo())
             }
             ast::FunctionRetTy::Default(..) => unreachable!(),
         }
     }
 
-    crate fn print_movability(&mut self, movability: ast::Movability)
-                                -> io::Result<()> {
+    crate fn print_movability(&mut self, movability: ast::Movability) {
         match movability {
             ast::Movability::Static => self.word_space("static"),
-            ast::Movability::Movable => Ok(()),
+            ast::Movability::Movable => {},
         }
     }
 
-    crate fn print_asyncness(&mut self, asyncness: ast::IsAsync)
-                                -> io::Result<()> {
+    crate fn print_asyncness(&mut self, asyncness: ast::IsAsync) {
         if asyncness.is_async() {
-            self.word_nbsp("async")?;
+            self.word_nbsp("async");
         }
-        Ok(())
     }
 
-    crate fn print_capture_clause(&mut self, capture_clause: ast::CaptureBy)
-                                -> io::Result<()> {
+    crate fn print_capture_clause(&mut self, capture_clause: ast::CaptureBy) {
         match capture_clause {
             ast::CaptureBy::Value => self.word_space("move"),
-            ast::CaptureBy::Ref => Ok(()),
+            ast::CaptureBy::Ref => {},
         }
     }
 
-    crate fn print_type_bounds(&mut self, prefix: &'static str, bounds: &[ast::GenericBound])
-                             -> io::Result<()> {
+    crate fn print_type_bounds(&mut self, prefix: &'static str, bounds: &[ast::GenericBound]) {
         if !bounds.is_empty() {
-            self.s.word(prefix)?;
+            self.s.word(prefix);
             let mut first = true;
             for bound in bounds {
                 if !(first && prefix.is_empty()) {
-                    self.nbsp()?;
+                    self.nbsp();
                 }
                 if first {
                     first = false;
                 } else {
-                    self.word_space("+")?;
+                    self.word_space("+");
                 }
 
                 match bound {
                     GenericBound::Trait(tref, modifier) => {
                         if modifier == &TraitBoundModifier::Maybe {
-                            self.s.word("?")?;
+                            self.s.word("?");
                         }
-                        self.print_poly_trait_ref(tref)?;
+                        self.print_poly_trait_ref(tref);
                     }
-                    GenericBound::Outlives(lt) => self.print_lifetime(*lt)?,
+                    GenericBound::Outlives(lt) => self.print_lifetime(*lt),
                 }
             }
         }
-        Ok(())
     }
 
-    crate fn print_lifetime(&mut self, lifetime: ast::Lifetime) -> io::Result<()> {
+    crate fn print_lifetime(&mut self, lifetime: ast::Lifetime) {
         self.print_name(lifetime.ident.name)
     }
 
-    crate fn print_lifetime_bounds(&mut self, lifetime: ast::Lifetime, bounds: &ast::GenericBounds)
-        -> io::Result<()>
-    {
-        self.print_lifetime(lifetime)?;
+    crate fn print_lifetime_bounds(
+        &mut self, lifetime: ast::Lifetime, bounds: &ast::GenericBounds) {
+        self.print_lifetime(lifetime);
         if !bounds.is_empty() {
-            self.s.word(": ")?;
+            self.s.word(": ");
             for (i, bound) in bounds.iter().enumerate() {
                 if i != 0 {
-                    self.s.word(" + ")?;
+                    self.s.word(" + ");
                 }
                 match bound {
-                    ast::GenericBound::Outlives(lt) => self.print_lifetime(*lt)?,
+                    ast::GenericBound::Outlives(lt) => self.print_lifetime(*lt),
                     _ => panic!(),
                 }
             }
         }
-        Ok(())
     }
 
-    crate fn print_generic_params(
-        &mut self,
-        generic_params: &[ast::GenericParam]
-    ) -> io::Result<()> {
+    crate fn print_generic_params(&mut self, generic_params: &[ast::GenericParam]) {
         if generic_params.is_empty() {
-            return Ok(());
+            return;
         }
 
-        self.s.word("<")?;
+        self.s.word("<");
 
         self.commasep(Inconsistent, &generic_params, |s, param| {
             match param.kind {
                 ast::GenericParamKind::Lifetime => {
-                    s.print_outer_attributes_inline(&param.attrs)?;
+                    s.print_outer_attributes_inline(&param.attrs);
                     let lt = ast::Lifetime { id: param.id, ident: param.ident };
                     s.print_lifetime_bounds(lt, &param.bounds)
                 }
                 ast::GenericParamKind::Type { ref default } => {
-                    s.print_outer_attributes_inline(&param.attrs)?;
-                    s.print_ident(param.ident)?;
-                    s.print_type_bounds(":", &param.bounds)?;
+                    s.print_outer_attributes_inline(&param.attrs);
+                    s.print_ident(param.ident);
+                    s.print_type_bounds(":", &param.bounds);
                     match default {
                         Some(ref default) => {
-                            s.s.space()?;
-                            s.word_space("=")?;
+                            s.s.space();
+                            s.word_space("=");
                             s.print_type(default)
                         }
-                        _ => Ok(())
+                        _ => {}
                     }
                 }
                 ast::GenericParamKind::Const { ref ty } => {
-                    s.print_outer_attributes_inline(&param.attrs)?;
-                    s.word_space("const")?;
-                    s.print_ident(param.ident)?;
-                    s.s.space()?;
-                    s.word_space(":")?;
-                    s.print_type(ty)?;
+                    s.print_outer_attributes_inline(&param.attrs);
+                    s.word_space("const");
+                    s.print_ident(param.ident);
+                    s.s.space();
+                    s.word_space(":");
+                    s.print_type(ty);
                     s.print_type_bounds(":", &param.bounds)
                 }
             }
-        })?;
+        });
 
-        self.s.word(">")?;
-        Ok(())
+        self.s.word(">");
     }
 
-    crate fn print_where_clause(&mut self, where_clause: &ast::WhereClause)
-                              -> io::Result<()> {
+    crate fn print_where_clause(&mut self, where_clause: &ast::WhereClause) {
         if where_clause.predicates.is_empty() {
-            return Ok(())
+            return;
         }
 
-        self.s.space()?;
-        self.word_space("where")?;
+        self.s.space();
+        self.word_space("where");
 
         for (i, predicate) in where_clause.predicates.iter().enumerate() {
             if i != 0 {
-                self.word_space(",")?;
+                self.word_space(",");
             }
 
             match *predicate {
@@ -2870,83 +2813,78 @@ impl<'a> State<'a> {
                     ref bounds,
                     ..
                 }) => {
-                    self.print_formal_generic_params(bound_generic_params)?;
-                    self.print_type(bounded_ty)?;
-                    self.print_type_bounds(":", bounds)?;
+                    self.print_formal_generic_params(bound_generic_params);
+                    self.print_type(bounded_ty);
+                    self.print_type_bounds(":", bounds);
                 }
                 ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate{ref lifetime,
                                                                                ref bounds,
                                                                                ..}) => {
-                    self.print_lifetime_bounds(*lifetime, bounds)?;
+                    self.print_lifetime_bounds(*lifetime, bounds);
                 }
                 ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{ref lhs_ty,
                                                                        ref rhs_ty,
                                                                        ..}) => {
-                    self.print_type(lhs_ty)?;
-                    self.s.space()?;
-                    self.word_space("=")?;
-                    self.print_type(rhs_ty)?;
+                    self.print_type(lhs_ty);
+                    self.s.space();
+                    self.word_space("=");
+                    self.print_type(rhs_ty);
                 }
             }
         }
-
-        Ok(())
     }
 
-    crate fn print_use_tree(&mut self, tree: &ast::UseTree) -> io::Result<()> {
+    crate fn print_use_tree(&mut self, tree: &ast::UseTree) {
         match tree.kind {
             ast::UseTreeKind::Simple(rename, ..) => {
-                self.print_path(&tree.prefix, false, 0)?;
+                self.print_path(&tree.prefix, false, 0);
                 if let Some(rename) = rename {
-                    self.s.space()?;
-                    self.word_space("as")?;
-                    self.print_ident(rename)?;
+                    self.s.space();
+                    self.word_space("as");
+                    self.print_ident(rename);
                 }
             }
             ast::UseTreeKind::Glob => {
                 if !tree.prefix.segments.is_empty() {
-                    self.print_path(&tree.prefix, false, 0)?;
-                    self.s.word("::")?;
+                    self.print_path(&tree.prefix, false, 0);
+                    self.s.word("::");
                 }
-                self.s.word("*")?;
+                self.s.word("*");
             }
             ast::UseTreeKind::Nested(ref items) => {
                 if tree.prefix.segments.is_empty() {
-                    self.s.word("{")?;
+                    self.s.word("{");
                 } else {
-                    self.print_path(&tree.prefix, false, 0)?;
-                    self.s.word("::{")?;
+                    self.print_path(&tree.prefix, false, 0);
+                    self.s.word("::{");
                 }
                 self.commasep(Inconsistent, &items[..], |this, &(ref tree, _)| {
                     this.print_use_tree(tree)
-                })?;
-                self.s.word("}")?;
+                });
+                self.s.word("}");
             }
         }
-
-        Ok(())
     }
 
-    crate fn print_mutability(&mut self,
-                            mutbl: ast::Mutability) -> io::Result<()> {
+    crate fn print_mutability(&mut self, mutbl: ast::Mutability) {
         match mutbl {
             ast::Mutability::Mutable => self.word_nbsp("mut"),
-            ast::Mutability::Immutable => Ok(()),
+            ast::Mutability::Immutable => {},
         }
     }
 
-    crate fn print_mt(&mut self, mt: &ast::MutTy) -> io::Result<()> {
-        self.print_mutability(mt.mutbl)?;
+    crate fn print_mt(&mut self, mt: &ast::MutTy) {
+        self.print_mutability(mt.mutbl);
         self.print_type(&mt.ty)
     }
 
-    crate fn print_arg(&mut self, input: &ast::Arg, is_closure: bool) -> io::Result<()> {
-        self.ibox(INDENT_UNIT)?;
+    crate fn print_arg(&mut self, input: &ast::Arg, is_closure: bool) {
+        self.ibox(INDENT_UNIT);
         match input.ty.node {
-            ast::TyKind::Infer if is_closure => self.print_pat(&input.pat)?,
+            ast::TyKind::Infer if is_closure => self.print_pat(&input.pat),
             _ => {
                 if let Some(eself) = input.to_self() {
-                    self.print_explicit_self(&eself)?;
+                    self.print_explicit_self(&eself);
                 } else {
                     let invalid = if let PatKind::Ident(_, ident, _) = input.pat.node {
                         ident.name == kw::Invalid
@@ -2954,35 +2892,35 @@ impl<'a> State<'a> {
                         false
                     };
                     if !invalid {
-                        self.print_pat(&input.pat)?;
-                        self.s.word(":")?;
-                        self.s.space()?;
+                        self.print_pat(&input.pat);
+                        self.s.word(":");
+                        self.s.space();
                     }
-                    self.print_type(&input.ty)?;
+                    self.print_type(&input.ty);
                 }
             }
         }
-        self.end()
+        self.end();
     }
 
-    crate fn print_fn_output(&mut self, decl: &ast::FnDecl) -> io::Result<()> {
+    crate fn print_fn_output(&mut self, decl: &ast::FnDecl) {
         if let ast::FunctionRetTy::Default(..) = decl.output {
-            return Ok(());
+            return;
         }
 
-        self.space_if_not_bol()?;
-        self.ibox(INDENT_UNIT)?;
-        self.word_space("->")?;
+        self.space_if_not_bol();
+        self.ibox(INDENT_UNIT);
+        self.word_space("->");
         match decl.output {
             ast::FunctionRetTy::Default(..) => unreachable!(),
             ast::FunctionRetTy::Ty(ref ty) =>
-                self.print_type(ty)?
+                self.print_type(ty),
         }
-        self.end()?;
+        self.end();
 
         match decl.output {
             ast::FunctionRetTy::Ty(ref output) => self.maybe_print_comment(output.span.lo()),
-            _ => Ok(())
+            _ => {}
         }
     }
 
@@ -2992,11 +2930,11 @@ impl<'a> State<'a> {
                        decl: &ast::FnDecl,
                        name: Option<ast::Ident>,
                        generic_params: &[ast::GenericParam])
-                       -> io::Result<()> {
-        self.ibox(INDENT_UNIT)?;
+                       {
+        self.ibox(INDENT_UNIT);
         if !generic_params.is_empty() {
-            self.s.word("for")?;
-            self.print_generic_params(generic_params)?;
+            self.s.word("for");
+            self.print_generic_params(generic_params);
         }
         let generics = ast::Generics {
             params: Vec::new(),
@@ -3010,73 +2948,71 @@ impl<'a> State<'a> {
                       ast::FnHeader { unsafety, abi, ..ast::FnHeader::default() },
                       name,
                       &generics,
-                      &source_map::dummy_spanned(ast::VisibilityKind::Inherited))?;
-        self.end()
+                      &source_map::dummy_spanned(ast::VisibilityKind::Inherited));
+        self.end();
     }
 
     crate fn maybe_print_trailing_comment(&mut self, span: syntax_pos::Span,
                                         next_pos: Option<BytePos>)
-        -> io::Result<()> {
+        {
         let cm = match self.cm {
             Some(cm) => cm,
-            _ => return Ok(())
+            _ => return,
         };
         if let Some(ref cmnt) = self.next_comment() {
-            if cmnt.style != comments::Trailing { return Ok(()) }
+            if cmnt.style != comments::Trailing { return; }
             let span_line = cm.lookup_char_pos(span.hi());
             let comment_line = cm.lookup_char_pos(cmnt.pos);
             let next = next_pos.unwrap_or_else(|| cmnt.pos + BytePos(1));
             if span.hi() < cmnt.pos && cmnt.pos < next && span_line.line == comment_line.line {
-                self.print_comment(cmnt)?;
+                self.print_comment(cmnt);
             }
         }
-        Ok(())
     }
 
-    crate fn print_remaining_comments(&mut self) -> io::Result<()> {
+    crate fn print_remaining_comments(&mut self) {
         // If there aren't any remaining comments, then we need to manually
         // make sure there is a line break at the end.
         if self.next_comment().is_none() {
-            self.s.hardbreak()?;
+            self.s.hardbreak();
         }
         while let Some(ref cmnt) = self.next_comment() {
-            self.print_comment(cmnt)?;
+            self.print_comment(cmnt);
         }
-        Ok(())
     }
 
     crate fn print_fn_header_info(&mut self,
                                 header: ast::FnHeader,
-                                vis: &ast::Visibility) -> io::Result<()> {
-        self.s.word(visibility_qualified(vis, ""))?;
+                                vis: &ast::Visibility) {
+        self.s.word(visibility_qualified(vis, ""));
 
         match header.constness.node {
             ast::Constness::NotConst => {}
-            ast::Constness::Const => self.word_nbsp("const")?
+            ast::Constness::Const => self.word_nbsp("const")
         }
 
-        self.print_asyncness(header.asyncness.node)?;
-        self.print_unsafety(header.unsafety)?;
+        self.print_asyncness(header.asyncness.node);
+        self.print_unsafety(header.unsafety);
 
         if header.abi != Abi::Rust {
-            self.word_nbsp("extern")?;
-            self.word_nbsp(header.abi.to_string())?;
+            self.word_nbsp("extern");
+            self.word_nbsp(header.abi.to_string());
         }
 
         self.s.word("fn")
     }
 
-    crate fn print_unsafety(&mut self, s: ast::Unsafety) -> io::Result<()> {
+    crate fn print_unsafety(&mut self, s: ast::Unsafety) {
         match s {
-            ast::Unsafety::Normal => Ok(()),
+            ast::Unsafety::Normal => {},
             ast::Unsafety::Unsafe => self.word_nbsp("unsafe"),
         }
     }
 
-    crate fn print_is_auto(&mut self, s: ast::IsAuto) -> io::Result<()> {
+    crate fn print_is_auto(&mut self, s: ast::IsAuto) {
         match s {
             ast::IsAuto::Yes => self.word_nbsp("auto"),
-            ast::IsAuto::No => Ok(()),
+            ast::IsAuto::No => {}
         }
     }
 }