Move pp::Printer out field to owned String

This enforces that eof() must be called to get the String out, and
generally is better from an API perspective. No users of pretty printing
pre-allocate the buffer.

2 files changed, 21 insertions, 26 deletions

diff --git a/src/libsyntax/print/pp.rs b/src/libsyntax/print/pp.rs
index f64e95aee5b..ea90defcd50 100644
--- a/src/libsyntax/print/pp.rs
+++ b/src/libsyntax/print/pp.rs
@@ -235,13 +235,13 @@ crate struct PrintStackElem {
 
 const SIZE_INFINITY: isize = 0xffff;
 
-pub fn mk_printer(out: &mut String) -> Printer<'_> {
+pub fn mk_printer() -> Printer {
     let linewidth = 78;
     // Yes 55, it makes the ring buffers big enough to never fall behind.
     let n: usize = 55 * linewidth;
     debug!("mk_printer {}", linewidth);
     Printer {
-        out,
+        out: String::new(),
         buf_max_len: n,
         margin: linewidth as isize,
         space: linewidth as isize,
@@ -258,8 +258,8 @@ pub fn mk_printer(out: &mut String) -> Printer<'_> {
     }
 }
 
-pub struct Printer<'a> {
-    out: &'a mut String,
+pub struct Printer {
+    out: String,
     buf_max_len: usize,
     /// Width of lines we're constrained to
     margin: isize,
@@ -300,7 +300,7 @@ impl Default for BufEntry {
     }
 }
 
-impl<'a> Printer<'a> {
+impl Printer {
     pub fn last_token(&mut self) -> Token {
         self.buf[self.right].token.clone()
     }
@@ -629,8 +629,9 @@ impl<'a> Printer<'a> {
         self.pretty_print_end()
     }
 
-    pub fn eof(&mut self) {
-        self.pretty_print_eof()
+    pub fn eof(mut self) -> String {
+        self.pretty_print_eof();
+        self.out
     }
 
     pub fn word<S: Into<Cow<'static, str>>>(&mut self, wrd: S) {
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 43714d3015b..54672d9da2e 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -87,7 +87,7 @@ impl<'a> Comments<'a> {
 }
 
 pub struct State<'a> {
-    pub s: pp::Printer<'a>,
+    pub s: pp::Printer,
     comments: Option<Comments<'a>>,
     ann: &'a (dyn PpAnn+'a),
     is_expanded: bool
@@ -104,9 +104,8 @@ pub fn print_crate<'a>(cm: &'a SourceMap,
                        input: String,
                        ann: &'a dyn PpAnn,
                        is_expanded: bool) -> String {
-    let mut out = String::new();
     let mut s = State {
-        s: pp::mk_printer(&mut out),
+        s: pp::mk_printer(),
         comments: Some(Comments::new(cm, sess, filename, input)),
         ann,
         is_expanded,
@@ -133,25 +132,20 @@ pub fn print_crate<'a>(cm: &'a SourceMap,
 
     s.print_mod(&krate.module, &krate.attrs);
     s.print_remaining_comments();
-    s.s.eof();
-    out
+    s.s.eof()
 }
 
 pub fn to_string<F>(f: F) -> String where
     F: FnOnce(&mut State<'_>),
 {
-    let mut wr = String::new();
-    {
-        let mut printer = State {
-            s: pp::mk_printer(&mut wr),
-            comments: None,
-            ann: &NoAnn,
-            is_expanded: false
-        };
-        f(&mut printer);
-        printer.s.eof();
-    }
-    wr
+    let mut printer = State {
+        s: pp::mk_printer(),
+        comments: None,
+        ann: &NoAnn,
+        is_expanded: false
+    };
+    f(&mut printer);
+    printer.s.eof()
 }
 
 fn binop_to_string(op: BinOpToken) -> &'static str {
@@ -439,7 +433,7 @@ fn visibility_qualified(vis: &ast::Visibility, s: &str) -> String {
 }
 
 pub trait PrintState<'a> {
-    fn writer(&mut self) -> &mut pp::Printer<'a>;
+    fn writer(&mut self) -> &mut pp::Printer;
     fn comments(&mut self) -> &mut Option<Comments<'a>>;
 
     fn word_space<S: Into<Cow<'static, str>>>(&mut self, w: S) {
@@ -760,7 +754,7 @@ pub trait PrintState<'a> {
 }
 
 impl<'a> PrintState<'a> for State<'a> {
-    fn writer(&mut self) -> &mut pp::Printer<'a> {
+    fn writer(&mut self) -> &mut pp::Printer {
         &mut self.s
     }