Format paths

1 files changed, 350 insertions, 46 deletions

diff --git a/src/types.rs b/src/types.rs
index c2e27c31684..4917d6ac3c9 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -8,33 +8,311 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use visitor::FmtVisitor;
+use std::fmt;
 
 use syntax::ast;
 use syntax::print::pprust;
+use syntax::codemap::{self, Span, BytePos, CodeMap};
 
-impl<'a> FmtVisitor<'a> {
-    pub fn rewrite_pred(&self, predicate: &ast::WherePredicate) -> String {
-        // TODO dead spans
+use lists::{itemize_list, write_list, ListTactic, SeparatorTactic, ListFormatting};
+use rewrite::{Rewrite, RewriteContext};
+use utils::{extra_offset, span_after};
+
+impl Rewrite for ast::Path {
+    fn rewrite(&self, context: &RewriteContext, width: usize, offset: usize) -> Option<String> {
+        rewrite_path(context, None, self, width, offset)
+    }
+}
+
+// Does not wrap on simple segments.
+pub fn rewrite_path(context: &RewriteContext,
+                    qself: Option<&ast::QSelf>,
+                    path: &ast::Path,
+                    width: usize,
+                    offset: usize)
+                    -> Option<String> {
+    let skip_count = qself.map(|x| x.position).unwrap_or(0);
+
+    let mut result = if path.global {
+        "::".to_owned()
+    } else {
+        String::new()
+    };
+
+    let mut span_lo = path.span.lo;
+
+    if let Some(ref qself) = qself {
+        result.push('<');
+        result.push_str(&pprust::ty_to_string(&qself.ty));
+        result.push_str(" as ");
+
+        let extra_offset = extra_offset(&result, offset);
+        // 3 = ">::".len()
+        let budget = try_opt!(width.checked_sub(extra_offset)) - 3;
+
+        result = try_opt!(rewrite_path_segments(result,
+                                                path.segments.iter().take(skip_count),
+                                                span_lo,
+                                                path.span.hi,
+                                                context,
+                                                budget,
+                                                offset + extra_offset));
+
+        result.push_str(">::");
+        span_lo = qself.ty.span.hi + BytePos(1);
+    }
+
+    let extra_offset = extra_offset(&result, offset);
+    let budget = try_opt!(width.checked_sub(extra_offset));
+    rewrite_path_segments(result,
+                          path.segments.iter().skip(skip_count),
+                          span_lo,
+                          path.span.hi,
+                          context,
+                          budget,
+                          offset + extra_offset)
+}
+
+fn rewrite_path_segments<'a, I>(mut buffer: String,
+                                iter: I,
+                                mut span_lo: BytePos,
+                                span_hi: BytePos,
+                                context: &RewriteContext,
+                                width: usize,
+                                offset: usize)
+                                -> Option<String>
+    where I: Iterator<Item = &'a ast::PathSegment>
+{
+    let mut first = true;
+
+    for segment in iter {
+        let extra_offset = extra_offset(&buffer, offset);
+        let remaining_width = try_opt!(width.checked_sub(extra_offset));
+        let new_offset = offset + extra_offset;
+        let segment_string = try_opt!(rewrite_segment(segment,
+                                                      &mut span_lo,
+                                                      span_hi,
+                                                      context,
+                                                      remaining_width,
+                                                      new_offset));
+
+        if first {
+            first = false;
+        } else {
+            buffer.push_str("::");
+        }
+
+        buffer.push_str(&segment_string);
+    }
+
+    Some(buffer)
+}
+
+enum SegmentParam<'a> {
+    LifeTime(&'a ast::Lifetime),
+    Type(&'a ast::Ty),
+    Binding(&'a ast::TypeBinding),
+}
+
+impl<'a> SegmentParam<'a> {
+    fn get_span(&self) -> Span {
+        match *self {
+            SegmentParam::LifeTime(ref lt) => lt.span,
+            SegmentParam::Type(ref ty) => ty.span,
+            SegmentParam::Binding(ref binding) => binding.span,
+        }
+    }
+}
+
+impl<'a> fmt::Display for SegmentParam<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            SegmentParam::LifeTime(ref lt) => {
+                write!(f, "{}", pprust::lifetime_to_string(lt))
+            }
+            SegmentParam::Type(ref ty) => {
+                write!(f, "{}", pprust::ty_to_string(ty))
+            }
+            SegmentParam::Binding(ref binding) => {
+                write!(f, "{} = {}", binding.ident, pprust::ty_to_string(&*binding.ty))
+            }
+        }
+    }
+}
+
+// This is a dirty hack to determine if we're in an expression or not. Generic
+// parameters are passed differently in expressions and items. We'd declare
+// a struct with Foo<A, B>, but call its functions with Foo::<A, B>::f().
+// We'd really rather not do this, but there doesn't seem to be an alternative
+// at this point.
+// FIXME: fails with spans containing comments with the characters < or :
+fn get_path_separator(codemap: &CodeMap,
+                      path_start: BytePos,
+                      segment_start: BytePos)
+                      -> &'static str {
+    let span = codemap::mk_sp(path_start, segment_start);
+    let snippet = codemap.span_to_snippet(span).unwrap();
+
+    for c in snippet.chars().rev() {
+        if c == ':' {
+            return "::"
+        } else if c.is_whitespace() || c == '<' {
+            continue;
+        } else {
+            return "";
+        }
+    }
+
+    unreachable!();
+}
+
+// Formats a path segment. There are some hacks involved to correctly determine
+// the segment's associated span since it's not part of the AST.
+//
+// The span_lo is assumed to be greater than the end of any previous segment's
+// parameters and lesser or equal than the start of current segment.
+//
+// span_hi is assumed equal to the end of the entire path.
+//
+// When the segment contains a positive number of parameters, we update span_lo
+// so that invariants described above will hold for the next segment.
+fn rewrite_segment(segment: &ast::PathSegment,
+                   span_lo: &mut BytePos,
+                   span_hi: BytePos,
+                   context: &RewriteContext,
+                   width: usize,
+                   offset: usize)
+                   -> Option<String> {
+    let ident_len = segment.identifier.to_string().len();
+    let width = try_opt!(width.checked_sub(ident_len));
+    let offset = offset + ident_len;
+
+    let params = match segment.parameters {
+        ast::PathParameters::AngleBracketedParameters(ref data) if data.lifetimes.len() > 0 ||
+                                                                   data.types.len() > 0 ||
+                                                                   data.bindings.len() > 0 => {
+            let param_list = data.lifetimes.iter()
+                                           .map(SegmentParam::LifeTime)
+                                           .chain(data.types.iter()
+                                                      .map(|x| SegmentParam::Type(&*x)))
+                                           .chain(data.bindings.iter()
+                                                      .map(|x| SegmentParam::Binding(&*x)))
+                                           .collect::<Vec<_>>();
+
+            let next_span_lo = param_list.last().unwrap().get_span().hi + BytePos(1);
+            let list_lo = span_after(codemap::mk_sp(*span_lo, span_hi), "<", context.codemap);
+            let separator = get_path_separator(context.codemap, *span_lo, list_lo);
+
+            let items = itemize_list(context.codemap,
+                                     Vec::new(),
+                                     param_list.into_iter(),
+                                     ",",
+                                     ">",
+                                     |param| param.get_span().lo,
+                                     |param| param.get_span().hi,
+                                     ToString::to_string,
+                                     list_lo,
+                                     span_hi);
+
+            // 1 for <
+            let extra_offset = 1 + separator.len();
+            // 1 for >
+            let list_width = try_opt!(width.checked_sub(extra_offset + 1));
+
+            let fmt = ListFormatting {
+                tactic: ListTactic::HorizontalVertical,
+                separator: ",",
+                trailing_separator: SeparatorTactic::Never,
+                indent: offset + extra_offset,
+                h_width: list_width,
+                v_width: list_width,
+                ends_with_newline: false,
+            };
+
+            // update pos
+            *span_lo = next_span_lo;
+
+            format!("{}<{}>", separator, write_list(&items, &fmt))
+        }
+        ast::PathParameters::ParenthesizedParameters(ref data) => {
+            let output = match data.output {
+                Some(ref ty) => format!(" -> {}", pprust::ty_to_string(&*ty)),
+                None => String::new()
+            };
+
+            let list_lo = span_after(codemap::mk_sp(*span_lo, span_hi), "(", context.codemap);
+            let items = itemize_list(context.codemap,
+                                     Vec::new(),
+                                     data.inputs.iter(),
+                                     ",",
+                                     ")",
+                                     |ty| ty.span.lo,
+                                     |ty| ty.span.hi,
+                                     |ty| pprust::ty_to_string(ty),
+                                     list_lo,
+                                     span_hi);
+
+            // 2 for ()
+            let budget = try_opt!(width.checked_sub(output.len() + 2));
+
+            let fmt = ListFormatting {
+                tactic: ListTactic::HorizontalVertical,
+                separator: ",",
+                trailing_separator: SeparatorTactic::Never,
+                // 1 for (
+                indent: offset + 1,
+                h_width: budget,
+                v_width: budget,
+                ends_with_newline: false,
+            };
+
+            // update pos
+            *span_lo = data.inputs.last().unwrap().span.hi + BytePos(1);
+
+            format!("({}){}", write_list(&items, &fmt), output)
+        }
+        _ => String::new()
+    };
+
+    Some(format!("{}{}", segment.identifier, params))
+}
+
+impl Rewrite for ast::WherePredicate {
+    fn rewrite(&self, context: &RewriteContext, width: usize, offset: usize) -> Option<String> {
+        // TODO dead spans?
         // TODO assumes we'll always fit on one line...
-        match predicate {
+        Some(match self {
             &ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate{ref bound_lifetimes,
                                                                           ref bounded_ty,
                                                                           ref bounds,
                                                                           ..}) => {
                 if bound_lifetimes.len() > 0 {
-                    format!("for<{}> {}: {}",
-                            bound_lifetimes.iter().map(|l| self.rewrite_lifetime_def(l))
-                                .collect::<Vec<_>>().join(", "),
-                            pprust::ty_to_string(bounded_ty),
-                            bounds.iter().map(|b| self.rewrite_ty_bound(b))
-                                .collect::<Vec<_>>().join(" + "))
+                    let lifetime_str = bound_lifetimes.iter().map(|lt| {
+                                           lt.rewrite(context, width, offset).unwrap()
+                                       }).collect::<Vec<_>>().join(", ");
+                    let type_str = pprust::ty_to_string(bounded_ty);
+                    // 8 = "for<> : ".len()
+                    let used_width = lifetime_str.len() + type_str.len() + 8;
+                    let bounds_str = bounds.iter().map(|ty_bound| {
+                                         ty_bound.rewrite(context,
+                                                          width - used_width,
+                                                          offset + used_width)
+                                                 .unwrap()
+                                     }).collect::<Vec<_>>().join(" + ");
 
+                    format!("for<{}> {}: {}", lifetime_str, type_str, bounds_str)
                 } else {
-                    format!("{}: {}",
-                            pprust::ty_to_string(bounded_ty),
-                            bounds.iter().map(|b| self.rewrite_ty_bound(b))
-                                .collect::<Vec<_>>().join(" + "))
+                    let type_str = pprust::ty_to_string(bounded_ty);
+                    // 2 = ": ".len()
+                    let used_width = type_str.len() + 2;
+                    let bounds_str = bounds.iter().map(|ty_bound| {
+                                         ty_bound.rewrite(context,
+                                                          width - used_width,
+                                                          offset + used_width)
+                                                 .unwrap()
+                                     }).collect::<Vec<_>>().join(" + ");
+
+                    format!("{}: {}", type_str, bounds_str)
                 }
             }
             &ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate{ref lifetime,
@@ -42,65 +320,91 @@ impl<'a> FmtVisitor<'a> {
                                                                             ..}) => {
                 format!("{}: {}",
                         pprust::lifetime_to_string(lifetime),
-                        bounds.iter().map(|l| pprust::lifetime_to_string(l))
-                            .collect::<Vec<_>>().join(" + "))
+                        bounds.iter().map(pprust::lifetime_to_string)
+                              .collect::<Vec<_>>().join(" + "))
             }
             &ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{ref path, ref ty, ..}) => {
-                format!("{} = {}", pprust::path_to_string(path), pprust::ty_to_string(ty))
+                let ty_str = pprust::ty_to_string(ty);
+                // 3 = " = ".len()
+                let used_width = 3 + ty_str.len();
+                let path_str = try_opt!(path.rewrite(context,
+                                                     width - used_width,
+                                                     offset + used_width));
+                format!("{} = {}", path_str, ty_str)
             }
-        }
+        })
     }
+}
 
-    pub fn rewrite_lifetime_def(&self, lifetime: &ast::LifetimeDef) -> String {
-        if lifetime.bounds.len() == 0 {
-            return pprust::lifetime_to_string(&lifetime.lifetime);
+impl Rewrite for ast::LifetimeDef {
+    fn rewrite(&self, _: &RewriteContext, _: usize, _: usize) -> Option<String> {
+        if self.bounds.len() == 0 {
+            Some(pprust::lifetime_to_string(&self.lifetime))
+        } else {
+            Some(format!("{}: {}",
+                         pprust::lifetime_to_string(&self.lifetime),
+                         self.bounds.iter().map(pprust::lifetime_to_string)
+                                    .collect::<Vec<_>>().join(" + ")))
         }
-
-        format!("{}: {}",
-                pprust::lifetime_to_string(&lifetime.lifetime),
-                lifetime.bounds.iter().map(|l| pprust::lifetime_to_string(l))
-                    .collect::<Vec<_>>().join(" + "))
     }
+}
 
-    pub fn rewrite_ty_bound(&self, bound: &ast::TyParamBound) -> String {
-        match *bound {
+impl Rewrite for ast::TyParamBound {
+    fn rewrite(&self, context: &RewriteContext, width: usize, offset: usize) -> Option<String> {
+        match *self {
             ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::None) => {
-                self.rewrite_poly_trait_ref(tref)
+                tref.rewrite(context, width, offset)
             }
             ast::TyParamBound::TraitTyParamBound(ref tref, ast::TraitBoundModifier::Maybe) => {
-                format!("?{}", self.rewrite_poly_trait_ref(tref))
+                Some(format!("?{}", try_opt!(tref.rewrite(context, width - 1, offset + 1))))
             }
             ast::TyParamBound::RegionTyParamBound(ref l) => {
-                pprust::lifetime_to_string(l)
+                Some(pprust::lifetime_to_string(l))
             }
         }
     }
+}
 
-    pub fn rewrite_ty_param(&self, ty_param: &ast::TyParam) -> String {
+// FIXME: this assumes everything will fit on one line
+impl Rewrite for ast::TyParam {
+    fn rewrite(&self, context: &RewriteContext, width: usize, offset: usize) -> Option<String> {
         let mut result = String::with_capacity(128);
-        result.push_str(&ty_param.ident.to_string());
-        if ty_param.bounds.len() > 0 {
+        result.push_str(&self.ident.to_string());
+        if self.bounds.len() > 0 {
             result.push_str(": ");
-            result.push_str(&ty_param.bounds.iter().map(|b| self.rewrite_ty_bound(b))
-                                .collect::<Vec<_>>().join(" + "));
+
+            let bounds = self.bounds.iter().map(|ty_bound| {
+                ty_bound.rewrite(context, width, offset).unwrap()
+            }).collect::<Vec<_>>().join(" + ");
+
+            result.push_str(&bounds);
         }
-        if let Some(ref def) = ty_param.default {
+        if let Some(ref def) = self.default {
             result.push_str(" = ");
             result.push_str(&pprust::ty_to_string(&def));
         }
 
-        result
+        Some(result)
     }
+}
 
-    fn rewrite_poly_trait_ref(&self, t: &ast::PolyTraitRef) -> String {
-        if t.bound_lifetimes.len() > 0 {
-            format!("for<{}> {}",
-                    t.bound_lifetimes.iter().map(|l| self.rewrite_lifetime_def(l))
-                        .collect::<Vec<_>>().join(", "),
-                    pprust::path_to_string(&t.trait_ref.path))
+// FIXME: this assumes everything will fit on one line
+impl Rewrite for ast::PolyTraitRef {
+    fn rewrite(&self, context: &RewriteContext, width: usize, offset: usize) -> Option<String> {
+        if self.bound_lifetimes.len() > 0 {
+            let lifetime_str = self.bound_lifetimes.iter().map(|lt| {
+                lt.rewrite(context, width, offset).unwrap()
+            }).collect::<Vec<_>>().join(", ");
+            // 6 is "for<> ".len()
+            let extra_offset = lifetime_str.len() + 6;
+            let max_path_width = try_opt!(width.checked_sub(extra_offset));
+            let path_str = try_opt!(self.trait_ref.path.rewrite(context,
+                                                                max_path_width,
+                                                                offset + extra_offset));
 
+            Some(format!("for<{}> {}", lifetime_str, path_str))
         } else {
-            pprust::path_to_string(&t.trait_ref.path)
+            self.trait_ref.path.rewrite(context, width, offset)
         }
     }
 }