Auto merge of #21099 - sanxiyn:opt-return-ty, r=alexcrichton

This avoids having ast::Ty nodes which have no counterpart in the source.

6 files changed, 27 insertions, 63 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 0ea429116b0..fcf80410da2 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -1390,6 +1390,10 @@ pub enum FunctionRetTy {
     /// Functions with return type ! that always
     /// raise an error or exit (i.e. never return to the caller)
     NoReturn(Span),
+    /// Return type is not specified. Functions default to () and
+    /// closures default to inference. Span points to where return
+    /// type would be inserted.
+    DefaultReturn(Span),
     /// Everything else
     Return(P<Ty>),
 }
@@ -1398,6 +1402,7 @@ impl FunctionRetTy {
     pub fn span(&self) -> Span {
         match *self {
             NoReturn(span) => span,
+            DefaultReturn(span) => span,
             Return(ref ty) => ty.span
         }
     }
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index 16c29c9b5eb..f484650ad5b 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -726,6 +726,7 @@ pub fn noop_fold_fn_decl<T: Folder>(decl: P<FnDecl>, fld: &mut T) -> P<FnDecl> {
         inputs: inputs.move_map(|x| fld.fold_arg(x)),
         output: match output {
             Return(ty) => Return(fld.fold_ty(ty)),
+            DefaultReturn(span) => DefaultReturn(span),
             NoReturn(span) => NoReturn(span)
         },
         variadic: variadic
@@ -1189,14 +1190,7 @@ pub fn noop_fold_foreign_item<T: Folder>(ni: P<ForeignItem>, folder: &mut T) ->
         attrs: attrs.move_map(|x| folder.fold_attribute(x)),
         node: match node {
             ForeignItemFn(fdec, generics) => {
-                ForeignItemFn(fdec.map(|FnDecl {inputs, output, variadic}| FnDecl {
-                    inputs: inputs.move_map(|a| folder.fold_arg(a)),
-                    output: match output {
-                        Return(ty) => Return(folder.fold_ty(ty)),
-                        NoReturn(span) => NoReturn(span)
-                    },
-                    variadic: variadic
-                }), folder.fold_generics(generics))
+                ForeignItemFn(folder.fold_fn_decl(fdec), folder.fold_generics(generics))
             }
             ForeignItemStatic(t, m) => {
                 ForeignItemStatic(folder.fold_ty(t), m)
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index f1f547ba0c7..90e236dfde3 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -1066,9 +1066,7 @@ mod test {
                                     }),
                                         id: ast::DUMMY_NODE_ID
                                     }),
-                                output: ast::Return(P(ast::Ty{id: ast::DUMMY_NODE_ID,
-                                                  node: ast::TyTup(vec![]),
-                                                  span:sp(15,15)})), // not sure
+                                output: ast::DefaultReturn(sp(15, 15)),
                                 variadic: false
                             }),
                                     ast::Unsafety::Normal,
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 130972b4582..b2f6938f513 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -19,7 +19,8 @@ use ast::{Mod, BiAdd, Arg, Arm, Attribute, BindByRef, BindByValue};
 use ast::{BiBitAnd, BiBitOr, BiBitXor, BiRem, BiLt, BiGt, Block};
 use ast::{BlockCheckMode, CaptureByRef, CaptureByValue, CaptureClause};
 use ast::{Crate, CrateConfig, Decl, DeclItem};
-use ast::{DeclLocal, DefaultBlock, UnDeref, BiDiv, EMPTY_CTXT, EnumDef, ExplicitSelf};
+use ast::{DeclLocal, DefaultBlock, DefaultReturn};
+use ast::{UnDeref, BiDiv, EMPTY_CTXT, EnumDef, ExplicitSelf};
 use ast::{Expr, Expr_, ExprAddrOf, ExprMatch, ExprAgain};
 use ast::{ExprAssign, ExprAssignOp, ExprBinary, ExprBlock, ExprBox};
 use ast::{ExprBreak, ExprCall, ExprCast};
@@ -1426,11 +1427,7 @@ impl<'a> Parser<'a> {
             }
         } else {
             let pos = self.span.lo;
-            Return(P(Ty {
-                id: ast::DUMMY_NODE_ID,
-                node: TyTup(vec![]),
-                span: mk_sp(pos, pos),
-            }))
+            DefaultReturn(mk_sp(pos, pos))
         }
     }
 
@@ -4550,15 +4547,7 @@ impl<'a> Parser<'a> {
                 (optional_unboxed_closure_kind, args)
             }
         };
-        let output = if self.check(&token::RArrow) {
-            self.parse_ret_ty()
-        } else {
-            Return(P(Ty {
-                id: ast::DUMMY_NODE_ID,
-                node: TyInfer,
-                span: self.span,
-            }))
-        };
+        let output = self.parse_ret_ty();
 
         (P(FnDecl {
             inputs: inputs_captures,
@@ -4575,15 +4564,7 @@ impl<'a> Parser<'a> {
                                      seq_sep_trailing_allowed(token::Comma),
                                      |p| p.parse_fn_block_arg());
 
-        let output = if self.check(&token::RArrow) {
-            self.parse_ret_ty()
-        } else {
-            Return(P(Ty {
-                id: ast::DUMMY_NODE_ID,
-                node: TyInfer,
-                span: self.span,
-            }))
-        };
+        let output = self.parse_ret_ty();
 
         P(FnDecl {
             inputs: inputs,
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 5d76dc71006..b59e770c6ba 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -2351,10 +2351,8 @@ impl<'a> State<'a> {
         try!(self.print_fn_args(decl, None));
         try!(word(&mut self.s, "|"));
 
-        if let ast::Return(ref ty) = decl.output {
-            if ty.node == ast::TyInfer {
-                return self.maybe_print_comment(ty.span.lo);
-            }
+        if let ast::DefaultReturn(..) = decl.output {
+            return Ok(());
         }
 
         try!(self.space_if_not_bol());
@@ -2364,6 +2362,7 @@ impl<'a> State<'a> {
                 try!(self.print_type(&**ty));
                 self.maybe_print_comment(ty.span.lo)
             }
+            ast::DefaultReturn(..) => unreachable!(),
             ast::NoReturn(span) => {
                 try!(self.word_nbsp("!"));
                 self.maybe_print_comment(span.lo)
@@ -2385,10 +2384,8 @@ impl<'a> State<'a> {
         try!(self.print_fn_args(decl, None));
         try!(word(&mut self.s, ")"));
 
-        if let ast::Return(ref ty) = decl.output {
-            if ty.node == ast::TyInfer {
-                return self.maybe_print_comment(ty.span.lo);
-            }
+        if let ast::DefaultReturn(..) = decl.output {
+            return Ok(());
         }
 
         try!(self.space_if_not_bol());
@@ -2398,6 +2395,7 @@ impl<'a> State<'a> {
                 try!(self.print_type(&**ty));
                 self.maybe_print_comment(ty.span.lo)
             }
+            ast::DefaultReturn(..) => unreachable!(),
             ast::NoReturn(span) => {
                 try!(self.word_nbsp("!"));
                 self.maybe_print_comment(span.lo)
@@ -2684,13 +2682,8 @@ impl<'a> State<'a> {
     }
 
     pub fn print_fn_output(&mut self, decl: &ast::FnDecl) -> IoResult<()> {
-        if let ast::Return(ref ty) = decl.output {
-            match ty.node {
-                ast::TyTup(ref tys) if tys.is_empty() => {
-                    return self.maybe_print_comment(ty.span.lo);
-                }
-                _ => ()
-            }
+        if let ast::DefaultReturn(..) = decl.output {
+            return Ok(());
         }
 
         try!(self.space_if_not_bol());
@@ -2699,6 +2692,7 @@ impl<'a> State<'a> {
         match decl.output {
             ast::NoReturn(_) =>
                 try!(self.word_nbsp("!")),
+            ast::DefaultReturn(..) => unreachable!(),
             ast::Return(ref ty) =>
                 try!(self.print_type(&**ty))
         }
@@ -3071,9 +3065,7 @@ mod test {
 
         let decl = ast::FnDecl {
             inputs: Vec::new(),
-            output: ast::Return(P(ast::Ty {id: 0,
-                               node: ast::TyTup(vec![]),
-                               span: codemap::DUMMY_SP})),
+            output: ast::DefaultReturn(codemap::DUMMY_SP),
             variadic: false
         };
         let generics = ast_util::empty_generics();
diff --git a/src/libsyntax/test.rs b/src/libsyntax/test.rs
index 895268f96c8..5f869d5093f 100644
--- a/src/libsyntax/test.rs
+++ b/src/libsyntax/test.rs
@@ -297,11 +297,8 @@ fn is_test_fn(cx: &TestCtxt, i: &ast::Item) -> bool {
         match &i.node {
           &ast::ItemFn(ref decl, _, _, ref generics, _) => {
             let no_output = match decl.output {
-                ast::Return(ref ret_ty) => match ret_ty.node {
-                    ast::TyTup(ref tys) if tys.is_empty() => true,
-                    _ => false,
-                },
-                ast::NoReturn(_) => false
+                ast::DefaultReturn(..) => true,
+                _ => false
             };
             if decl.inputs.is_empty()
                    && no_output
@@ -336,11 +333,8 @@ fn is_bench_fn(cx: &TestCtxt, i: &ast::Item) -> bool {
             ast::ItemFn(ref decl, _, _, ref generics, _) => {
                 let input_cnt = decl.inputs.len();
                 let no_output = match decl.output {
-                    ast::Return(ref ret_ty) => match ret_ty.node {
-                        ast::TyTup(ref tys) if tys.is_empty() => true,
-                        _ => false,
-                    },
-                    ast::NoReturn(_) => false
+                    ast::DefaultReturn(..) => true,
+                    _ => false
                 };
                 let tparm_cnt = generics.ty_params.len();
                 // NB: inadequate check, but we're running