parse: refactor fun ret ty & param ty

4 files changed, 27 insertions, 13 deletions

diff --git a/src/librustc_parse/parser/expr.rs b/src/librustc_parse/parser/expr.rs
index 3cd4988ce0b..e4dff07e92c 100644
--- a/src/librustc_parse/parser/expr.rs
+++ b/src/librustc_parse/parser/expr.rs
@@ -1381,7 +1381,7 @@ impl<'a> Parser<'a> {
                 args
             }
         };
-        let output = self.parse_ret_ty(true)?;
+        let output = self.parse_ret_ty(true, true)?;
 
         Ok(P(FnDecl {
             inputs: inputs_captures,
diff --git a/src/librustc_parse/parser/item.rs b/src/librustc_parse/parser/item.rs
index dbc0163eef6..f391eda976c 100644
--- a/src/librustc_parse/parser/item.rs
+++ b/src/librustc_parse/parser/item.rs
@@ -1900,7 +1900,7 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, P<FnDecl>> {
         Ok(P(FnDecl {
             inputs: self.parse_fn_params(cfg)?,
-            output: self.parse_ret_ty(ret_allow_plus)?,
+            output: self.parse_ret_ty(ret_allow_plus, true)?,
         }))
     }
 
@@ -2002,12 +2002,12 @@ impl<'a> Parser<'a> {
             }
 
             self.eat_incorrect_doc_comment_for_param_type();
-            (pat, self.parse_ty_common(true, true, cfg.allow_c_variadic)?)
+            (pat, self.parse_ty_for_param(cfg.allow_c_variadic)?)
         } else {
             debug!("parse_param_general ident_to_pat");
             let parser_snapshot_before_ty = self.clone();
             self.eat_incorrect_doc_comment_for_param_type();
-            let mut ty = self.parse_ty_common(true, true, cfg.allow_c_variadic);
+            let mut ty = self.parse_ty_for_param(cfg.allow_c_variadic);
             if ty.is_ok() && self.token != token::Comma &&
                self.token != token::CloseDelim(token::Paren) {
                 // This wasn't actually a type, but a pattern looking like a type,
diff --git a/src/librustc_parse/parser/path.rs b/src/librustc_parse/parser/path.rs
index 5334fc485e7..aeba6dd2f67 100644
--- a/src/librustc_parse/parser/path.rs
+++ b/src/librustc_parse/parser/path.rs
@@ -182,11 +182,7 @@ impl<'a> Parser<'a> {
                 // `(T, U) -> R`
                 let (inputs, _) = self.parse_paren_comma_seq(|p| p.parse_ty())?;
                 let span = ident.span.to(self.prev_span);
-                let output = if self.eat(&token::RArrow) {
-                    Some(self.parse_ty_common(false, false, false)?)
-                } else {
-                    None
-                };
+                let output = self.parse_ret_ty(false, false)?;
                 ParenthesizedArgs { inputs, output, span }.into()
             };
 
diff --git a/src/librustc_parse/parser/ty.rs b/src/librustc_parse/parser/ty.rs
index 33d7c878e88..1dffa6c94a8 100644
--- a/src/librustc_parse/parser/ty.rs
+++ b/src/librustc_parse/parser/ty.rs
@@ -30,6 +30,13 @@ impl<'a> Parser<'a> {
         self.parse_ty_common(true, true, false)
     }
 
+    /// Parse a type suitable for a function or function pointer parameter.
+    /// The difference from `parse_ty` is that this version allows `...`
+    /// (`CVarArgs`) at the top level of the the type.
+    pub(super) fn parse_ty_for_param(&mut self, allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
+        self.parse_ty_common(true, true, allow_c_variadic)
+    }
+
     /// Parses a type in restricted contexts where `+` is not permitted.
     ///
     /// Example 1: `&'a TYPE`
@@ -41,17 +48,26 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses an optional return type `[ -> TY ]` in a function declaration.
-    pub(super) fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
+    pub(super) fn parse_ret_ty(
+        &mut self,
+        allow_plus: bool,
+        allow_qpath_recovery: bool,
+    ) -> PResult<'a, FunctionRetTy> {
         Ok(if self.eat(&token::RArrow) {
             // FIXME(Centril): Can we unconditionally `allow_plus`?
-            FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?)
+            FunctionRetTy::Ty(self.parse_ty_common(allow_plus, allow_qpath_recovery, false)?)
         } else {
             FunctionRetTy::Default(self.token.span.shrink_to_lo())
         })
     }
 
-    pub(super) fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
-                       allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
+    fn parse_ty_common(
+        &mut self,
+        allow_plus: bool,
+        allow_qpath_recovery: bool,
+        // Is `...` (`CVarArgs`) legal in the immediate top level call?
+        allow_c_variadic: bool,
+    ) -> PResult<'a, P<Ty>> {
         maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
         maybe_whole!(self, NtTy, |x| x);
 
@@ -198,6 +214,8 @@ impl<'a> Parser<'a> {
                 self.eat(&token::DotDotDot);
                 TyKind::CVarArgs
             } else {
+                // FIXME(Centril): Should we just allow `...` syntactically
+                // anywhere in a type and use semantic restrictions instead?
                 return Err(struct_span_fatal!(
                     self.sess.span_diagnostic,
                     self.token.span,