From f5db4114102861acd004c8104dde7372010b156e Mon Sep 17 00:00:00 2001
From: Andy Russell <arussell123@gmail.com>
Date: Wed, 3 Oct 2018 22:21:05 -0400
Subject: add suggestion for inverted function parameters

Fixes #54065.
---
 src/libsyntax/parse/parser.rs | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

(limited to 'src/libsyntax')

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 5571a18b596..1825ee6eab8 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -1777,7 +1777,26 @@ impl<'a> Parser<'a> {
                    require_name);
             let pat = self.parse_pat()?;
 
-            self.expect(&token::Colon)?;
+            if let Err(mut err) = self.expect(&token::Colon) {
+                // If we find a pattern followed by an identifier, it could be an (incorrect)
+                // C-style parameter declaration.
+                if self.check_ident() && self.look_ahead(1, |t| {
+                    *t == token::Comma || *t == token::CloseDelim(token::Paren)
+                }) {
+                    let ident = self.parse_ident().unwrap();
+                    let span = pat.span.with_hi(ident.span.hi());
+
+                    err.span_suggestion_with_applicability(
+                        span,
+                        "declare the type after the parameter binding",
+                        String::from("<identifier>: <type>"),
+                        Applicability::HasPlaceholders,
+                    );
+                }
+
+                return Err(err);
+            }
+
             (pat, self.parse_ty()?)
         } else {
             debug!("parse_arg_general ident_to_pat");
-- 
cgit 1.4.1-3-g733a5