From 3bbfc7320ba0f23541f94a84cf5281a210a546cd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Mon, 4 Nov 2019 16:19:55 -0800
Subject: [PATCH] Detect `::` -> `:` typo when involving turbofish

---
 src/libsyntax/parse/parser/diagnostics.rs           |  3 ++-
 src/libsyntax/parse/parser/stmt.rs                  |  1 +
 .../type-ascription-instead-of-path-2.rs            |  5 +++++
 .../type-ascription-instead-of-path-2.stderr        | 13 +++++++++++++
 4 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 src/test/ui/suggestions/type-ascription-instead-of-path-2.rs
 create mode 100644 src/test/ui/suggestions/type-ascription-instead-of-path-2.stderr

diff --git a/src/libsyntax/parse/parser/diagnostics.rs b/src/libsyntax/parse/parser/diagnostics.rs
index ab2b4519cb7..ad479e6278b 100644
--- a/src/libsyntax/parse/parser/diagnostics.rs
+++ b/src/libsyntax/parse/parser/diagnostics.rs
@@ -354,7 +354,7 @@ impl<'a> Parser<'a> {
     }
 
     pub fn maybe_annotate_with_ascription(
-        &self,
+        &mut self,
         err: &mut DiagnosticBuilder<'_>,
         maybe_expected_semicolon: bool,
     ) {
@@ -395,6 +395,7 @@ impl<'a> Parser<'a> {
                 err.note("for more information, see \
                           https://github.com/rust-lang/rust/issues/23416");
             }
+            self.last_type_ascription = None;
         }
     }
 
diff --git a/src/libsyntax/parse/parser/stmt.rs b/src/libsyntax/parse/parser/stmt.rs
index 4f51fefe66f..12c530f3cbb 100644
--- a/src/libsyntax/parse/parser/stmt.rs
+++ b/src/libsyntax/parse/parser/stmt.rs
@@ -397,6 +397,7 @@ impl<'a> Parser<'a> {
             }
             let stmt = match self.parse_full_stmt(false) {
                 Err(mut err) => {
+                    self.maybe_annotate_with_ascription(&mut err, false);
                     err.emit();
                     self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
                     Some(Stmt {
diff --git a/src/test/ui/suggestions/type-ascription-instead-of-path-2.rs b/src/test/ui/suggestions/type-ascription-instead-of-path-2.rs
new file mode 100644
index 00000000000..220fd1eebda
--- /dev/null
+++ b/src/test/ui/suggestions/type-ascription-instead-of-path-2.rs
@@ -0,0 +1,5 @@
+fn main() -> Result<(), ()> {
+    vec![Ok(2)].into_iter().collect:<Result<Vec<_>,_>>()?;
+    //~^ ERROR expected `::`, found `(`
+    Ok(())
+}
diff --git a/src/test/ui/suggestions/type-ascription-instead-of-path-2.stderr b/src/test/ui/suggestions/type-ascription-instead-of-path-2.stderr
new file mode 100644
index 00000000000..191c4f631c4
--- /dev/null
+++ b/src/test/ui/suggestions/type-ascription-instead-of-path-2.stderr
@@ -0,0 +1,13 @@
+error: expected `::`, found `(`
+  --> $DIR/type-ascription-instead-of-path-2.rs:2:55
+   |
+LL |     vec![Ok(2)].into_iter().collect:<Result<Vec<_>,_>>()?;
+   |                                    -                  ^ expected `::`
+   |                                    |
+   |                                    tried to parse a type due to this type ascription
+   |
+   = note: `#![feature(type_ascription)]` lets you annotate an expression with a type: `<expr>: <type>`
+   = note: for more information, see https://github.com/rust-lang/rust/issues/23416
+
+error: aborting due to previous error
+