Prohibit type parameter shadowing with a clunky hammer.

This is a [breaking-change].

Change

    impl<T> Foo<T> {
        fn bar<T>(...

to (for example)

    impl<T> Foo<T> {
        fn bar<U>(...

Per RFC 459.

Closes #19390.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libserialize/json.rs b/src/libserialize/json.rs
index b7bf40a6ec5..d77540b9dde 100644
--- a/src/libserialize/json.rs
+++ b/src/libserialize/json.rs
@@ -1396,7 +1396,7 @@ impl<T: Iterator<Item=char>> Parser<T> {
         self.ch == Some(c)
     }
 
-    fn error<T>(&self, reason: ErrorCode) -> Result<T, ParserError> {
+    fn error<U>(&self, reason: ErrorCode) -> Result<U, ParserError> {
         Err(SyntaxError(reason, self.line, self.col))
     }