[clang] Diagnose shadowing of lambda's template parameter by a capture

expr.prim.lambda.capture p5 says:
If an identifier in a capture appears as the declarator-id of a parameter of
the lambda-declarator's parameter-declaration-clause or as the name of a
template parameter of the lambda-expression's template-parameter-list,
the program is ill-formed.
and also has the following example:
```
auto h = [y = 0]<typename y>(y) { return 0; };
```
which now results in
```
error: declaration of 'y' shadows template parameter
  auto l1 = [y = 0]<typename y>(y) { return 0; };
             ^
note: template parameter is declared here
  auto l1 = [y = 0]<typename y>(y) { return 0; };
                             ^
```

Fixes https://github.com/llvm/llvm-project/issues/61105

Reviewed By: shafik, cor3ntin

Differential Revision: https://reviews.llvm.org/D148712

1 files changed, 2 insertions, 0 deletions

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 8082e9d9f323..a61e6615b937 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -233,6 +233,8 @@ Improvements to Clang's diagnostics
 - ``-Wformat`` now recognizes ``%lb`` for the ``printf``/``scanf`` family of
   functions.
   (`#62247: <https://github.com/llvm/llvm-project/issues/62247>`_).
+- Clang now diagnoses shadowing of lambda's template parameter by a capture.
+  (`#61105: <https://github.com/llvm/llvm-project/issues/61105>`_).
 
 Bug Fixes in This Version
 -------------------------