https://github.com/cor3ntin created
https://github.com/llvm/llvm-project/pull/107073
We only check that a default argument is a converted constant expression when
using the default argument.
However, when parsing a default argument, we need to make sure to parse it as a
constant expression such as not ODR-use variables. (otherwise, we would try to
capture default template arguments of generic lambdas)
Fixes #107048
>From 5edd9a9abe019af2a14ccf9fbf43858f4141071b Mon Sep 17 00:00:00 2001
From: Corentin Jabot <corentinja...@gmail.com>
Date: Tue, 3 Sep 2024 11:25:27 +0200
Subject: [PATCH] [Clang] Treat default template argument as constant
expressions
We only check that a default argument is a converted constant
expression when using the default argument.
However, when parsing a default argument, we need to make sure
to parse it as a constant expression such as not ODR-use variables.
(otherwise, we would try to capture default template arguments
of generic lambdas)
Fixes #107048
---
clang/docs/ReleaseNotes.rst | 1 +
clang/lib/Parse/ParseTemplate.cpp | 2 ++
clang/test/SemaCXX/cxx2a-template-lambdas.cpp | 19 +++++++++++++++++++
3 files changed, 22 insertions(+)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index fc940db4813948..e15414b994a36b 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -339,6 +339,7 @@ Bug Fixes to C++ Support
- Template parameter names are considered in the name lookup of out-of-line
class template
specialization right before its declaration context. (#GH64082)
- Fixed a constraint comparison bug for friend declarations. (#GH78101)
+- Clang no longer tries to capture default argument of template arguments of
generic lambdas (#GH107048)
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Parse/ParseTemplate.cpp
b/clang/lib/Parse/ParseTemplate.cpp
index 6ecfc15757f3d4..b80999f1b92e7f 100644
--- a/clang/lib/Parse/ParseTemplate.cpp
+++ b/clang/lib/Parse/ParseTemplate.cpp
@@ -960,6 +960,8 @@ Parser::ParseNonTypeTemplateParameter(unsigned Depth,
unsigned Position) {
EnterExpressionEvaluationContext ConstantEvaluated(
Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
DefaultArg = Actions.CorrectDelayedTyposInExpr(ParseInitializer());
+ if (DefaultArg.isUsable())
+ DefaultArg = Actions.ActOnConstantExpression(DefaultArg);
if (DefaultArg.isInvalid())
SkipUntil(tok::comma, tok::greater, StopAtSemi | StopBeforeMatch);
}
diff --git a/clang/test/SemaCXX/cxx2a-template-lambdas.cpp
b/clang/test/SemaCXX/cxx2a-template-lambdas.cpp
index fff524e77d3bf4..ec373f30876295 100644
--- a/clang/test/SemaCXX/cxx2a-template-lambdas.cpp
+++ b/clang/test/SemaCXX/cxx2a-template-lambdas.cpp
@@ -97,3 +97,22 @@ void foo() {
}
#endif
+
+#if __cplusplus >= 202002L
+void GH107048() {
+ constexpr int x{};
+ const int y{};
+ auto b = []<int=x, int=y>{};
+ using A = decltype([]<int=x>{});
+
+ int z; // expected-note {{'z' declared here}}
+ auto c = []<int t=z>{
+ // expected-error@-1 {{no matching function for call to object of type}} \
+ // expected-error@-1 {{variable 'z' cannot be implicitly captured in a
lambda with no capture-default specified}} \
+ // expected-note@-1 {{lambda expression begins here}} \
+ // expected-note@-1 4{{capture}} \
+ // expected-note@-1 {{candidate template ignored: substitution failure:
reference to local variable 'z' declared in enclosing function}}
+ return t;
+ }();
+}
+#endif
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