[clang] [Clang] Handle sema of noexcept condition in their evaluation context. (PR #67538)

[via cfe-commits]

https://github.com/cor3ntin created https://github.com/llvm/llvm-project/pull/67538

The conditions of a noexcept and explicit specifier are full expressions. Before this patch, we would call ActOnFinishFullExpr on these in the context of the enclosing expression, which would cause the collect of odr-used variables (and subsequently capture attempts) in the wrong (enclosing) context.

This was observable when parsing the noexcept specifier condition of a lambda appearing in a wider full expression odr-using variables.

Fixes #67492

>From 812579329cee47f8d6ddb04f3ddd5af2f56f79a3 Mon Sep 17 00:00:00 2001
From: Corentin Jabot <corentinjabot at gmail.com>
Date: Wed, 27 Sep 2023 12:29:33 +0200
Subject: [PATCH] [Clang] Handle sema of noexcept condition in their evaluation
 context.

The conditions of a noexcept and explicit specifier are full expressions.
Before this patch, we would call ActOnFinishFullExpr on these in the context
of the enclosing expression, which would cause the collect of odr-used variables
(and subsequently capture attempts) in the wrong (enclosing) context.

This was observable when parsing the noexcept specifier condition of a
lambda appearing in a wider full expression odr-using variables.

Fixes #67492
---
 clang/docs/ReleaseNotes.rst               | 4 ++++
 clang/lib/Parse/ParseDecl.cpp             | 6 +++++-
 clang/lib/Parse/ParseDeclCXX.cpp          | 6 +++++-
 clang/test/SemaCXX/lambda-expressions.cpp | 5 +++++
 4 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index a17efab57bcdfa3..d74cd46c3bfccc6 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -363,6 +363,10 @@ Bug Fixes to C++ Support
   reference. Fixes:
   (`#64162 <https://github.com/llvm/llvm-project/issues/64162>`_)
 
+- Clang no longer tries to capture non-odr-used variables that appear
+  in the enclosing expression of a lambda expression with a noexcept specifier.
+  (`#67492 <https://github.com/llvm/llvm-project/issues/67492>`_)
+
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 - Fixed an import failure of recursive friend class template.
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index f5b4107cc32c1f0..735d7a861c7bead 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -4162,7 +4162,11 @@ void Parser::ParseDeclarationSpecifiers(
           ExprResult ExplicitExpr(static_cast<Expr *>(nullptr));
           BalancedDelimiterTracker Tracker(*this, tok::l_paren);
           Tracker.consumeOpen();
-          ExplicitExpr = ParseConstantExpression();
+
+          EnterExpressionEvaluationContext ConstantEvaluated(
+              Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
+
+          ExplicitExpr = ParseConstantExpressionInExprEvalContext();
           ConsumedEnd = Tok.getLocation();
           if (ExplicitExpr.isUsable()) {
             CloseParenLoc = Tok.getLocation();
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index e5a278c598cfb63..6cae537ed21e215 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -3988,7 +3988,11 @@ ExceptionSpecificationType Parser::tryParseExceptionSpecification(
     // There is an argument.
     BalancedDelimiterTracker T(*this, tok::l_paren);
     T.consumeOpen();
-    NoexceptExpr = ParseConstantExpression();
+
+    EnterExpressionEvaluationContext ConstantEvaluated(
+        Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
+    NoexceptExpr = ParseConstantExpressionInExprEvalContext();
+
     T.consumeClose();
     if (!NoexceptExpr.isInvalid()) {
       NoexceptExpr =
diff --git a/clang/test/SemaCXX/lambda-expressions.cpp b/clang/test/SemaCXX/lambda-expressions.cpp
index 0c9e8584e653473..9cf81a0a195a573 100644
--- a/clang/test/SemaCXX/lambda-expressions.cpp
+++ b/clang/test/SemaCXX/lambda-expressions.cpp
@@ -718,3 +718,8 @@ void foo() {
 void GH48527() {
   auto a = []()__attribute__((b(({ return 0; })))){}; // expected-warning {{unknown attribute 'b' ignored}}
 }
+
+void GH67492() {
+  constexpr auto test = 42;
+  auto lambda = (test, []() noexcept(true) {});
+}