[PATCH] D140554: [C++20] Determine the dependency of unevaluated lambdas more accurately

[Liming Liu via Phabricator via cfe-commits]

lime updated this revision to Diff 486764.
lime added a comment.

Just rebased, and the `check-profile` target passed on my local machine.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D140554/new/

https://reviews.llvm.org/D140554

Files:
  clang/docs/ReleaseNotes.rst
  clang/include/clang/Sema/Sema.h
  clang/lib/Sema/TreeTransform.h
  clang/test/CodeGenCXX/cxx20-unevaluated-lambda-crash.cpp
  clang/test/SemaCXX/lambda-unevaluated.cpp


Index: clang/test/SemaCXX/lambda-unevaluated.cpp
===================================================================
--- clang/test/SemaCXX/lambda-unevaluated.cpp
+++ clang/test/SemaCXX/lambda-unevaluated.cpp
@@ -61,9 +61,7 @@
 // Same.
 template<int N> void g(const char (*)[([]{ return N; })()]) {} // expected-note {{candidate}}
 template<int N> void g(const char (*)[([]{ return N; })()]) {} // expected-note {{candidate}}
-// FIXME: We instantiate the lambdas into the context of the function template,
-//  so we think they're dependent and can't evaluate a call to them.
-void use_g() { g<6>(&"hello"); } // expected-error {{no matching function}}
+void use_g() { g<6>(&"hello"); } // expected-error {{ambiguous}}
 }
 
 namespace GH51416 {
Index: clang/test/CodeGenCXX/cxx20-unevaluated-lambda-crash.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/cxx20-unevaluated-lambda-crash.cpp
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++20 %s -emit-llvm -o - | FileCheck %s
+
+// CHECK-LABEL: define linkonce_odr void @"_ZN10Issue579601EIiEENS_1FILNS_3$_0EEEEv"()
+namespace Issue57960 {
+template<auto>
+class F {};
+
+template<typename D>
+F<[]{}> E() {
+    return {};
+}
+
+static auto f = E<int>();
+}
Index: clang/lib/Sema/TreeTransform.h
===================================================================
--- clang/lib/Sema/TreeTransform.h
+++ clang/lib/Sema/TreeTransform.h
@@ -13234,10 +13234,11 @@
   // context that isn't a DeclContext (such as a variable template), or when
   // substituting an unevaluated lambda inside of a function's parameter's type
   // - as parameter types are not instantiated from within a function's DC. We
-  // use isUnevaluatedContext() to distinguish the function parameter case.
+  // use evaluation contexts to distinguish the function parameter case.
   CXXRecordDecl::LambdaDependencyKind DependencyKind =
       CXXRecordDecl::LDK_Unknown;
-  if (getSema().isUnevaluatedContext() &&
+  if ((getSema().isUnevaluatedContext() ||
+       getSema().isConstantEvaluatedContext()) &&
       (getSema().CurContext->isFileContext() ||
        !getSema().CurContext->getParent()->isDependentContext()))
     DependencyKind = CXXRecordDecl::LDK_NeverDependent;
Index: clang/include/clang/Sema/Sema.h
===================================================================
--- clang/include/clang/Sema/Sema.h
+++ clang/include/clang/Sema/Sema.h
@@ -9624,6 +9624,12 @@
     return ExprEvalContexts.back().isUnevaluated();
   }
 
+  bool isConstantEvaluatedContext() const {
+    assert(!ExprEvalContexts.empty() &&
+           "Must be in an expression evaluation context");
+    return ExprEvalContexts.back().isConstantEvaluated();
+  }
+
   bool isImmediateFunctionContext() const {
     assert(!ExprEvalContexts.empty() &&
            "Must be in an expression evaluation context");
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -338,6 +338,8 @@
 - In C mode, when ``e1`` has ``__attribute__((noreturn))`` but ``e2`` doesn't,
   ``(c ? e1 : e2)`` is no longer considered noreturn.
   `Issue 59792 <https://github.com/llvm/llvm-project/issues/59792>`_
+- Fix an issue that makes Clang crash on lambda template parameters. This fixes
+  `Issue 57960 <https://github.com/llvm/llvm-project/issues/57960>`_
 
 Improvements to Clang's diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


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