[llvm-branch-commits] [clang] release/20.x: [Clang] Fix a lambda pattern comparison mismatch after ecc7e6ce4 (#133863) (PR #134194)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (llvmbot)

<details>
<summary>Changes</summary>

Backport dcc2182bc

Requested by: @<!-- -->zyn0217

---
Full diff: https://github.com/llvm/llvm-project/pull/134194.diff


3 Files Affected:

- (modified) clang/lib/Sema/SemaConcept.cpp (-69) 
- (modified) clang/lib/Sema/SemaLambda.cpp (+68) 
- (modified) clang/test/SemaTemplate/concepts-lambda.cpp (+15) 


``````````diff
diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index a7b609f7f3ce4..8adebccde042c 100644
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -702,75 +702,6 @@ bool Sema::CheckConstraintSatisfaction(const Expr *ConstraintExpr,
       .isInvalid();
 }
 
-bool Sema::addInstantiatedCapturesToScope(
-    FunctionDecl *Function, const FunctionDecl *PatternDecl,
-    LocalInstantiationScope &Scope,
-    const MultiLevelTemplateArgumentList &TemplateArgs) {
-  const auto *LambdaClass = cast<CXXMethodDecl>(Function)->getParent();
-  const auto *LambdaPattern = cast<CXXMethodDecl>(PatternDecl)->getParent();
-
-  unsigned Instantiated = 0;
-
-  // FIXME: This is a workaround for not having deferred lambda body
-  // instantiation.
-  // When transforming a lambda's body, if we encounter another call to a
-  // nested lambda that contains a constraint expression, we add all of the
-  // outer lambda's instantiated captures to the current instantiation scope to
-  // facilitate constraint evaluation. However, these captures don't appear in
-  // the CXXRecordDecl until after the lambda expression is rebuilt, so we
-  // pull them out from the corresponding LSI.
-  LambdaScopeInfo *InstantiatingScope = nullptr;
-  if (LambdaPattern->capture_size() && !LambdaClass->capture_size()) {
-    for (FunctionScopeInfo *Scope : llvm::reverse(FunctionScopes)) {
-      auto *LSI = dyn_cast<LambdaScopeInfo>(Scope);
-      if (!LSI ||
-          LSI->CallOperator->getTemplateInstantiationPattern() != PatternDecl)
-        continue;
-      InstantiatingScope = LSI;
-      break;
-    }
-    assert(InstantiatingScope);
-  }
-
-  auto AddSingleCapture = [&](const ValueDecl *CapturedPattern,
-                              unsigned Index) {
-    ValueDecl *CapturedVar =
-        InstantiatingScope ? InstantiatingScope->Captures[Index].getVariable()
-                           : LambdaClass->getCapture(Index)->getCapturedVar();
-    assert(CapturedVar->isInitCapture());
-    Scope.InstantiatedLocal(CapturedPattern, CapturedVar);
-  };
-
-  for (const LambdaCapture &CapturePattern : LambdaPattern->captures()) {
-    if (!CapturePattern.capturesVariable()) {
-      Instantiated++;
-      continue;
-    }
-    ValueDecl *CapturedPattern = CapturePattern.getCapturedVar();
-
-    if (!CapturedPattern->isInitCapture()) {
-      Instantiated++;
-      continue;
-    }
-
-    if (!CapturedPattern->isParameterPack()) {
-      AddSingleCapture(CapturedPattern, Instantiated++);
-    } else {
-      Scope.MakeInstantiatedLocalArgPack(CapturedPattern);
-      SmallVector<UnexpandedParameterPack, 2> Unexpanded;
-      SemaRef.collectUnexpandedParameterPacks(
-          dyn_cast<VarDecl>(CapturedPattern)->getInit(), Unexpanded);
-      auto NumArgumentsInExpansion =
-          getNumArgumentsInExpansionFromUnexpanded(Unexpanded, TemplateArgs);
-      if (!NumArgumentsInExpansion)
-        continue;
-      for (unsigned Arg = 0; Arg < *NumArgumentsInExpansion; ++Arg)
-        AddSingleCapture(CapturedPattern, Instantiated++);
-    }
-  }
-  return false;
-}
-
 bool Sema::SetupConstraintScope(
     FunctionDecl *FD, std::optional<ArrayRef<TemplateArgument>> TemplateArgs,
     const MultiLevelTemplateArgumentList &MLTAL,
diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index ceb32ee15dfa3..981856fbf25a7 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -2389,6 +2389,74 @@ static FunctionDecl *getPatternFunctionDecl(FunctionDecl *FD) {
   return FTD->getTemplatedDecl();
 }
 
+bool Sema::addInstantiatedCapturesToScope(
+    FunctionDecl *Function, const FunctionDecl *PatternDecl,
+    LocalInstantiationScope &Scope,
+    const MultiLevelTemplateArgumentList &TemplateArgs) {
+  const auto *LambdaClass = cast<CXXMethodDecl>(Function)->getParent();
+  const auto *LambdaPattern = cast<CXXMethodDecl>(PatternDecl)->getParent();
+
+  unsigned Instantiated = 0;
+
+  // FIXME: This is a workaround for not having deferred lambda body
+  // instantiation.
+  // When transforming a lambda's body, if we encounter another call to a
+  // nested lambda that contains a constraint expression, we add all of the
+  // outer lambda's instantiated captures to the current instantiation scope to
+  // facilitate constraint evaluation. However, these captures don't appear in
+  // the CXXRecordDecl until after the lambda expression is rebuilt, so we
+  // pull them out from the corresponding LSI.
+  LambdaScopeInfo *InstantiatingScope = nullptr;
+  if (LambdaPattern->capture_size() && !LambdaClass->capture_size()) {
+    for (FunctionScopeInfo *Scope : llvm::reverse(FunctionScopes)) {
+      auto *LSI = dyn_cast<LambdaScopeInfo>(Scope);
+      if (!LSI || getPatternFunctionDecl(LSI->CallOperator) != PatternDecl)
+        continue;
+      InstantiatingScope = LSI;
+      break;
+    }
+    assert(InstantiatingScope);
+  }
+
+  auto AddSingleCapture = [&](const ValueDecl *CapturedPattern,
+                              unsigned Index) {
+    ValueDecl *CapturedVar =
+        InstantiatingScope ? InstantiatingScope->Captures[Index].getVariable()
+                           : LambdaClass->getCapture(Index)->getCapturedVar();
+    assert(CapturedVar->isInitCapture());
+    Scope.InstantiatedLocal(CapturedPattern, CapturedVar);
+  };
+
+  for (const LambdaCapture &CapturePattern : LambdaPattern->captures()) {
+    if (!CapturePattern.capturesVariable()) {
+      Instantiated++;
+      continue;
+    }
+    ValueDecl *CapturedPattern = CapturePattern.getCapturedVar();
+
+    if (!CapturedPattern->isInitCapture()) {
+      Instantiated++;
+      continue;
+    }
+
+    if (!CapturedPattern->isParameterPack()) {
+      AddSingleCapture(CapturedPattern, Instantiated++);
+    } else {
+      Scope.MakeInstantiatedLocalArgPack(CapturedPattern);
+      SmallVector<UnexpandedParameterPack, 2> Unexpanded;
+      SemaRef.collectUnexpandedParameterPacks(
+          dyn_cast<VarDecl>(CapturedPattern)->getInit(), Unexpanded);
+      auto NumArgumentsInExpansion =
+          getNumArgumentsInExpansionFromUnexpanded(Unexpanded, TemplateArgs);
+      if (!NumArgumentsInExpansion)
+        continue;
+      for (unsigned Arg = 0; Arg < *NumArgumentsInExpansion; ++Arg)
+        AddSingleCapture(CapturedPattern, Instantiated++);
+    }
+  }
+  return false;
+}
+
 Sema::LambdaScopeForCallOperatorInstantiationRAII::
     LambdaScopeForCallOperatorInstantiationRAII(
         Sema &SemaRef, FunctionDecl *FD, MultiLevelTemplateArgumentList MLTAL,
diff --git a/clang/test/SemaTemplate/concepts-lambda.cpp b/clang/test/SemaTemplate/concepts-lambda.cpp
index dcb09c76d26b6..1f67c2511e096 100644
--- a/clang/test/SemaTemplate/concepts-lambda.cpp
+++ b/clang/test/SemaTemplate/concepts-lambda.cpp
@@ -325,3 +325,18 @@ template <class> void f() {
 template void f<int>();
 
 }
+
+namespace GH133719 {
+
+template <class T>
+constexpr auto f{[] (auto arg) {
+  return [a{arg}] {
+      [] () requires true {}();
+  };
+}};
+
+void foo() {
+  f<int>(0);
+}
+
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/134194