[Clang] SemaFunctionEffects: Fix bug where lambdas produced by template expansion weren't verified. (#116505)

---------

Co-authored-by: Doug Wyatt <dwyatt@apple.com>

clang/lib/Sema/SemaFunctionEffects.cpp

@@ -807,7 +807,8 @@ private:
 
     auto MaybeAddTemplateNote = [&](const Decl *D) {
       if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
-        while (FD != nullptr && FD->isTemplateInstantiation()) {
+        while (FD != nullptr && FD->isTemplateInstantiation() &&
+               FD->getPointOfInstantiation().isValid()) {
           S.Diag(FD->getPointOfInstantiation(),
                  diag::note_func_effect_from_template);
           FD = FD->getTemplateInstantiationPattern();

clang/lib/Sema/SemaLambda.cpp

@@ -1950,8 +1950,6 @@ ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body) {
   LambdaScopeInfo LSI = *cast<LambdaScopeInfo>(FunctionScopes.back());
   ActOnFinishFunctionBody(LSI.CallOperator, Body);
 
-  maybeAddDeclWithEffects(LSI.CallOperator);
-
   return BuildLambdaExpr(StartLoc, Body->getEndLoc(), &LSI);
 }
 
@@ -2284,6 +2282,7 @@ ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
     case ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed:
       break;
     }
+    maybeAddDeclWithEffects(LSI->CallOperator);
   }
 
   return MaybeBindToTemporary(Lambda);

clang/test/Sema/attr-nonblocking-constraints.cpp

@@ -144,6 +144,41 @@ void nb9() [[clang::nonblocking]]
 		expected-note {{in template expansion here}}
 }
 
+// Make sure we verify lambdas produced from template expansions.
+struct HasTemplatedLambda {
+	void (*fptr)() [[clang::nonblocking]];
+
+	template <typename C>
+	HasTemplatedLambda(const C&)
+		: fptr{ []() [[clang::nonblocking]] {
+			auto* y = new int; // expected-warning {{lambda with 'nonblocking' attribute must not allocate or deallocate memory}}
+		} }
+	{}
+};
+
+void nb9a()
+{
+	HasTemplatedLambda bad(42);
+}
+
+// Templated function and lambda.
+template <typename T>
+void TemplatedFunc(T x) [[clang::nonblocking]] {
+	auto* ptr = new T; // expected-warning {{function with 'nonblocking' attribute must not allocate or deallocate memory}}
+}
+
+void nb9b() [[clang::nonblocking]] {
+	TemplatedFunc(42); // expected-note {{in template expansion here}}
+
+	auto foo = [](auto x) [[clang::nonblocking]] {
+		auto* ptr = new int; // expected-warning {{lambda with 'nonblocking' attribute must not allocate or deallocate memory}}
+		return x;
+	};
+
+	// Note that foo() won't be validated unless instantiated.
+	foo(42);
+}
+
 void nb10(
 	void (*fp1)(), // expected-note {{function pointer cannot be inferred 'nonblocking'}}
 	void (*fp2)() [[clang::nonblocking]]