[clang] [FixIt] Improve Source Ranges and Fix-It Hints for Unused Lambda Captures #106445 (PR #117953)

[Oliver Hunt via cfe-commits]

================
@@ -1207,12 +1222,61 @@ void Sema::ActOnLambdaExpressionAfterIntroducer(LambdaIntroducer &Intro,
       // for e.g., [n{0}] { }; <-- if no <initializer_list> is included.
       // FIXME: we should create the init capture variable and mark it invalid
       // in this case.
-      if (C->InitCaptureType.get().isNull())
-        continue;
+      // Ensure the initialization is valid before proceeding
+
+      if (!C->InitCaptureType || C->InitCaptureType.get().isNull()) {
+        if (!C->Init.isUsable()) {
+          Diag(C->Loc, diag::err_invalid_lambda_capture_initializer_type);
+          continue;
+        }
+
+        if (!C->Init.get()) {
+          continue;
+        }
 
-      if (C->Init.get()->containsUnexpandedParameterPack() &&
-          !C->InitCaptureType.get()->getAs<PackExpansionType>())
-        DiagnoseUnexpandedParameterPack(C->Init.get(), UPPC_Initializer);
+        ASTContext &Ctx = this->Context;
+        QualType DeducedType = C->Init.get()->getType();
+
+        if (DeducedType.isNull()) {
+          continue;
+        }
+
+        if (DeducedType->isVoidType()) {
+          if (!DeducedType->isDependentType()) {
+            C->InitCaptureType = ParsedType::make(Ctx.DependentTy);
+          } else {
+            Diag(C->Loc, diag::err_invalid_lambda_capture_initializer_type);
+          }
+          continue;
+        }
+
+        if (isa<InitListExpr>(C->Init.get())) {
+          IdentifierInfo *DummyID = &Ctx.Idents.get("lambda_tmp_var");
+          QualType DummyType = Ctx.UnknownAnyTy;
+
+          auto *TempVarDecl =
+              VarDecl::Create(Ctx, nullptr, C->Loc, C->Loc, DummyID, DummyType,
+                              nullptr, SC_None);
+
+          if (!TempVarDecl) {
+            continue;
+          }
+
+          DeducedType = deduceVarTypeFromInitializer(
+              TempVarDecl, TempVarDecl->getDeclName(), TempVarDecl->getType(),
+              nullptr, TempVarDecl->getSourceRange(), false, C->Init.get());
+
+          if (DeducedType.isNull()) {
+            Diag(C->Loc, diag::err_invalid_lambda_capture_initializer_type);
+            C->InitCaptureType = ParsedType::make(Ctx.DependentTy);
+            continue;
+          }
+        }
+
+        if (!DeducedType.isNull()) {
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ojhunt wrote:

excess braces

https://github.com/llvm/llvm-project/pull/117953