[clang] Fix CTAD not work for C++ explicit type conversion (functional annotation). (#75779)

This fixes https://github.com/llvm/llvm-project/issues/64347.

The CTAD for an aggregate class is missing to handle the explicit type
conversion case, e.g. `TemplateFooClass(1, 2);`. Per C++ expr.type.conv
p1, the deduced type is the return type of the deduction guide selected
by the CTAD for the reminder.

In the deduction implementation
`DeduceTemplateSpecializationFromInitializer`, the parenthesized
express-list case relies on the `ParenListExpr` parameter (default is
nullptr), the AST `ParenListExpr` node is not built for all variant
initializer cases (`BuildCXXTypeConstructorExpr`, `BuildCXXNew` etc),
thus the deduction doesn't perform for these cases. This patch fixes it
by removing the `ParenListExpr` and using the `Inits` instead (which
also simplifies the interface and implementation).

1 files changed, 7 insertions, 4 deletions

diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index d6459fd..0fbd87c 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -10561,7 +10561,7 @@ static bool isOrIsDerivedFromSpecializationOf(CXXRecordDecl *RD,
 
 QualType Sema::DeduceTemplateSpecializationFromInitializer(
     TypeSourceInfo *TSInfo, const InitializedEntity &Entity,
-    const InitializationKind &Kind, MultiExprArg Inits, ParenListExpr *PL) {
+    const InitializationKind &Kind, MultiExprArg Inits) {
   auto *DeducedTST = dyn_cast<DeducedTemplateSpecializationType>(
       TSInfo->getType()->getContainedDeducedType());
   assert(DeducedTST && "not a deduced template specialization type");
@@ -10792,9 +10792,12 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
     if (getLangOpts().CPlusPlus20 && !HasAnyDeductionGuide) {
       if (ListInit && ListInit->getNumInits()) {
         SynthesizeAggrGuide(ListInit);
-      } else if (PL && PL->getNumExprs()) {
-        InitListExpr TempListInit(getASTContext(), PL->getLParenLoc(),
-                                  PL->exprs(), PL->getRParenLoc());
+      } else if (Inits.size()) { // parenthesized expression-list
+        // Inits are expressions inside the parentheses. We don't have
+        // the parentheses source locations, use the begin/end of Inits as the
+        // best heuristic.
+        InitListExpr TempListInit(getASTContext(), Inits.front()->getBeginLoc(),
+                                  Inits, Inits.back()->getEndLoc());
         SynthesizeAggrGuide(&TempListInit);
       }
     }