[clang] Fix default initializers being ignored when initializing templated aggregate types

Previously, when checking whether an in-class initializer exists when
performing parenthesized aggregate initialization, Clang checks that the
output of FieldDecl::getInClassInitializer() is non-null. This is
incorrect; if the field is part of a templated type, then
getInClassInitializer() will return nullptr if we haven't called
Sem::BuildCXXDefaultInitExpr(...) before, even if
FieldDecl::hasInClassInitializer() returns true. The end result is that
Clang incorrectly ignores the in class initializer and
value-initializes the field. The fix therefore is to instead call
FieldDecl::hasInClassInitializer(), which is what we do for braced init
lists [0].

Before this patch, Clang does correctly recognize the in-class field
initializer in certain cases. This is Sema::BuildCXXDefaultInitExpr(...)
populates the in class initializer of the corresponding FieldDecl
object. Therefore, if that method was previously called with the same
FieldDecl object, as can happen with a decltype(...) or a braced list
initialization, FieldDecl::getInClassInitializer() will return a
non-null expression, and the field becomes properly initialized.

Fixes 62266

[0]: https://github.com/llvm/llvm-project/blob/be5f35e24f4c15caf3c4aeccddc54c52560c28a0/clang/lib/Sema/SemaInit.cpp#L685

Reviewed By: shafik

Differential Revision: https://reviews.llvm.org/D149389

1 files changed, 9 insertions, 7 deletions

diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index c218470..55ef72d 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -5377,14 +5377,16 @@ static void TryOrBuildParenListInitialization(
           //   The remaining elements are initialized with their default member
           //   initializers, if any
           auto *FD = cast<FieldDecl>(SubEntity.getDecl());
-          if (Expr *ICE = FD->getInClassInitializer(); ICE && !VerifyOnly) {
-            ExprResult DIE = S.BuildCXXDefaultInitExpr(FD->getLocation(), FD);
-            if (DIE.isInvalid())
-              return false;
-            S.checkInitializerLifetime(SubEntity, DIE.get());
-            InitExprs.push_back(DIE.get());
+          if (FD->hasInClassInitializer()) {
+            if (!VerifyOnly) {
+              ExprResult DIE = S.BuildCXXDefaultInitExpr(FD->getLocation(), FD);
+              if (DIE.isInvalid())
+                return false;
+              S.checkInitializerLifetime(SubEntity, DIE.get());
+              InitExprs.push_back(DIE.get());
+            }
             continue;
-          };
+          }
         }
         // Remaining class elements without default member initializers and
         // array elements are value initialized: