[clang][AST] Invalidate DecompositionDecl if it has invalid initializer.

Fix #67495, #72198

Author: hokein

clang/lib/Sema/SemaDecl.cpp

@@ -13602,6 +13602,15 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init, bool DirectInit) {
           CreateRecoveryExpr(Init->getBeginLoc(), Init->getEndLoc(), Args);
       if (RecoveryExpr.get())
         VDecl->setInit(RecoveryExpr.get());
+      // In general, for error recovery purposes, the initalizer doesn't play
+      // part in the valid bit of the declaration. There are a few exceptions:
+      //  1) if the var decl has a deduced auto type, and the type cannot be
+      //     deduced by an invalid initializer;
+      //  2) if the var decl is decompsition decl with a concrete type (e.g.
+      //    `int [a, b] = 1;`), and the initializer is invalid;
+      // Case 1) is already handled earlier in this function.
+      if (llvm::isa<DecompositionDecl>(VDecl)) // Case 2)
+        VDecl->setInvalidDecl();
       return;
     }
 

clang/test/AST/ast-dump-invalid-initialized.cpp

@@ -24,4 +24,17 @@ void test() {
   auto b4 = A(1);
   // CHECK: `-VarDecl {{.*}} invalid b5 'auto'
   auto b5 = A{1};
-}
+}
+
+void pr72198() {
+  // CHECK: DecompositionDecl {{.*}} invalid 'int'
+  int [_, b] = {0, 0};
+  [b]{};
+}
+
+int get_point();
+void pr67495() {
+  // CHECK: DecompositionDecl {{.*}} invalid 'int &'
+  auto& [x, y] = get_point();
+  [x, y] {};
+}