[clang] [clang] ast-text-dump: fix printing of declref to decomposition with no bindings. (PR #199215)

[Matheus Izvekov via cfe-commits]

https://github.com/mizvekov created https://github.com/llvm/llvm-project/pull/199215

Clang supports empty structured binding groups as an extension, and the text node dumper has some special handling for giving a name to anonymous declarations, which assumed a decomposition would have at least one binding.

Fixes #198842

>From 7aa3039afe3d89d8610937a1795aef185d28abef Mon Sep 17 00:00:00 2001
From: Matheus Izvekov <mizvekov at gmail.com>
Date: Fri, 22 May 2026 10:20:12 -0300
Subject: [PATCH] [clang] ast-text-dump: fix printing of declref to
 decomposition with no bindings.

Clang supports empty structured binding groups as an extension,
and the text node dumper has some special handling for giving a name
to anonymous declarations, which assumed a decomposition would have at
least one binding.

Fixes #198842
---
 clang/docs/ReleaseNotes.rst      |  2 ++
 clang/lib/AST/TextNodeDumper.cpp | 10 ++++++----
 clang/test/AST/ast-dump-decl.cpp |  8 ++++++++
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index a9017f44058be..fa3777f1c24b3 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -676,6 +676,8 @@ Bug Fixes to AST Handling
 
 Miscellaneous Bug Fixes
 ^^^^^^^^^^^^^^^^^^^^^^^
+- Fixed a crash whith the AST text dumper, when dumping a reference to a
+  decomposition with no bindinds. (#GH198842)
 - Fixed the arguments of the format attribute on ``__builtin_os_log_format``.  Previously, they were off by 1.
 
 Miscellaneous Clang Crashes Fixed
diff --git a/clang/lib/AST/TextNodeDumper.cpp b/clang/lib/AST/TextNodeDumper.cpp
index e474517f56e6d..2b1c0cac25b6d 100644
--- a/clang/lib/AST/TextNodeDumper.cpp
+++ b/clang/lib/AST/TextNodeDumper.cpp
@@ -966,11 +966,13 @@ void TextNodeDumper::dumpBareDeclRef(const Decl *D) {
       OS << " '" << Name << '\'';
     else
       switch (ND->getKind()) {
-      case Decl::Decomposition: {
-        auto *DD = cast<DecompositionDecl>(ND);
-        OS << " first_binding '" << DD->bindings()[0]->getDeclName() << '\'';
+      case Decl::Decomposition:
+        if (auto Bindings = cast<DecompositionDecl>(ND)->bindings();
+            !Bindings.empty())
+          OS << " first_binding '" << Bindings[0]->getDeclName() << '\'';
+        else
+          OS << " no_bindings";
         break;
-      }
       case Decl::Field: {
         auto *FD = cast<FieldDecl>(ND);
         OS << " field_index " << FD->getFieldIndex();
diff --git a/clang/test/AST/ast-dump-decl.cpp b/clang/test/AST/ast-dump-decl.cpp
index a750375f5e62b..9b745642aedd0 100644
--- a/clang/test/AST/ast-dump-decl.cpp
+++ b/clang/test/AST/ast-dump-decl.cpp
@@ -1005,3 +1005,11 @@ namespace TestGH155936 {
   // CHECK: CXXRecordDecl 0x{{.+}} <line:[[@LINE-8]]:7, col:19> col:14 struct Foo definition
   // CHECH: CXXRecordDecl 0x{{.+}} <col:9, col:16> col:16 implicit struct Foo
 } // namspace GH155936
+
+namespace TestGH198842 {
+  struct X {};
+  auto && [] = X{};
+  // CHECK-LABEL: Dumping TestGH198842:
+  // CHECK: DecompositionDecl 0x{{.+}} <line:{{.+}}:3, col:18> col:11 'X &&' cinit external-linkage
+  // CHECK: MaterializeTemporaryExpr 0x{{.+}} <col:16, col:18> 'X' xvalue extended by Decomposition 0x{{.+}} no_bindings 'X &&'
+} // namespace TestGH198842