[clang] [clang-format] Fix a crash in `QualifierAlignment: Right` (PR #120821)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-format

Author: Owen Pan (owenca)

<details>
<summary>Changes</summary>

Fixes #<!-- -->120793.

---
Full diff: https://github.com/llvm/llvm-project/pull/120821.diff


2 Files Affected:

- (modified) clang/lib/Format/QualifierAlignmentFixer.cpp (+1-1) 
- (modified) clang/unittests/Format/QualifierFixerTest.cpp (+5) 


``````````diff
diff --git a/clang/lib/Format/QualifierAlignmentFixer.cpp b/clang/lib/Format/QualifierAlignmentFixer.cpp
index 593f8efff25aa9..530b2dd538cee0 100644
--- a/clang/lib/Format/QualifierAlignmentFixer.cpp
+++ b/clang/lib/Format/QualifierAlignmentFixer.cpp
@@ -348,7 +348,7 @@ const FormatToken *LeftRightQualifierAlignmentFixer::analyzeRight(
       }
     }
 
-    if (Next->is(tok::kw_auto))
+    if (Next && Next->is(tok::kw_auto))
       TypeToken = Next;
 
     // Place the Qualifier at the end of the list of qualifiers.
diff --git a/clang/unittests/Format/QualifierFixerTest.cpp b/clang/unittests/Format/QualifierFixerTest.cpp
index f9255c6e4c7088..9ed567445eb07e 100644
--- a/clang/unittests/Format/QualifierFixerTest.cpp
+++ b/clang/unittests/Format/QualifierFixerTest.cpp
@@ -531,6 +531,11 @@ TEST_F(QualifierFixerTest, RightQualifier) {
   verifyFormat("float (C::*const p)(int);", Style);
   verifyFormat("float (C::*p)(int) const;", Style);
   verifyFormat("float const (C::*p)(int);", "const float (C::*p)(int);", Style);
+
+  Style.BreakBeforeBraces = FormatStyle::BS_Custom;
+  Style.BraceWrapping.AfterFunction = true;
+  verifyFormat("auto foo() -> T const { return bar; }",
+               "auto foo() -> const T { return bar; }", Style);
 }
 
 TEST_F(QualifierFixerTest, LeftQualifier) {

``````````

</details>


https://github.com/llvm/llvm-project/pull/120821