[clang] [analyzer] Fix crash in PaddingChecker on dependent field types (PR #232986)

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<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Manuel Sainz de Baranda y Goñi (redcode)

<details>
<summary>Changes</summary>

Fixes #<!-- -->232874

`PaddingChecker` also visits the implicit closure type of lambda expressions. A lambda with a dependent init-capture inside a `noexcept` specifier of an abbreviated function template is not marked as dependent, so the checker attempted to compute its record layout and crashed in `ASTContext::getTypeInfoImpl` on the dependent field type.

The fix skips records whose fields have dependent types, since their layout cannot be computed.


---
Full diff: https://github.com/llvm/llvm-project/pull/232986.diff


2 Files Affected:

- (modified) clang/lib/StaticAnalyzer/Checkers/PaddingChecker.cpp (+6) 
- (added) clang/test/Analysis/padding_dependent.cpp (+7) 


``````````diff
diff --git a/clang/lib/StaticAnalyzer/Checkers/PaddingChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/PaddingChecker.cpp
index c8d7b6555f3f4..8fbd1831f9175 100644
--- a/clang/lib/StaticAnalyzer/Checkers/PaddingChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/PaddingChecker.cpp
@@ -178,6 +178,12 @@ class PaddingChecker : public Checker<check::ASTDecl<TranslationUnitDecl>> {
       QualType Ty = FD->getType();
       if (Ty->isIncompleteArrayType())
         return true;
+      // Dependent field types have no known layout, so we can't compute the
+      // padding of the enclosing record. This can happen for lambda captures
+      // in a dependent context, e.g. an init-capture of a forwarding reference
+      // inside a noexcept specifier.
+      if (Ty->isDependentType())
+        return true;
       return false;
     };
 
diff --git a/clang/test/Analysis/padding_dependent.cpp b/clang/test/Analysis/padding_dependent.cpp
new file mode 100644
index 0000000000000..ea337d1337950
--- /dev/null
+++ b/clang/test/Analysis/padding_dependent.cpp
@@ -0,0 +1,7 @@
+// RUN: %clang_analyze_cc1 -std=c++20 -analyzer-checker=optin.performance -verify %s
+
+// The static analyzer must not crash when computing the layout of a lambda
+// closure type with a dependent init-capture inside a noexcept specifier.
+// https://github.com/llvm/llvm-project/issues/232874
+// expected-no-diagnostics
+void crasher(auto&& fn) noexcept(noexcept([_ = fn] {})) {}

``````````

</details>


https://github.com/llvm/llvm-project/pull/232986