[clang] Fix a crash on CheckArgAlignment.

[hokein]

Summary

We might encounter an undeduced type before calling getTypeAlignInChars.

NOTE: this retrieves the fix from 8f80c66bd2982788a8eede4419684ca72f48b9a2, which was removed in Adam's followup fix fbfcfdbf6828b8d36f4ec0ff5f4eac11fb1411a5. We originally thought the crash was caused by recovery-ast, but it turns out it can occur for other cases, e.g. typo-correction.

[kadircet]

thanks!

clang/lib/Sema/SemaChecking.cpp

void Sema::CheckArgAlignment(SourceLocation Loc, NamedDecl *FDecl,
   if (ParamTy->isPointerType())
     ArgTy = ArgTy->getPointeeType();
 
   // Remove reference or pointer
   ParamTy = ParamTy->getPointeeType();
 
   // Find expected alignment, and the actual alignment of the passed object.
   // getTypeAlignInChars requires complete types
-  if (ParamTy->isIncompleteType() || ArgTy->isIncompleteType())
+  if (ParamTy->isIncompleteType() || ArgTy->isIncompleteType() ||
+      ParamTy->isUndeducedType() || ArgTy->isUndeducedType())
     return;
 
   CharUnits ParamAlign = Context.getTypeAlignInChars(ParamTy);
   CharUnits ArgAlign = Context.getTypeAlignInChars(ArgTy);
 
   // If the argument is less aligned than the parameter, there is a
   // potential alignment issue.
   if (ArgAlign < ParamAlign)

clang/test/SemaCXX/typo-correction-crash.cpp

 namespace NoCrash {
 class S {
   void Function(int a) {
     unknown1(unknown2, Function, unknown3); // expected-error 2{{use of undeclared identifier}} \
                                                expected-error {{reference to non-static member function must be called}}
   }
 };
 }
+
+namespace NoCrashOnCheckArgAlignment {
+template <typename a> void b(a &);
+void test() {
+  for (auto file_data :b(files_db_data)); // expected-error {{use of undeclared identifier 'files_db_data'; did you mean 'file_data'?}} \
+                                          // expected-note {{'file_data' declared here}} \
+                                          // expected-error {{cannot use type 'void' as a range}}
+}
+}