[Sema] Fix fixit cast printing inside macros (#66853)

`Lexer::getLocForEndOfToken` is documented as returning an invalid
source location when the end of the token is inside a macro expansion.
We don't want that for this particular application, so just calculate
the end location directly instead.

Before this, format fix-its would omit the closing parenthesis (thus
producing invalid code) for macros, e.g.:

```
$ cat format.cpp
extern "C" int printf(const char *, ...);
enum class Foo { Bar };
#define LOG(...) printf(__VA_ARGS__)
void f(Foo foo) { LOG("%d\n", foo); }

$ clang -fsyntax-only format.cpp
format.cpp:4:29: warning: format specifies type 'int' but the argument has type 'Foo' [-Wformat]
    4 | void f(Foo f) { LOG("%d\n", f); }
      |                      ~~     ^
      |                             static_cast<int>(
format.cpp:3:25: note: expanded from macro 'LOG'
    3 | #define LOG(...) printf(__VA_ARGS__)
      |                         ^~~~~~~~~~~
1 warning generated.
```

We now emit a valid fix-it:

```
$ clang -fsyntax-only format.cpp
format.cpp:4:31: warning: format specifies type 'int' but the argument has type 'Foo' [-Wformat]
    4 | void f(Foo foo) { LOG("%d\n", foo); }
      |                        ~~     ^~~
      |                               static_cast<int>( )
format.cpp:3:25: note: expanded from macro 'LOG'
    3 | #define LOG(...) printf(__VA_ARGS__)
      |                         ^~~~~~~~~~~
1 warning generated.
```

Fixes https://github.com/llvm/llvm-project/issues/63462

1 files changed, 5 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index fad7022..b867d55 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -11470,7 +11470,11 @@ CheckPrintfHandler::checkFormatExpr(const analyze_printf::PrintfSpecifier &FS,
         Hints.push_back(
             FixItHint::CreateInsertion(E->getBeginLoc(), CastFix.str()));
 
-        SourceLocation After = S.getLocForEndOfToken(E->getEndLoc());
+        // We don't use getLocForEndOfToken because it returns invalid source
+        // locations for macro expansions (by design).
+        SourceLocation EndLoc = S.SourceMgr.getSpellingLoc(E->getEndLoc());
+        SourceLocation After = EndLoc.getLocWithOffset(
+            Lexer::MeasureTokenLength(EndLoc, S.SourceMgr, S.LangOpts));
         Hints.push_back(FixItHint::CreateInsertion(After, ")"));
       }