[Basic] Add const qualifier to SM.isInSystemMacro (NFC)

The member function is a predicate, and doesn't apply any changes on the
object.

Patch by Visoiu Mistrih Francis!

Differential Revision: https://reviews.llvm.org/D23433

llvm-svn: 278444

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/include/clang/Basic/SourceManager.h b/clang/include/clang/Basic/SourceManager.h
index e00c99e4ade..6610c56b15d 100644
--- a/clang/include/clang/Basic/SourceManager.h
+++ b/clang/include/clang/Basic/SourceManager.h
@@ -1357,7 +1357,7 @@ public:
   }
 
   /// \brief Returns whether \p Loc is expanded from a macro in a system header.
-  bool isInSystemMacro(SourceLocation loc) {
+  bool isInSystemMacro(SourceLocation loc) const {
     return loc.isMacroID() && isInSystemHeader(getSpellingLoc(loc));
   }