Fix a crash when diagnostic points to a macro definition on command line.

[klimek]

LG

clang-tidy/ClangTidyDiagnosticConsumer.cpp

bool ClangTidyDiagnosticConsumer::relatesToUserCode(SourceLocation Location) {
 
   // FIXME: We start with a conservative approach here, but the actual type of
   // location needed depends on the check (in particular, where this check wants
   // to apply fixes).
   FileID FID = Sources.getDecomposedExpansionLoc(Location).first;
   if (FID == Sources.getMainFileID())
     return true;
 
-  return HeaderFilter.match(Sources.getFileEntryForID(FID)->getName());
+  const FileEntry *File = Sources.getFileEntryForID(FID);
+  // -DMACRO definitions on the command line have locations in a virtual buffer
+  // that doesn't have a FileEntry. Don't skip these as well.
+  return !File || HeaderFilter.match(File->getName());
 }
 
 struct LessClangTidyError {
   bool operator()(const ClangTidyError *LHS, const ClangTidyError *RHS) const {
     const ClangTidyMessage &M1 = LHS->Message;
     const ClangTidyMessage &M2 = RHS->Message;
 
     return std::tie(M1.FilePath, M1.FileOffset, M1.Message) <

test/clang-tidy/diagnostic.cpp

 // RUN: clang-tidy -disable-checks='' %s.nonexistent.cpp -- | FileCheck -check-prefix=CHECK1 %s
 // RUN: clang-tidy -disable-checks='' %s -- -fan-unknown-option | FileCheck -check-prefix=CHECK2 %s
 // RUN: clang-tidy -checks='(google-explicit-constructor|clang-diagnostic-literal-conversion)' -disable-checks='' %s -- -fan-unknown-option | FileCheck -check-prefix=CHECK3 %s
+// RUN: clang-tidy -checks='clang-diagnostic-macro-redefined' -disable-checks='' %s -- -DMACRO_FROM_COMMAND_LINE | FileCheck -check-prefix=CHECK4 %s
 
 // CHECK1-NOT: warning
 // CHECK2-NOT: warning
 // CHECK3-NOT: warning
 
 // CHECK1: warning: error reading '{{.*}}.nonexistent.cpp'
 // CHECK2: warning: unknown argument: '-fan-unknown-option'
 
 // CHECK2: :[[@LINE+2]]:9: warning: implicit conversion from 'double' to 'int' changes value
 // CHECK3: :[[@LINE+1]]:9: warning: implicit conversion from 'double' to 'int' changes value
 int a = 1.5;
 
 // CHECK2: :[[@LINE+2]]:11: warning: Single-argument constructors must be explicit [google-explicit-constructor]
 // CHECK3: :[[@LINE+1]]:11: warning: Single-argument constructors must be explicit [google-explicit-constructor]
 class A { A(int) {} };
 
 // CHECK2-NOT: warning:
 // CHECK3-NOT: warning:
+
+#define MACRO_FROM_COMMAND_LINE
+// CHECK4: :[[@LINE-1]]:9: warning: 'MACRO_FROM_COMMAND_LINE' macro redefined