Correct invalid end location in diagnostics for some identifiers.

[erikjv]

Summary

Declaration names in DeclSpec had only their start set to a valid
location, so when the type specifier was missing, only the carret would
be shown at the first character of the name of a member declaration. Now
the whole identifier is underlined, which is useful for IDEs using
libclang.

Also, when the lookup for an identifier-expression failed, the end
location for that identifier was invalid.

Fixes PR25374.

[erikjv]

Wrong patch

lib/Lex/Lexer.cpp

std::pair<unsigned, bool> Lexer::ComputePreamble(StringRef Buffer,
   TheLexer.SetCommentRetentionState(true);
 
   // StartLoc will differ from FileLoc if there is a BOM that was skipped.
   SourceLocation StartLoc = TheLexer.getSourceLocation();
 
   bool InPreprocessorDirective = false;
   Token TheTok;
   Token IfStartTok;
-  unsigned IfCount = 0;
+  int IfCount = 0;
   SourceLocation ActiveCommentLoc;
 
   unsigned MaxLineOffset = 0;
   if (MaxLines) {
     const char *CurPtr = Buffer.begin();
     unsigned CurLine = 0;
     while (CurPtr != Buffer.end()) {
       char ch = *CurPtr++;
if (TheTok.isAtStartOfLine() && TheTok.getKind() == tok::hash) {
           if (IfCount == 0)
             IfStartTok = HashTok;
             
           ++IfCount;
           continue;
             
         case PDK_EndIf:
           // Mismatched #endif. The preamble ends here.
-          if (IfCount == 0)
+          if (IfCount == 0) {
+            --IfCount;
             break;
+          }
 
           --IfCount;
           continue;
             
         case PDK_Unknown:
           // We don't know what this directive is; stop at the '#'.
           break;
         }
       }
       
       // We only end up here if we didn't recognize the preprocessor
       // directive or it was one that can't occur in the preamble at this
       // point. Roll back the current token to the location of the '#'.
       InPreprocessorDirective = false;
       TheTok = HashTok;
     }
 
     // We hit a token that we don't recognize as being in the
     // "preprocessing only" part of the file, so we're no longer in
     // the preamble.
     break;
   } while (true);
   
   SourceLocation End;
-  if (IfCount)
+  if (IfCount < 0) // This allows for open #ifs, so a header with an include
+                   // guard will have a preamble generated for it.
     End = IfStartTok.getLocation();
   else if (ActiveCommentLoc.isValid())
     End = ActiveCommentLoc; // don't truncate a decl comment.
   else
     End = TheTok.getLocation();
 
   return std::make_pair(End.getRawEncoding() - StartLoc.getRawEncoding(),
                         IfCount? IfStartTok.isAtStartOfLine()

test/Lexer/preamble.c

 // Preamble detection test: see below for comments and test commands.
 //* A BCPL comment that includes '/*'
 #include <blah>
 #ifndef FOO
 #else
 #ifdef BAR
 #elif WIBBLE
 #endif
 #pragma unknown
 #endif
 #ifdef WIBBLE
-#include "honk"
-#else
-int foo();
+#include "foo"
+int bar;
 #endif
 
 // This test checks for detection of the preamble of a file, which
-// includes all of the starting comments and #includes. Note that any
-// changes to the preamble part of this file must be mirrored in
-// Inputs/preamble.txt, since we diff against it.
+// includes all of the starting comments and #includes.
 
 // RUN: %clang_cc1 -print-preamble %s > %t
 // RUN: echo END. >> %t
 // RUN: FileCheck < %t %s
 
 // CHECK: // Preamble detection test: see below for comments and test commands.
 // CHECK-NEXT: //* A BCPL comment that includes '/*'
 // CHECK-NEXT: #include <blah>
 // CHECK-NEXT: #ifndef FOO
 // CHECK-NEXT: #else
 // CHECK-NEXT: #ifdef BAR
 // CHECK-NEXT: #elif WIBBLE
 // CHECK-NEXT: #endif
 // CHECK-NEXT: #pragma unknown
 // CHECK-NEXT: #endif
+// CHECK-NEXT: #ifdef WIBBLE
+// CHECK-NEXT: #include "foo"
 // CHECK-NEXT: END.

test/Lexer/preamble2.c

+// Preamble detection test: header with an include guard.
+#ifndef HEADER_H
+#define HEADER_H
+#include "foo"
+int bar;
+#endif
+
+// This test checks for detection of the preamble of a file, which
+// includes all of the starting comments and #includes.
+
+// RUN: %clang_cc1 -print-preamble %s > %t
+// RUN: echo END. >> %t
+// RUN: FileCheck < %t %s
+
+// CHECK: // Preamble detection test: header with an include guard.
+// CHECK-NEXT: #ifndef HEADER_H
+// CHECK-NEXT: #define HEADER_H
+// CHECK-NEXT: #include "foo"
+// CHECK-NEXT: END.