[verify] Add support for location markers in directives.

A marker (matching /#[A-Za-z0-9_-]/) is specified by attaching a comment
containing the marker to the line at which the diagnostic is expected,
and then can be referenced from an expected-* directive after an @:

  foo // #1
  // expected-error@#1 {{undeclared identifier 'foo'}}

The intent is for markers to be used in situations where relative line
numbers are currently used, to avoid the need to renumber when the test
case is rearranged.

llvm-svn: 358326

Author: zygoloid

clang/include/clang/Basic/DiagnosticFrontendKinds.td

@@ -121,6 +121,12 @@ def err_verify_missing_file : Error<
     "file '%0' could not be located in expected %1">;
 def err_verify_invalid_range : Error<
     "invalid range following '-' in expected %0">;
+def err_verify_ambiguous_marker : Error<
+    "reference to marker '%0' is ambiguous">;
+def note_verify_ambiguous_marker : Note<
+    "ambiguous marker '%0' is defined here">;
+def err_verify_no_such_marker : Error<
+    "use of undefined marker '%0'">;
 def err_verify_missing_start : Error<
     "cannot find start ('{{') of expected %0">;
 def err_verify_missing_end : Error<

clang/include/clang/Frontend/VerifyDiagnosticConsumer.h

@@ -81,6 +81,19 @@ class TextDiagnosticBuffer;
 /// the included file is, for example, a system header where the actual line
 /// number may change and is not critical).
 ///
+/// As an alternative to specifying a fixed line number, the location of a
+/// diagnostic can instead be indicated by a marker of the form "#<marker>".
+/// Markers are specified by including them in a comment, and then referenced
+/// by appending the marker to the diagnostic with "@#<marker>":
+///
+/// \code
+///   #warning some text  // #1
+///   // expected-warning@#1 {{some text}}
+/// \endcode
+///
+/// The name of a marker used in a directive must be unique within the
+/// compilation.
+///
 /// The simple syntax above allows each specification to match exactly one
 /// error.  You can use the extended syntax to customize this. The extended
 /// syntax is "expected-<type> <n> {{diag text}}", where \<type> is one of
@@ -212,11 +225,14 @@ class VerifyDiagnosticConsumer: public DiagnosticConsumer,
     HasOtherExpectedDirectives
   };
 
+  class MarkerTracker;
+
 private:
   DiagnosticsEngine &Diags;
   DiagnosticConsumer *PrimaryClient;
   std::unique_ptr<DiagnosticConsumer> PrimaryClientOwner;
   std::unique_ptr<TextDiagnosticBuffer> Buffer;
+  std::unique_ptr<MarkerTracker> Markers;
   const Preprocessor *CurrentPreprocessor = nullptr;
   const LangOptions *LangOpts = nullptr;
   SourceManager *SrcManager = nullptr;