documentation parsing. Patch to do typo correction for

documentation commands. Patch was reviewed, along with
great suggestions for improvement, by Doug. 
// rdar://12381408


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181458 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/AST/CommentCommandTraits.h

@@ -142,6 +142,8 @@ public:
     llvm_unreachable("the command should be known");
   }
 
+  const CommandInfo *getTypoCorrectCommandInfo(StringRef Typo) const;
+  
   const CommandInfo *getCommandInfo(unsigned CommandID) const;
 
   const CommandInfo *registerUnknownCommand(StringRef CommandName);

include/clang/Basic/DiagnosticCommentKinds.td

@@ -159,5 +159,9 @@ def warn_verbatim_block_end_without_start : Warning<
 def warn_unknown_comment_command_name : Warning<
   "unknown command tag name">, InGroup<Documentation>, DefaultIgnore;
 
+def warn_correct_comment_command_name : Warning<
+  "unknown command tag name '%0'; did you mean '%1'?">, 
+  InGroup<Documentation>;
+
 } // end of documentation issue category
 } // end of AST component

lib/AST/CommentCommandTraits.cpp

@@ -43,6 +43,33 @@ const CommandInfo *CommandTraits::getCommandInfo(unsigned CommandID) const {
   return getRegisteredCommandInfo(CommandID);
 }
 
+const CommandInfo *
+CommandTraits::getTypoCorrectCommandInfo(StringRef Typo) const {
+  const unsigned MaxEditDistance = 1;
+  unsigned BestEditDistance = MaxEditDistance + 1;
+  SmallVector<const CommandInfo *, 2> BestCommand;
+  
+  int NumOfCommands = sizeof(Commands) / sizeof(CommandInfo);
+  for (int i = 0; i < NumOfCommands; i++) {
+    StringRef Name = Commands[i].Name;
+    unsigned MinPossibleEditDistance = abs((int)Name.size() - (int)Typo.size());
+    if (MinPossibleEditDistance > 0 &&
+        Typo.size() / MinPossibleEditDistance < 1)
+      continue;
+    unsigned EditDistance = Typo.edit_distance(Name, true, MaxEditDistance);
+    if (EditDistance > MaxEditDistance)
+      continue;
+    if (EditDistance == BestEditDistance)
+      BestCommand.push_back(&Commands[i]);
+    else if (EditDistance < BestEditDistance) {
+      BestCommand.clear();
+      BestCommand.push_back(&Commands[i]);
+      BestEditDistance = EditDistance;
+    }
+  }
+  return (BestCommand.size() != 1) ? NULL : BestCommand[0];
+}
+
 CommandInfo *CommandTraits::createCommandInfoWithName(StringRef CommandName) {
   char *Name = Allocator.Allocate<char>(CommandName.size() + 1);
   memcpy(Name, CommandName.data(), CommandName.size());

lib/AST/CommentLexer.cpp

@@ -265,6 +265,7 @@ const char *findCCommentEnd(const char *BufferPtr, const char *BufferEnd) {
   }
   llvm_unreachable("buffer end hit before '*/' was seen");
 }
+    
 } // unnamed namespace
 
 void Lexer::lexCommentText(Token &T) {
@@ -354,8 +355,17 @@ void Lexer::lexCommentText(Token &T) {
         if (!Info) {
           formTokenWithChars(T, TokenPtr, tok::unknown_command);
           T.setUnknownCommandName(CommandName);
-          Diag(T.getLocation(), diag::warn_unknown_comment_command_name);
-          return;
+          if (Info = Traits.getTypoCorrectCommandInfo(CommandName)) {
+            StringRef CorrectedName = Info->Name;
+            SourceRange CommandRange(T.getLocation().getLocWithOffset(1),
+                                     T.getEndLocation());
+            Diag(T.getLocation(), diag::warn_correct_comment_command_name)
+              << CommandName << CorrectedName
+              << FixItHint::CreateReplacement(CommandRange, CorrectedName);
+          } else {
+            Diag(T.getLocation(), diag::warn_unknown_comment_command_name);
+            return;
+          }
         }
         if (Info->IsVerbatimBlockCommand) {
           setupAndLexVerbatimBlock(T, TokenPtr, *BufferPtr, Info);

test/Sema/warn-documentation-fixits.cpp

@@ -57,6 +57,12 @@ struct test_deprecated_6 {
 /// \deprecated
 void test_deprecated_9(int a);
 
+// rdar://12381408
+// expected-warning@+2  {{unknown command tag name 'retur'; did you mean 'return'?}}
+/// \brief testing fixit
+/// \retur int in FooBar
+int FooBar();
+
 // CHECK: fix-it:"{{.*}}":{5:12-5:22}:"a"
 // CHECK: fix-it:"{{.*}}":{9:12-9:15}:"aaa"
 // CHECK: fix-it:"{{.*}}":{13:13-13:23}:"T"
@@ -68,4 +74,4 @@ void test_deprecated_9(int a);
 // CHECK: fix-it:"{{.*}}":{46:27-46:27}:" __attribute__((deprecated))"
 // CHECK: fix-it:"{{.*}}":{50:27-50:27}:" __attribute__((deprecated))"
 // CHECK: fix-it:"{{.*}}":{58:30-58:30}:" MY_ATTR_DEPRECATED"
-
+// CHECK: fix-it:"{{.*}}":{63:6-63:11}:"return"