[Clang] add typo correction for unknown attribute names (#140629)

This patch enhances Clang's diagnosis for unknown attributes by
providing typo correction suggestions for known attributes.

```cpp
[[gmu::deprected]] // expected-warning {{unknown attribute 'gmu::deprected' ignored; did you mean 'gnu::deprecated'?}}
int f1(void) {
  return 0;
}

[[deprected]] // expected-warning {{unknown attribute 'deprected' ignored; did you mean 'deprecated'?}}
int f2(void) {
  return 0;
}
```

1 files changed, 26 insertions, 71 deletions

diff --git a/clang/lib/AST/CommentSema.cpp b/clang/lib/AST/CommentSema.cpp
index bd2206bb8a3b..fb745fc560d2 100644
--- a/clang/lib/AST/CommentSema.cpp
+++ b/clang/lib/AST/CommentSema.cpp
@@ -13,6 +13,7 @@
 #include "clang/AST/DeclTemplate.h"
 #include "clang/Basic/DiagnosticComment.h"
 #include "clang/Basic/LLVM.h"
+#include "clang/Basic/SimpleTypoCorrection.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Lex/Preprocessor.h"
 #include "llvm/ADT/StringSwitch.h"
@@ -975,69 +976,22 @@ unsigned Sema::resolveParmVarReference(StringRef Name,
   return ParamCommandComment::InvalidParamIndex;
 }
 
-namespace {
-class SimpleTypoCorrector {
-  const NamedDecl *BestDecl;
-
-  StringRef Typo;
-  const unsigned MaxEditDistance;
-
-  unsigned BestEditDistance;
-  unsigned BestIndex;
-  unsigned NextIndex;
-
-public:
-  explicit SimpleTypoCorrector(StringRef Typo)
-      : BestDecl(nullptr), Typo(Typo), MaxEditDistance((Typo.size() + 2) / 3),
-        BestEditDistance(MaxEditDistance + 1), BestIndex(0), NextIndex(0) {}
-
-  void addDecl(const NamedDecl *ND);
-
-  const NamedDecl *getBestDecl() const {
-    if (BestEditDistance > MaxEditDistance)
-      return nullptr;
-
-    return BestDecl;
-  }
+unsigned
+Sema::correctTypoInParmVarReference(StringRef Typo,
+                                    ArrayRef<const ParmVarDecl *> ParamVars) {
+  SimpleTypoCorrection STC(Typo);
+  for (unsigned i = 0, e = ParamVars.size(); i != e; ++i) {
+    const ParmVarDecl *Param = ParamVars[i];
+    if (!Param)
+      continue;
 
-  unsigned getBestDeclIndex() const {
-    assert(getBestDecl());
-    return BestIndex;
+    STC.add(Param->getIdentifier());
   }
-};
-
-void SimpleTypoCorrector::addDecl(const NamedDecl *ND) {
-  unsigned CurrIndex = NextIndex++;
-
-  const IdentifierInfo *II = ND->getIdentifier();
-  if (!II)
-    return;
 
-  StringRef Name = II->getName();
-  unsigned MinPossibleEditDistance = abs((int)Name.size() - (int)Typo.size());
-  if (MinPossibleEditDistance > 0 &&
-      Typo.size() / MinPossibleEditDistance < 3)
-    return;
+  if (STC.hasCorrection())
+    return STC.getCorrectionIndex();
 
-  unsigned EditDistance = Typo.edit_distance(Name, true, MaxEditDistance);
-  if (EditDistance < BestEditDistance) {
-    BestEditDistance = EditDistance;
-    BestDecl = ND;
-    BestIndex = CurrIndex;
-  }
-}
-} // end anonymous namespace
-
-unsigned Sema::correctTypoInParmVarReference(
-                                    StringRef Typo,
-                                    ArrayRef<const ParmVarDecl *> ParamVars) {
-  SimpleTypoCorrector Corrector(Typo);
-  for (unsigned i = 0, e = ParamVars.size(); i != e; ++i)
-    Corrector.addDecl(ParamVars[i]);
-  if (Corrector.getBestDecl())
-    return Corrector.getBestDeclIndex();
-  else
-    return ParamCommandComment::InvalidParamIndex;
+  return ParamCommandComment::InvalidParamIndex;
 }
 
 namespace {
@@ -1079,16 +1033,18 @@ bool Sema::resolveTParamReference(
 
 namespace {
 void CorrectTypoInTParamReferenceHelper(
-                            const TemplateParameterList *TemplateParameters,
-                            SimpleTypoCorrector &Corrector) {
+    const TemplateParameterList *TemplateParameters,
+    SimpleTypoCorrection &STC) {
   for (unsigned i = 0, e = TemplateParameters->size(); i != e; ++i) {
     const NamedDecl *Param = TemplateParameters->getParam(i);
-    Corrector.addDecl(Param);
+    if (!Param)
+      continue;
+
+    STC.add(Param->getIdentifier());
 
     if (const TemplateTemplateParmDecl *TTP =
             dyn_cast<TemplateTemplateParmDecl>(Param))
-      CorrectTypoInTParamReferenceHelper(TTP->getTemplateParameters(),
-                                         Corrector);
+      CorrectTypoInTParamReferenceHelper(TTP->getTemplateParameters(), STC);
   }
 }
 } // end anonymous namespace
@@ -1096,13 +1052,12 @@ void CorrectTypoInTParamReferenceHelper(
 StringRef Sema::correctTypoInTParamReference(
                             StringRef Typo,
                             const TemplateParameterList *TemplateParameters) {
-  SimpleTypoCorrector Corrector(Typo);
-  CorrectTypoInTParamReferenceHelper(TemplateParameters, Corrector);
-  if (const NamedDecl *ND = Corrector.getBestDecl()) {
-    const IdentifierInfo *II = ND->getIdentifier();
-    assert(II && "SimpleTypoCorrector should not return this decl");
-    return II->getName();
-  }
+  SimpleTypoCorrection STC(Typo);
+  CorrectTypoInTParamReferenceHelper(TemplateParameters, STC);
+
+  if (auto CorrectedTParamReference = STC.getCorrection())
+    return *CorrectedTParamReference;
+
   return StringRef();
 }