Implement typo correction for id-expressions, e.g.,

typo.cpp:22:10: error: use of undeclared identifier 'radious'; did
      you mean 'radius'?
  return radious * pi;
         ^~~~~~~
         radius

This was super-easy, since we already had decent recovery by looking
for names in dependent base classes.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@92341 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/Sema.h b/lib/Sema/Sema.h
index 06927b6..b92bd4f 100644
--- a/lib/Sema/Sema.h
+++ b/lib/Sema/Sema.h
@@ -1209,8 +1209,7 @@
                           VisibleDeclConsumer &Consumer);
 
   bool CorrectTypo(LookupResult &R, Scope *S, const CXXScopeSpec *SS,
-                        bool AllowBuiltinCreation = false,
-                        bool EnteringContext = false);
+                   bool EnteringContext = false);
 
   void FindAssociatedClassesAndNamespaces(Expr **Args, unsigned NumArgs,
                                    AssociatedNamespaceSet &AssociatedNamespaces,
@@ -1458,7 +1457,7 @@
                                              bool HasTrailingLParen,
                                              bool IsAddressOfOperand);
 
-  bool DiagnoseEmptyLookup(const CXXScopeSpec &SS, LookupResult &R);
+  bool DiagnoseEmptyLookup(Scope *S, const CXXScopeSpec &SS, LookupResult &R);
 
   OwningExprResult LookupInObjCMethod(LookupResult &R,
                                       Scope *S,
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 77ddbc2..c87a274 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -879,28 +879,25 @@
 /// Diagnose an empty lookup.
 ///
 /// \return false if new lookup candidates were found
-bool Sema::DiagnoseEmptyLookup(const CXXScopeSpec &SS,
+bool Sema::DiagnoseEmptyLookup(Scope *S, const CXXScopeSpec &SS,
                                LookupResult &R) {
   DeclarationName Name = R.getLookupName();
 
-  // We don't know how to recover from bad qualified lookups.
-  if (!SS.isEmpty()) {
-    Diag(R.getNameLoc(), diag::err_no_member)
-      << Name << computeDeclContext(SS, false)
-      << SS.getRange();
-    return true;
-  }
-
   unsigned diagnostic = diag::err_undeclared_var_use;
+  unsigned diagnostic_suggest = diag::err_undeclared_var_use_suggest;
   if (Name.getNameKind() == DeclarationName::CXXOperatorName ||
       Name.getNameKind() == DeclarationName::CXXLiteralOperatorName ||
-      Name.getNameKind() == DeclarationName::CXXConversionFunctionName)
+      Name.getNameKind() == DeclarationName::CXXConversionFunctionName) {
     diagnostic = diag::err_undeclared_use;
+    diagnostic_suggest = diag::err_undeclared_use_suggest;
+  }
 
-  // Fake an unqualified lookup.  This is useful when (for example)
-  // the original lookup would not have found something because it was
-  // a dependent name.
-  for (DeclContext *DC = CurContext; DC; DC = DC->getParent()) {
+  // If the original lookup was an unqualified lookup, fake an
+  // unqualified lookup.  This is useful when (for example) the
+  // original lookup would not have found something because it was a
+  // dependent name.
+  for (DeclContext *DC = SS.isEmpty()? CurContext : 0;
+       DC; DC = DC->getParent()) {
     if (isa<CXXRecordDecl>(DC)) {
       LookupQualifiedName(R, DC);
 
@@ -933,6 +930,33 @@
     }
   }
 
+  // We didn't find anything, so try to correct for a typo.
+  if (S && CorrectTypo(R, S, &SS) && 
+      (isa<ValueDecl>(*R.begin()) || isa<TemplateDecl>(*R.begin()))) {
+    if (SS.isEmpty())
+      Diag(R.getNameLoc(), diagnostic_suggest) << Name << R.getLookupName()
+        << CodeModificationHint::CreateReplacement(R.getNameLoc(),
+                                              R.getLookupName().getAsString());
+    else 
+      Diag(R.getNameLoc(), diag::err_no_member_suggest)
+        << Name << computeDeclContext(SS, false) << R.getLookupName()
+        << SS.getRange()
+        << CodeModificationHint::CreateReplacement(R.getNameLoc(),
+                                              R.getLookupName().getAsString());
+
+    // Tell the callee to try to recover.
+    return false;
+  }
+
+  // Emit a special diagnostic for failed member lookups.
+  // FIXME: computing the declaration context might fail here (?)
+  if (!SS.isEmpty()) {
+    Diag(R.getNameLoc(), diag::err_no_member)
+      << Name << computeDeclContext(SS, false)
+      << SS.getRange();
+    return true;
+  }
+
   // Give up, we can't recover.
   Diag(R.getNameLoc(), diagnostic) << Name;
   return true;
@@ -1010,7 +1034,7 @@
     // If this name wasn't predeclared and if this is not a function
     // call, diagnose the problem.
     if (R.empty()) {
-      if (DiagnoseEmptyLookup(SS, R))
+      if (DiagnoseEmptyLookup(S, SS, R))
         return ExprError();
 
       assert(!R.empty() &&
diff --git a/lib/Sema/SemaLookup.cpp b/lib/Sema/SemaLookup.cpp
index 72779c3..9abbd57 100644
--- a/lib/Sema/SemaLookup.cpp
+++ b/lib/Sema/SemaLookup.cpp
@@ -2134,11 +2134,14 @@
 /// \param SS the nested-name-specifier that precedes the name we're
 /// looking for, if present.
 ///
+/// \param EnteringContext whether we're entering the context described by 
+/// the nested-name-specifier SS.
+///
 /// \returns true if the typo was corrected, in which case the \p Res
 /// structure will contain the results of name lookup for the
 /// corrected name. Otherwise, returns false.
 bool Sema::CorrectTypo(LookupResult &Res, Scope *S, const CXXScopeSpec *SS,
-                       bool AllowBuiltinCreation, bool EnteringContext) {
+                       bool EnteringContext) {
   // We only attempt to correct typos for identifiers.
   IdentifierInfo *Typo = Res.getLookupName().getAsIdentifierInfo();
   if (!Typo)
@@ -2190,6 +2193,12 @@
   // success if we found something that was not ambiguous.
   Res.clear();
   Res.setLookupName(BestName);
-  LookupParsedName(Res, S, SS, AllowBuiltinCreation, EnteringContext);
-  return Res.getResultKind() != LookupResult::NotFound && !Res.isAmbiguous();
+  LookupParsedName(Res, S, SS, /*AllowBuiltinCreation=*/false, EnteringContext);
+
+  if (Res.isAmbiguous()) {
+    Res.suppressDiagnostics();
+    return false;
+  }
+
+  return Res.getResultKind() != LookupResult::NotFound;
 }
diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index 99dbaba..5892081 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -4822,7 +4822,7 @@
 
   LookupResult R(SemaRef, ULE->getName(), ULE->getNameLoc(),
                  Sema::LookupOrdinaryName);
-  if (SemaRef.DiagnoseEmptyLookup(SS, R))
+  if (SemaRef.DiagnoseEmptyLookup(/*Scope=*/0, SS, R))
     return Destroy(SemaRef, Fn, Args, NumArgs);
 
   assert(!R.empty() && "lookup results empty despite recovery");