From 40f7a007e9d06078ff49e5bcc4587150c098fb66 Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Mon, 4 Jan 2010 17:27:12 +0000
Subject: [PATCH] When declaring an Objective-C implementation without a
 corresponding interface, suggest correction of typos. For example, given:

  @interface NSString
  @end

  @implementation NSstring
  @end

we'll warn with:

t.m:4:19: warning: cannot find interface declaration for 'NSstring';
    did you mean 'NSString'?
  @implementation NSstring
                  ^

However, since this is just a warning, we don't provide a fix-it
hint. Good idea, Ted!

llvm-svn: 92488
---
 .../clang/Basic/DiagnosticSemaKinds.td        |  2 ++
 clang/lib/Sema/SemaDeclObjC.cpp               | 22 +++++++++++++++----
 clang/test/SemaObjC/undef-superclass-1.m      |  2 ++
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index fb7a6abf1043..14271c8d9072 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2575,6 +2575,8 @@ def err_property_not_found_suggest : Error<
   "property %0 not found on object of type %1; did you mean %2?">;
 def err_undef_interface_suggest : Error<
   "cannot find interface declaration for %0; did you mean %1?">;
+def warn_undef_interface_suggest : Warning<
+  "cannot find interface declaration for %0; did you mean %1?">;
 def err_undef_superclass_suggest : Error<
   "cannot find interface declaration for %0, superclass of %1; did you mean "
   "%2?">;
diff --git a/clang/lib/Sema/SemaDeclObjC.cpp b/clang/lib/Sema/SemaDeclObjC.cpp
index 6ff898970af0..fb2cc712dce9 100644
--- a/clang/lib/Sema/SemaDeclObjC.cpp
+++ b/clang/lib/Sema/SemaDeclObjC.cpp
@@ -689,13 +689,27 @@ Sema::DeclPtrTy Sema::ActOnStartClassImplementation(
   if (PrevDecl && !isa<ObjCInterfaceDecl>(PrevDecl)) {
     Diag(ClassLoc, diag::err_redefinition_different_kind) << ClassName;
     Diag(PrevDecl->getLocation(), diag::note_previous_definition);
-  }  else {
-    // Is there an interface declaration of this class; if not, warn!
-    IDecl = dyn_cast_or_null<ObjCInterfaceDecl>(PrevDecl);
-    if (!IDecl || IDecl->isForwardDecl()) {
+  } else if ((IDecl = dyn_cast_or_null<ObjCInterfaceDecl>(PrevDecl))) {
+    // If this is a forward declaration of an interface, warn.
+    if (IDecl->isForwardDecl()) {
       Diag(ClassLoc, diag::warn_undef_interface) << ClassName;
       IDecl = 0;
     }
+  } else {
+    // We did not find anything with the name ClassName; try to correct for 
+    // typos in the class name.
+    LookupResult R(*this, ClassName, ClassLoc, LookupOrdinaryName);
+    if (CorrectTypo(R, TUScope, 0) &&
+        (IDecl = R.getAsSingle<ObjCInterfaceDecl>())) {
+      // Suggest the (potentially) correct interface name. However, don't
+      // provide a code-modification hint or use the typo name for recovery,
+      // because this is just a warning. The program may actually be correct.
+      Diag(ClassLoc, diag::warn_undef_interface_suggest)
+        << ClassName << R.getLookupName();
+      IDecl = 0;
+    } else {
+      Diag(ClassLoc, diag::warn_undef_interface) << ClassName;
+    }
   }
 
   // Check that super class name is valid class name
diff --git a/clang/test/SemaObjC/undef-superclass-1.m b/clang/test/SemaObjC/undef-superclass-1.m
index 7611cf3b1554..56697e23c2b5 100644
--- a/clang/test/SemaObjC/undef-superclass-1.m
+++ b/clang/test/SemaObjC/undef-superclass-1.m
@@ -31,3 +31,5 @@
 @implementation RecursiveClass
 @end
 
+@implementation iNTF3 // expected-warning{{cannot find interface declaration for 'iNTF3'; did you mean 'INTF3'?}}
+@end