Add fix-it to change @Availability to @available.

When we parse '@Availability', treat it as '@available' and emit a Fix-It to rename.

rdar://problem/20974602

Swift SVN r28771

include/swift/AST/DiagnosticsParse.def

@@ -1076,6 +1076,9 @@ ERROR(attr_availability_expected_equal,attribute_parsing,none,
 ERROR(attr_availability_expected_version,attribute_parsing,none,
       "expected version number in '%0' attribute", (StringRef))
 
+ERROR(attr_availability_renamed, attribute_parsing, none,
+      "@availability has been renamed to @available", ())
+
 // autoclosure
 ERROR(attr_autoclosure_expected_r_paren,attribute_parsing,PointsToFirstBadToken,
       "expected ')' in @autoclosure", ())

lib/Parse/ParseDecl.cpp

@@ -1247,6 +1247,15 @@ bool Parser::parseDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc) {
   // If the attribute follows the new representation, switch
   // over to the alternate parsing path.
   DeclAttrKind DK = DeclAttribute::getAttrKindFromString(Tok.getText());
+
+  if (DK == DAK_Count && Tok.getText() == "availability") {
+    // We renamed @availability to @available, so if we see the former,
+    // treat it as the latter and emit a Fix-It.
+    DK = DAK_Available;
+    diagnose(Tok, diag::attr_availability_renamed)
+        .fixItReplace(Tok.getLoc(), "available");
+  }
+
   if (DK != DAK_Count && !DeclAttribute::shouldBeRejectedByParser(DK))
     return parseNewDeclAttribute(Attributes, AtLoc, DK);
 

test/attr/attr_availability.swift

@@ -182,3 +182,6 @@ func shortFormWithWildcardInMiddle() {}
 
 @available(iOS 8.0, OSX 10.10.3) // expected-error {{must handle potential future platforms with '*'}}
 func shortFormMissingWildcard() {}
+
+@availability(OSX, introduced=10.10) // expected-error {{@availability has been renamed to @available}} {{2-14=available}}
+func someFuncUsingOldAttribute() { }