[Parser] Improve diagnostics for special platforms in available attribute.

This patch adds warnings when a version number is used
on the non-specific '*' platform. In addition, it fixes
some misleading warning messages on 'swift' platform.

Resolves: SR-8598.

Author: dingobye

include/swift/AST/DiagnosticsParse.def

@@ -1328,6 +1328,20 @@ ERROR(attr_availability_expected_equal,none,
 ERROR(attr_availability_expected_version,none,
       "expected version number in '%0' attribute", (StringRef))
 
+WARNING(attr_availability_swift_platform_expected_option,none,
+      "expected '%0' option with a version number for swift platform, "
+      "such as 'introduced', 'deprecated', or 'obsoleted'", (StringRef))
+WARNING(attr_availability_swift_platform_deprecated,none,
+      "'deprecated' must have a version number for swift platform in '%0' "
+      "attribute", (StringRef))
+WARNING(attr_availability_swift_platform_infeasible,none,
+      "argument '%0' is infeasible for swift platform in '%1' attribute",
+      (StringRef, StringRef))
+
+WARNING(attr_availability_nonspecific_platform_unexpected_version,none,
+      "unexpected version number for non-specific platform '*' in '%0' "
+      "attribute", (StringRef))
+
 // autoclosure
 ERROR(attr_autoclosure_expected_r_paren,PointsToFirstBadToken,
       "expected ')' in @autoclosure", ())

lib/Parse/ParseDecl.cpp

@@ -511,10 +511,29 @@ ParserResult<AvailableAttr> Parser::parseExtendedAvailabilitySpecList(
   bool SomeVersion = (!Introduced.empty() ||
                       !Deprecated.empty() ||
                       !Obsoleted.empty());
-  if (!PlatformKind.hasValue() &&
-      Platform == "swift" &&
-      SomeVersion &&
-      PlatformAgnostic == PlatformAgnosticAvailabilityKind::None) {
+  if (!PlatformKind.hasValue() && Platform == "swift") {
+    if (PlatformAgnostic == PlatformAgnosticAvailabilityKind::Deprecated) {
+      diagnose(AttrLoc,
+               diag::attr_availability_swift_platform_deprecated,
+               AttrName);
+      return nullptr;
+    }
+    if (PlatformAgnostic == PlatformAgnosticAvailabilityKind::Unavailable) {
+      diagnose(AttrLoc,
+               diag::attr_availability_swift_platform_infeasible,
+               "unavailable",
+               AttrName);
+      return nullptr;
+    }
+    assert(PlatformAgnostic == PlatformAgnosticAvailabilityKind::None);
+
+    if (!SomeVersion) {
+      diagnose(AttrLoc,
+               diag::attr_availability_swift_platform_expected_option,
+               AttrName);
+      return nullptr;
+    }
+
     PlatformKind = PlatformKind::none;
     PlatformAgnostic = PlatformAgnosticAvailabilityKind::SwiftVersionSpecific;
   }
@@ -528,6 +547,14 @@ ParserResult<AvailableAttr> Parser::parseExtendedAvailabilitySpecList(
     return nullptr;
   }
 
+  // Warn if any version is specified for non-specific '*' platforms.
+  if (Platform == "*" && SomeVersion) {
+    diagnose(AttrLoc,
+             diag::attr_availability_nonspecific_platform_unexpected_version,
+             AttrName);
+    return nullptr;
+  }
+
   auto Attr = new (Context)
   AvailableAttr(AtLoc, SourceRange(AttrLoc, Tok.getLoc()),
                 PlatformKind.getValue(),

test/Parse/diagnose_availability.swift

@@ -26,3 +26,35 @@ func availableOnMultiplePlatforms() {}
 // expected-error@-1 {{'deprecated' can't be combined with shorthand specification 'OSX 10.0'}}
 // expected-error@-2 {{expected declaration}}
 func twoShorthandsFollowedByDeprecated() {}
+
+
+// SR-8598: Missing/wrong warning message for '*' or 'swift' platform.
+
+@available(*, deprecated: 4.2)
+// expected-warning@-1 {{unexpected version number for non-specific platform '*' in 'available' attribute}}
+func allPlatformsDeprecatedVersion() {}
+
+@available(*, deprecated, obsoleted: 4.2)
+// expected-warning@-1 {{unexpected version number for non-specific platform '*' in 'available' attribute}}
+func allPlatformsDeprecatedAndObsoleted() {}
+
+@available(swift, unavailable)
+// expected-warning@-1 {{argument 'unavailable' is infeasible for swift platform in 'available' attribute}}
+func swiftUnavailable() {}
+
+@available(swift, unavailable, introduced: 4.2)
+// expected-warning@-1 {{argument 'unavailable' is infeasible for swift platform in 'available' attribute}}
+func swiftUnavailableIntroduced() {}
+
+@available(swift, deprecated)
+// expected-warning@-1 {{'deprecated' must have a version number for swift platform in 'available' attribute}}
+func swiftDeprecated() {}
+
+@available(swift, deprecated, obsoleted: 4.2)
+// expected-warning@-1 {{'deprecated' must have a version number for swift platform in 'available' attribute}}
+func swiftDeprecatedObsoleted() {}
+
+@available(swift, message: "missing valid option")
+// expected-warning@-1 {{expected 'available' option with a version number for swift platform, such as 'introduced', 'deprecated', or 'obsoleted'}}
+func swiftMessage() {}
+