Reject module selectors on SPI groups

Author: beccadax

lib/Parse/ParseDecl.cpp

@@ -687,6 +687,7 @@ bool Parser::parseSpecializeAttributeArguments(
           consumeToken();
           return false;
         }
+        diagnoseAndConsumeIfModuleSelector("SPI group");
         auto text = Tok.getText();
         spiGroups.push_back(Context.getIdentifier(text));
         consumeToken();
@@ -2974,6 +2975,8 @@ ParserStatus Parser::parseNewDeclAttribute(DeclAttributes &Attributes,
       return makeParserSuccess();
     }
 
+    diagnoseAndConsumeIfModuleSelector("SPI group");
+
     auto text = Tok.getText();
     // An spi group name can be '_' as in @_spi(_), a specifier for implicit import of the SPI.
     // '_' in source code is represented as an empty identifier in AST so match the behavior

test/NameLookup/module_selector.swift

@@ -474,8 +474,15 @@ func badModuleNames() {
   let y: A.NonexistentModule::MyChildType = fatalError()
   // expected-error@-1 {{'NonexistentModule::MyChildType' is not a member type of struct 'ModuleSelectorTestingKit.A'}}
 }
+
+@_spi(main::Private)
+// expected-error@-1 {{name of SPI group declaration cannot be qualified with module selector}} {{7-13=}}
 public struct BadImplementsAttr: CustomStringConvertible {
   @_implements(CustomStringConvertible, Swift::description)
   // expected-error@-1 {{name cannot be qualified with module selector here}} {{41-48=}}
   public var stringValue: String { fatalError() }
+
+  @_specialize(spi: main::Private, where T == Swift::Int)
+  // expected-error@-1 {{name of SPI group declaration cannot be qualified with module selector}} {{21-27=}}
+  public func fn<T>() -> T { fatalError() }
 }