Parse @_implements(Proto, DeclName)

Author: graydon

include/swift/AST/DiagnosticsParse.def

@@ -1352,6 +1352,10 @@ ERROR(attr_specialize_parameter_already_defined,none,
 ERROR(attr_specialize_expected_partial_or_full,none,
       "expected 'partial' or 'full' as values of the 'kind' parameter in '_specialize' attribute", ())
 
+// _implements
+ERROR(attr_implements_expected_member_name,PointsToFirstBadToken,
+      "expected a member name as second parameter in '_implements' attribute", ())
+
 //------------------------------------------------------------------------------
 // Generics parsing diagnostics
 //------------------------------------------------------------------------------

include/swift/Parse/Parser.h

@@ -730,6 +730,11 @@ class Parser {
   bool parseSpecializeAttribute(swift::tok ClosingBrace, SourceLoc AtLoc,
                                 SourceLoc Loc, SpecializeAttr *&Attr);
 
+  /// Parse the @_implements attribute.
+  /// \p Attr is where to store the parsed attribute
+  ParserResult<ImplementsAttr> parseImplementsAttribute(SourceLoc AtLoc,
+                                                        SourceLoc Loc);
+
   /// Parse a specific attribute.
   bool parseDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc);
 

lib/Parse/ParseDecl.cpp

@@ -437,6 +437,62 @@ bool Parser::parseSpecializeAttribute(swift::tok ClosingBrace, SourceLoc AtLoc,
   return true;
 }
 
+ParserResult<ImplementsAttr>
+Parser::parseImplementsAttribute(SourceLoc AtLoc, SourceLoc Loc) {
+  StringRef AttrName = "_implements";
+  ParserStatus Status;
+
+  if (Tok.isNot(tok::l_paren)) {
+    diagnose(Loc, diag::attr_expected_lparen, AttrName,
+             /*DeclModifier=*/false);
+    Status.setIsParseError();
+    return Status;
+  }
+
+  SourceLoc lParenLoc = consumeToken();
+
+  ParserResult<TypeRepr> ProtocolType = parseType();
+  Status |= ProtocolType;
+
+  if (!(Status.shouldStopParsing() || consumeIf(tok::comma))) {
+    diagnose(Tok.getLoc(), diag::attr_expected_comma, AttrName,
+             /*DeclModifier=*/false);
+    Status.setIsParseError();
+  }
+
+  DeclNameLoc MemberNameLoc;
+  DeclName MemberName;
+  if (!Status.shouldStopParsing()) {
+    MemberName =
+      parseUnqualifiedDeclName(/*afterDot=*/false, MemberNameLoc,
+                               diag::attr_implements_expected_member_name,
+                               /*allowOperators=*/true,
+                               /*allowZeroArgCompoundNames=*/true);
+    if (!MemberName) {
+      Status.setIsParseError();
+    }
+  }
+
+  if (Status.isError()) {
+    skipUntil(tok::r_paren);
+  }
+
+  SourceLoc rParenLoc;
+  if (!consumeIf(tok::r_paren, rParenLoc)) {
+    diagnose(lParenLoc, diag::attr_expected_rparen, AttrName,
+             /*DeclModifier=*/false);
+    Status.setIsParseError();
+  }
+
+  if (Status.isError()) {
+    return Status;
+  }
+
+  return ParserResult<ImplementsAttr>(
+    ImplementsAttr::create(Context, AtLoc, SourceRange(Loc, rParenLoc),
+                           ProtocolType.get(), MemberName, MemberNameLoc));
+}
+
 bool Parser::parseNewDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc,
                                    DeclAttrKind DK) {
   // Ok, it is a valid attribute, eat it, and then process it.
@@ -1258,6 +1314,14 @@ bool Parser::parseNewDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc,
     Attributes.add(Attr);
     break;
     }
+
+  case DAK_Implements: {
+    ParserResult<ImplementsAttr> Attr = parseImplementsAttribute(AtLoc, Loc);
+    if (Attr.isNonNull()) {
+      Attributes.add(Attr.get());
+    }
+    break;
+  }
   }
 
   if (DuplicateAttribute) {