Remove a dynamically-dead diagnostic

Author: DougGregor

include/swift/AST/DiagnosticsParse.def

@@ -648,8 +648,6 @@ ERROR(protocol_init_argument_init,none,
       "default argument not permitted in a protocol initializer", ())
 
 // Protocol Types
-ERROR(expected_langle_protocol,PointsToFirstBadToken,
-      "expected '<' in protocol composition type", ())
 ERROR(expected_rangle_protocol,PointsToFirstBadToken,
       "expected '>' to complete protocol composition type", ())
 ERROR(disallowed_protocol_composition,PointsToFirstBadToken,

lib/Parse/ParseType.cpp

@@ -410,12 +410,6 @@ ParserResult<TypeRepr> Parser::parseTypeIdentifierOrTypeComposition() {
   // Handle deprecated case
   if (Tok.getKind() == tok::kw_protocol && startsWithLess(peekToken())) {
     SourceLoc ProtocolLoc = consumeToken(tok::kw_protocol);
-    
-    // Check for the starting '<'.
-    if (!startsWithLess(Tok)) {
-      diagnose(Tok, diag::expected_langle_protocol);
-      return nullptr;
-    }
     SourceLoc LAngleLoc = consumeStartingLess();
 
     // Check for empty protocol composition.