Fix support for trailing commas in tuples within generic arguments

Author: calda

lib/Parse/ParseType.cpp

@@ -1967,7 +1967,7 @@ bool Parser::canParseTypeTupleBody() {
           skipSingle();
         }
       }
-    } while (consumeIf(tok::comma));
+    } while (consumeIf(tok::comma) && Tok.isNot(tok::r_paren));
   }
 
   return consumeIf(tok::r_paren);

test/type/types.swift

@@ -234,3 +234,19 @@ let closureTypeWithTrailingCommas: (
   bar: String,
   quux: String,
 )
+
+let _ = Array<(
+  foo: Int,
+  bar: String,
+)>()
+
+let _ = Dictionary<
+  String,
+  Dictionary<
+    String,
+    Array<(
+      foo: Int,
+      bar: String,
+    )>,
+  >,
+>()