No deduplication in union of tuple element types

Author: ahejlsberg

src/compiler/checker.ts

@@ -3119,7 +3119,7 @@ namespace ts {
         }
 
         function resolveTupleTypeMembers(type: TupleType) {
-            let arrayType = resolveStructuredTypeMembers(createArrayType(getUnionType(type.elementTypes)));
+            let arrayType = resolveStructuredTypeMembers(createArrayType(getUnionType(type.elementTypes, /*noDeduplication*/ true)));
             let members = createTupleTypeMemberSymbols(type.elementTypes);
             addInheritedMembers(members, arrayType.properties);
             setObjectTypeMembers(type, members, arrayType.callSignatures, arrayType.constructSignatures, arrayType.stringIndexType, arrayType.numberIndexType);