Move getPropertyNameForUniqueESSymbol to utility

for consistency with other calculation of
special property names (starting with __),
move the calculation of property names for
unique es symbols to `utilities.ts`.

Signed-off-by: Max Heiber <[email protected]>

Author: Max Heiber

src/compiler/checker.ts

@@ -6252,7 +6252,7 @@ namespace ts {
          */
         function getLateBoundNameFromType(type: LiteralType | UniqueESSymbolType): __String {
             if (type.flags & TypeFlags.UniqueESSymbol) {
-                return `__@${type.symbol.escapedName}@${getSymbolId(type.symbol)}` as __String;
+                return getPropertyNameForUniqueESSymbol(type.symbol);
             }
             if (type.flags & (TypeFlags.StringLiteral | TypeFlags.NumberLiteral)) {
                 return escapeLeadingUnderscores("" + (<LiteralType>type).value);

src/compiler/utilities.ts

@@ -2728,6 +2728,10 @@ namespace ts {
         return node.kind === SyntaxKind.Identifier || node.kind === SyntaxKind.PrivateName ? node.escapedText : escapeLeadingUnderscores(node.text);
     }
 
+    export function getPropertyNameForUniqueESSymbol(symbol: Symbol): __String {
+        return `__@${getSymbolId(symbol)}@${symbol.escapedName}` as __String;
+    }
+
     export function getPropertyNameForKnownSymbolName(symbolName: string): __String {
         return "__@" + symbolName as __String;
     }