Merge pull request #29420 from Microsoft/fix29108

Remove overzealous simple relationship check for unique symbols

Author: rbuckton

src/compiler/checker.ts

@@ -11667,7 +11667,6 @@ namespace ts {
             if (s & TypeFlags.Undefined && (!strictNullChecks || t & (TypeFlags.Undefined | TypeFlags.Void))) return true;
             if (s & TypeFlags.Null && (!strictNullChecks || t & TypeFlags.Null)) return true;
             if (s & TypeFlags.Object && t & TypeFlags.NonPrimitive) return true;
-            if (s & TypeFlags.UniqueESSymbol || t & TypeFlags.UniqueESSymbol) return false;
             if (relation === assignableRelation || relation === comparableRelation) {
                 if (s & TypeFlags.Any) return true;
                 // Type number or any numeric literal type is assignable to any numeric enum type or any

tests/baselines/reference/uniqueSymbols.js

@@ -28,6 +28,10 @@ var varInitToConstDeclAmbient = constType;
 const constInitToConstCallWithTypeQuery: typeof constCall = constCall;
 const constInitToConstDeclAmbientWithTypeQuery: typeof constType = constType;
 
+// assignment from any
+// https://github.com/Microsoft/TypeScript/issues/29108
+const fromAny: unique symbol = {} as any;
+
 // function return inference
 function funcReturnConstCall() { return constCall; }
 function funcReturnLetCall() { return letCall; }
@@ -286,6 +290,9 @@ var varInitToConstDeclAmbient = constType;
 // declaration from initializer with type query
 const constInitToConstCallWithTypeQuery = constCall;
 const constInitToConstDeclAmbientWithTypeQuery = constType;
+// assignment from any
+// https://github.com/Microsoft/TypeScript/issues/29108
+const fromAny = {};
 // function return inference
 function funcReturnConstCall() { return constCall; }
 function funcReturnLetCall() { return letCall; }