Emit unqiue symbols with typeof if possible before issuing an error (#21403)

src/compiler/checker.ts

@@ -2898,6 +2898,9 @@ namespace ts {
                 }
                 if (type.flags & TypeFlags.UniqueESSymbol) {
                     if (!(context.flags & NodeBuilderFlags.AllowUniqueESSymbolType)) {
+                        if (isValueSymbolAccessible(type.symbol, context.enclosingDeclaration)) {
+                            return createTypeQueryNode(symbolToName(type.symbol, context, SymbolFlags.Value, /*expectsIdentifier*/ false));
+                        }
                         if (context.tracker.reportInaccessibleUniqueSymbolError) {
                             context.tracker.reportInaccessibleUniqueSymbolError();
                         }

src/harness/typeWriter.ts

@@ -79,7 +79,7 @@ class TypeWriterWalker {
             // Workaround to ensure we output 'C' instead of 'typeof C' for base class expressions
             // let type = this.checker.getTypeAtLocation(node);
             const type = node.parent && ts.isExpressionWithTypeArgumentsInClassExtendsClause(node.parent) && this.checker.getTypeAtLocation(node.parent) || this.checker.getTypeAtLocation(node);
-            const typeString = type ? this.checker.typeToString(type, node.parent, ts.TypeFormatFlags.NoTruncation) : "No type information available!";
+            const typeString = type ? this.checker.typeToString(type, node.parent, ts.TypeFormatFlags.NoTruncation | ts.TypeFormatFlags.AllowUniqueESSymbolType) : "No type information available!";
             return {
                 line: lineAndCharacter.line,
                 syntaxKind: node.kind,

tests/baselines/reference/indirectUniqueSymbolDeclarationEmit.js

@@ -0,0 +1,23 @@
+//// [indirectUniqueSymbolDeclarationEmit.ts]
+export const x = Symbol();
+export const y = Symbol();
+declare function rand(): boolean;
+export function f() {
+    return rand() ? x : y;
+}
+
+//// [indirectUniqueSymbolDeclarationEmit.js]
+"use strict";
+exports.__esModule = true;
+exports.x = Symbol();
+exports.y = Symbol();
+function f() {
+    return rand() ? exports.x : exports.y;
+}
+exports.f = f;
+
+
+//// [indirectUniqueSymbolDeclarationEmit.d.ts]
+export declare const x: unique symbol;
+export declare const y: unique symbol;
+export declare function f(): typeof x | typeof y;

tests/baselines/reference/indirectUniqueSymbolDeclarationEmit.symbols

@@ -0,0 +1,20 @@
+=== tests/cases/compiler/indirectUniqueSymbolDeclarationEmit.ts ===
+export const x = Symbol();
+>x : Symbol(x, Decl(indirectUniqueSymbolDeclarationEmit.ts, 0, 12))
+>Symbol : Symbol(Symbol, Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --))
+
+export const y = Symbol();
+>y : Symbol(y, Decl(indirectUniqueSymbolDeclarationEmit.ts, 1, 12))
+>Symbol : Symbol(Symbol, Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --))
+
+declare function rand(): boolean;
+>rand : Symbol(rand, Decl(indirectUniqueSymbolDeclarationEmit.ts, 1, 26))
+
+export function f() {
+>f : Symbol(f, Decl(indirectUniqueSymbolDeclarationEmit.ts, 2, 33))
+
+    return rand() ? x : y;
+>rand : Symbol(rand, Decl(indirectUniqueSymbolDeclarationEmit.ts, 1, 26))
+>x : Symbol(x, Decl(indirectUniqueSymbolDeclarationEmit.ts, 0, 12))
+>y : Symbol(y, Decl(indirectUniqueSymbolDeclarationEmit.ts, 1, 12))
+}

tests/baselines/reference/indirectUniqueSymbolDeclarationEmit.types

@@ -0,0 +1,24 @@
+=== tests/cases/compiler/indirectUniqueSymbolDeclarationEmit.ts ===
+export const x = Symbol();
+>x : unique symbol
+>Symbol() : unique symbol
+>Symbol : SymbolConstructor
+
+export const y = Symbol();
+>y : unique symbol
+>Symbol() : unique symbol
+>Symbol : SymbolConstructor
+
+declare function rand(): boolean;
+>rand : () => boolean
+
+export function f() {
+>f : () => unique symbol | unique symbol
+
+    return rand() ? x : y;
+>rand() ? x : y : unique symbol | unique symbol
+>rand() : boolean
+>rand : () => boolean
+>x : unique symbol
+>y : unique symbol
+}

tests/cases/compiler/indirectUniqueSymbolDeclarationEmit.ts

@@ -0,0 +1,8 @@
+// @lib: es6
+// @declaration: true
+export const x = Symbol();
+export const y = Symbol();
+declare function rand(): boolean;
+export function f() {
+    return rand() ? x : y;
+}