Fix unique symbol declaration emit and add baseline test

src/compiler/transformers/declarations.ts

@@ -203,6 +203,7 @@ import {
     tryCast,
     TypeAliasDeclaration,
     TypeNode,
+    TypeOperatorNode,
     TypeParameterDeclaration,
     TypeReferenceNode,
     unescapeLeadingUnderscores,
@@ -1479,7 +1480,10 @@ export function transformDeclarations(context: TransformationContext): Transform
                             exportMappings.push([name, nameStr]);
                         }
                         const varDecl = factory.createVariableDeclaration(name, /*exclamationToken*/ undefined, type, /*initializer*/ undefined);
-                        return factory.createVariableStatement(isNonContextualKeywordName ? undefined : [factory.createToken(SyntaxKind.ExportKeyword)], factory.createVariableDeclarationList([varDecl]));
+                        const modifiers = isNonContextualKeywordName ? undefined : [factory.createToken(SyntaxKind.ExportKeyword)];
+                        const isConst = isUniqueSymbolType(type);
+                        const variableDeclarationList = factory.createVariableDeclarationList([varDecl], isConst ? NodeFlags.Const : NodeFlags.None);
+                        return factory.createVariableStatement(modifiers, variableDeclarationList);
                     });
                     if (!exportMappings.length) {
                         declarations = mapDefined(declarations, declaration => factory.replaceModifiers(declaration, ModifierFlags.None));
@@ -1817,6 +1821,13 @@ export function transformDeclarations(context: TransformationContext): Transform
         return isExportAssignment(node) || isExportDeclaration(node);
     }
 
+    function isUniqueSymbolType(type: TypeNode | undefined): boolean {
+        return !!type &&
+            type.kind === SyntaxKind.TypeOperator &&
+            (type as TypeOperatorNode).operator === SyntaxKind.UniqueKeyword &&
+            (type as TypeOperatorNode).type.kind === SyntaxKind.SymbolKeyword;
+    }
+
     function hasScopeMarker(statements: readonly Statement[]) {
         return some(statements, isScopeMarker);
     }

tests/baselines/reference/uniqueSymbolReassignment.errors.txt

@@ -0,0 +1,48 @@
+uniqueSymbolReassignment.ts(2,18): error TS2585: 'Symbol' only refers to a type, but is being used as a value here. Do you need to change your target library? Try changing the 'lib' compiler option to es2015 or later.
+uniqueSymbolReassignment.ts(7,23): error TS2585: 'Symbol' only refers to a type, but is being used as a value here. Do you need to change your target library? Try changing the 'lib' compiler option to es2015 or later.
+uniqueSymbolReassignment.ts(19,26): error TS2585: 'Symbol' only refers to a type, but is being used as a value here. Do you need to change your target library? Try changing the 'lib' compiler option to es2015 or later.
+uniqueSymbolReassignment.ts(20,26): error TS2585: 'Symbol' only refers to a type, but is being used as a value here. Do you need to change your target library? Try changing the 'lib' compiler option to es2015 or later.
+
+
+==== uniqueSymbolReassignment.ts (4 errors) ====
+    // This is a unique symbol (const + Symbol())
+    const mySymbol = Symbol('Symbols.mySymbol');
+                     ~~~~~~
+!!! error TS2585: 'Symbol' only refers to a type, but is being used as a value here. Do you need to change your target library? Try changing the 'lib' compiler option to es2015 or later.
+    const Symbols = {
+        mySymbol
+    } as const;
+
+    const anotherUnique = Symbol('symbols.anotherUnique');
+                          ~~~~~~
+!!! error TS2585: 'Symbol' only refers to a type, but is being used as a value here. Do you need to change your target library? Try changing the 'lib' compiler option to es2015 or later.
+    const Symbols2 = {
+        anotherUnique
+    } as const;
+
+    function myFunction() {}
+
+    // Attach the unique ones
+    myFunction.mySymbol = Symbols.mySymbol;
+    myFunction.anotherUnique = Symbols2.anotherUnique;
+
+    // Non-unique symbols (regular Symbol() without const)
+    const nonUniqueSymbol1 = Symbol('nonUnique1');
+                             ~~~~~~
+!!! error TS2585: 'Symbol' only refers to a type, but is being used as a value here. Do you need to change your target library? Try changing the 'lib' compiler option to es2015 or later.
+    const nonUniqueSymbol2 = Symbol('nonUnique2');
+                             ~~~~~~
+!!! error TS2585: 'Symbol' only refers to a type, but is being used as a value here. Do you need to change your target library? Try changing the 'lib' compiler option to es2015 or later.
+
+    // Plain text variables (not symbols at all)
+    const normalVar = "not a symbol";
+    const symbolName = "this contains symbol but is not one";
+
+    // Attach those as well
+    myFunction.nonUnique1 = nonUniqueSymbol1;
+    myFunction.nonUnique2 = nonUniqueSymbol2;
+    myFunction.normalVar = normalVar;
+    myFunction.symbolName = symbolName;
+
+    export { myFunction };
+

tests/baselines/reference/uniqueSymbolReassignment.js

@@ -0,0 +1,65 @@
+//// [tests/cases/compiler/uniqueSymbolReassignment.ts] ////
+
+//// [uniqueSymbolReassignment.ts]
+// This is a unique symbol (const + Symbol())
+const mySymbol = Symbol('Symbols.mySymbol');
+const Symbols = {
+    mySymbol
+} as const;
+
+const anotherUnique = Symbol('symbols.anotherUnique');
+const Symbols2 = {
+    anotherUnique
+} as const;
+
+function myFunction() {}
+
+// Attach the unique ones
+myFunction.mySymbol = Symbols.mySymbol;
+myFunction.anotherUnique = Symbols2.anotherUnique;
+
+// Non-unique symbols (regular Symbol() without const)
+const nonUniqueSymbol1 = Symbol('nonUnique1');
+const nonUniqueSymbol2 = Symbol('nonUnique2');
+
+// Plain text variables (not symbols at all)
+const normalVar = "not a symbol";
+const symbolName = "this contains symbol but is not one";
+
+// Attach those as well
+myFunction.nonUnique1 = nonUniqueSymbol1;
+myFunction.nonUnique2 = nonUniqueSymbol2;
+myFunction.normalVar = normalVar;
+myFunction.symbolName = symbolName;
+
+export { myFunction };
+
+
+//// [uniqueSymbolReassignment.js]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.myFunction = myFunction;
+// This is a unique symbol (const + Symbol())
+var mySymbol = Symbol('Symbols.mySymbol');
+var Symbols = {
+    mySymbol: mySymbol
+};
+var anotherUnique = Symbol('symbols.anotherUnique');
+var Symbols2 = {
+    anotherUnique: anotherUnique
+};
+function myFunction() { }
+// Attach the unique ones
+myFunction.mySymbol = Symbols.mySymbol;
+myFunction.anotherUnique = Symbols2.anotherUnique;
+// Non-unique symbols (regular Symbol() without const)
+var nonUniqueSymbol1 = Symbol('nonUnique1');
+var nonUniqueSymbol2 = Symbol('nonUnique2');
+// Plain text variables (not symbols at all)
+var normalVar = "not a symbol";
+var symbolName = "this contains symbol but is not one";
+// Attach those as well
+myFunction.nonUnique1 = nonUniqueSymbol1;
+myFunction.nonUnique2 = nonUniqueSymbol2;
+myFunction.normalVar = normalVar;
+myFunction.symbolName = symbolName;

tests/baselines/reference/uniqueSymbolReassignment.symbols

@@ -0,0 +1,90 @@
+//// [tests/cases/compiler/uniqueSymbolReassignment.ts] ////
+
+=== uniqueSymbolReassignment.ts ===
+// This is a unique symbol (const + Symbol())
+const mySymbol = Symbol('Symbols.mySymbol');
+>mySymbol : Symbol(mySymbol, Decl(uniqueSymbolReassignment.ts, 1, 5))
+
+const Symbols = {
+>Symbols : Symbol(Symbols, Decl(uniqueSymbolReassignment.ts, 2, 5))
+
+    mySymbol
+>mySymbol : Symbol(mySymbol, Decl(uniqueSymbolReassignment.ts, 2, 17))
+
+} as const;
+>const : Symbol(const)
+
+const anotherUnique = Symbol('symbols.anotherUnique');
+>anotherUnique : Symbol(anotherUnique, Decl(uniqueSymbolReassignment.ts, 6, 5))
+
+const Symbols2 = {
+>Symbols2 : Symbol(Symbols2, Decl(uniqueSymbolReassignment.ts, 7, 5))
+
+    anotherUnique
+>anotherUnique : Symbol(anotherUnique, Decl(uniqueSymbolReassignment.ts, 7, 18))
+
+} as const;
+>const : Symbol(const)
+
+function myFunction() {}
+>myFunction : Symbol(myFunction, Decl(uniqueSymbolReassignment.ts, 9, 11), Decl(uniqueSymbolReassignment.ts, 11, 24), Decl(uniqueSymbolReassignment.ts, 14, 39), Decl(uniqueSymbolReassignment.ts, 23, 57), Decl(uniqueSymbolReassignment.ts, 26, 41) ... and 2 more)
+
+// Attach the unique ones
+myFunction.mySymbol = Symbols.mySymbol;
+>myFunction.mySymbol : Symbol(myFunction.mySymbol, Decl(uniqueSymbolReassignment.ts, 11, 24))
+>myFunction : Symbol(myFunction, Decl(uniqueSymbolReassignment.ts, 9, 11), Decl(uniqueSymbolReassignment.ts, 11, 24), Decl(uniqueSymbolReassignment.ts, 14, 39), Decl(uniqueSymbolReassignment.ts, 23, 57), Decl(uniqueSymbolReassignment.ts, 26, 41) ... and 2 more)
+>mySymbol : Symbol(myFunction.mySymbol, Decl(uniqueSymbolReassignment.ts, 11, 24))
+>Symbols.mySymbol : Symbol(mySymbol, Decl(uniqueSymbolReassignment.ts, 2, 17))
+>Symbols : Symbol(Symbols, Decl(uniqueSymbolReassignment.ts, 2, 5))
+>mySymbol : Symbol(mySymbol, Decl(uniqueSymbolReassignment.ts, 2, 17))
+
+myFunction.anotherUnique = Symbols2.anotherUnique;
+>myFunction.anotherUnique : Symbol(myFunction.anotherUnique, Decl(uniqueSymbolReassignment.ts, 14, 39))
+>myFunction : Symbol(myFunction, Decl(uniqueSymbolReassignment.ts, 9, 11), Decl(uniqueSymbolReassignment.ts, 11, 24), Decl(uniqueSymbolReassignment.ts, 14, 39), Decl(uniqueSymbolReassignment.ts, 23, 57), Decl(uniqueSymbolReassignment.ts, 26, 41) ... and 2 more)
+>anotherUnique : Symbol(myFunction.anotherUnique, Decl(uniqueSymbolReassignment.ts, 14, 39))
+>Symbols2.anotherUnique : Symbol(anotherUnique, Decl(uniqueSymbolReassignment.ts, 7, 18))
+>Symbols2 : Symbol(Symbols2, Decl(uniqueSymbolReassignment.ts, 7, 5))
+>anotherUnique : Symbol(anotherUnique, Decl(uniqueSymbolReassignment.ts, 7, 18))
+
+// Non-unique symbols (regular Symbol() without const)
+const nonUniqueSymbol1 = Symbol('nonUnique1');
+>nonUniqueSymbol1 : Symbol(nonUniqueSymbol1, Decl(uniqueSymbolReassignment.ts, 18, 5))
+
+const nonUniqueSymbol2 = Symbol('nonUnique2');
+>nonUniqueSymbol2 : Symbol(nonUniqueSymbol2, Decl(uniqueSymbolReassignment.ts, 19, 5))
+
+// Plain text variables (not symbols at all)
+const normalVar = "not a symbol";
+>normalVar : Symbol(normalVar, Decl(uniqueSymbolReassignment.ts, 22, 5))
+
+const symbolName = "this contains symbol but is not one";
+>symbolName : Symbol(symbolName, Decl(uniqueSymbolReassignment.ts, 23, 5))
+
+// Attach those as well
+myFunction.nonUnique1 = nonUniqueSymbol1;
+>myFunction.nonUnique1 : Symbol(myFunction.nonUnique1, Decl(uniqueSymbolReassignment.ts, 23, 57))
+>myFunction : Symbol(myFunction, Decl(uniqueSymbolReassignment.ts, 9, 11), Decl(uniqueSymbolReassignment.ts, 11, 24), Decl(uniqueSymbolReassignment.ts, 14, 39), Decl(uniqueSymbolReassignment.ts, 23, 57), Decl(uniqueSymbolReassignment.ts, 26, 41) ... and 2 more)
+>nonUnique1 : Symbol(myFunction.nonUnique1, Decl(uniqueSymbolReassignment.ts, 23, 57))
+>nonUniqueSymbol1 : Symbol(nonUniqueSymbol1, Decl(uniqueSymbolReassignment.ts, 18, 5))
+
+myFunction.nonUnique2 = nonUniqueSymbol2;
+>myFunction.nonUnique2 : Symbol(myFunction.nonUnique2, Decl(uniqueSymbolReassignment.ts, 26, 41))
+>myFunction : Symbol(myFunction, Decl(uniqueSymbolReassignment.ts, 9, 11), Decl(uniqueSymbolReassignment.ts, 11, 24), Decl(uniqueSymbolReassignment.ts, 14, 39), Decl(uniqueSymbolReassignment.ts, 23, 57), Decl(uniqueSymbolReassignment.ts, 26, 41) ... and 2 more)
+>nonUnique2 : Symbol(myFunction.nonUnique2, Decl(uniqueSymbolReassignment.ts, 26, 41))
+>nonUniqueSymbol2 : Symbol(nonUniqueSymbol2, Decl(uniqueSymbolReassignment.ts, 19, 5))
+
+myFunction.normalVar = normalVar;
+>myFunction.normalVar : Symbol(myFunction.normalVar, Decl(uniqueSymbolReassignment.ts, 27, 41))
+>myFunction : Symbol(myFunction, Decl(uniqueSymbolReassignment.ts, 9, 11), Decl(uniqueSymbolReassignment.ts, 11, 24), Decl(uniqueSymbolReassignment.ts, 14, 39), Decl(uniqueSymbolReassignment.ts, 23, 57), Decl(uniqueSymbolReassignment.ts, 26, 41) ... and 2 more)
+>normalVar : Symbol(myFunction.normalVar, Decl(uniqueSymbolReassignment.ts, 27, 41))
+>normalVar : Symbol(normalVar, Decl(uniqueSymbolReassignment.ts, 22, 5))
+
+myFunction.symbolName = symbolName;
+>myFunction.symbolName : Symbol(myFunction.symbolName, Decl(uniqueSymbolReassignment.ts, 28, 33))
+>myFunction : Symbol(myFunction, Decl(uniqueSymbolReassignment.ts, 9, 11), Decl(uniqueSymbolReassignment.ts, 11, 24), Decl(uniqueSymbolReassignment.ts, 14, 39), Decl(uniqueSymbolReassignment.ts, 23, 57), Decl(uniqueSymbolReassignment.ts, 26, 41) ... and 2 more)
+>symbolName : Symbol(myFunction.symbolName, Decl(uniqueSymbolReassignment.ts, 28, 33))
+>symbolName : Symbol(symbolName, Decl(uniqueSymbolReassignment.ts, 23, 5))
+
+export { myFunction };
+>myFunction : Symbol(myFunction, Decl(uniqueSymbolReassignment.ts, 31, 8))
+