Change isolatedModules to allow const enum declaration and disallow access
Fixes #20703 with solution suggested in https://github.com/Microsoft/TypeScript/issues/20703#issuecomment-361434795 Previously, `--isolatedModules` gave an error for any ambient const enum, which meant that some third-party libraries would always give errors even if the ambient const enums they declare were never used. Now, we only give an error when an ambient const enum is referenced, which allows such libraries to still be used as long as the const enums are never accessed. Some nuances: * As before, the error is only surfaced for *ambient* const enums. With non-ambient const enums, we know that an `isolatedModules` build will emit the enum and produce a plain reference rather than inlining the constant, so everything will still work. * I originally planned to do this check in the code path that inlines the constant, but that code is only exercised at emit time, so, for example, the TS language service wasn't giving an error in my editor. Instead, I do the check at typecheck time next to another const-enum-related check. * This can be a breaking change when using `skipLibCheck` because the error is typically moved from a .d.ts file to a .ts file. Testing done: I ran this TS build on a large project of mine that previously had disabled `isolatedModules` so I could use the `chalk` library. With `isolatedModules` enabled, there was no longer an error in the chalk typedefs, and a reference to the `Level` const enum produced an error in my editor.
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7 changed files with 48 additions and 32 deletions
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@ -22567,6 +22567,12 @@ namespace ts {
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}
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if (isConstEnumObjectType(type)) {
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checkConstEnumAccess(node, type);
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}
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return type;
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}
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function checkConstEnumAccess(node: Expression | QualifiedName, type: Type) {
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// enum object type for const enums are only permitted in:
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// - 'left' in property access
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// - 'object' in indexed access
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@ -22580,8 +22586,14 @@ namespace ts {
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if (!ok) {
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error(node, Diagnostics.const_enums_can_only_be_used_in_property_or_index_access_expressions_or_the_right_hand_side_of_an_import_declaration_or_export_assignment_or_type_query);
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}
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if (compilerOptions.isolatedModules) {
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Debug.assert(!!(type.symbol.flags & SymbolFlags.ConstEnum));
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const constEnumDeclaration = type.symbol.valueDeclaration as EnumDeclaration;
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if (constEnumDeclaration.flags & NodeFlags.Ambient) {
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error(node, Diagnostics.Cannot_access_ambient_const_enums_when_the_isolatedModules_flag_is_provided);
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}
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}
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return type;
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}
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function checkParenthesizedExpression(node: ParenthesizedExpression, checkMode?: CheckMode): Type {
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@ -26721,11 +26733,6 @@ namespace ts {
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computeEnumMemberValues(node);
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const enumIsConst = isEnumConst(node);
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if (compilerOptions.isolatedModules && enumIsConst && node.flags & NodeFlags.Ambient) {
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error(node.name, Diagnostics.Ambient_const_enums_are_not_allowed_when_the_isolatedModules_flag_is_provided);
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}
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// Spec 2014 - Section 9.3:
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// It isn't possible for one enum declaration to continue the automatic numbering sequence of another,
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// and when an enum type has multiple declarations, only one declaration is permitted to omit a value
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@ -26736,6 +26743,7 @@ namespace ts {
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const firstDeclaration = getDeclarationOfKind(enumSymbol, node.kind);
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if (node === firstDeclaration) {
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if (enumSymbol.declarations.length > 1) {
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const enumIsConst = isEnumConst(node);
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// check that const is placed\omitted on all enum declarations
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forEach(enumSymbol.declarations, decl => {
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if (isEnumDeclaration(decl) && isEnumConst(decl) !== enumIsConst) {
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@ -659,10 +659,6 @@
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"category": "Error",
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"code": 1208
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},
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"Ambient const enums are not allowed when the '--isolatedModules' flag is provided.": {
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"category": "Error",
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"code": 1209
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},
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"Invalid use of '{0}'. Class definitions are automatically in strict mode.": {
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"category": "Error",
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"code": 1210
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@ -2513,6 +2509,10 @@
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"category": "Message",
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"code": 2738
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},
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"Cannot access ambient const enums when the '--isolatedModules' flag is provided.": {
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"category": "Error",
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"code": 2739
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},
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"Import declaration '{0}' is using private name '{1}'.": {
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"category": "Error",
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@ -1,8 +1,9 @@
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tests/cases/compiler/file1.ts(1,20): error TS1209: Ambient const enums are not allowed when the '--isolatedModules' flag is provided.
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tests/cases/compiler/file1.ts(2,16): error TS2739: Cannot access ambient const enums when the '--isolatedModules' flag is provided.
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==== tests/cases/compiler/file1.ts (1 errors) ====
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declare const enum E { X = 1}
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export var y = E.X;
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~
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!!! error TS1209: Ambient const enums are not allowed when the '--isolatedModules' flag is provided.
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export var y;
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!!! error TS2739: Cannot access ambient const enums when the '--isolatedModules' flag is provided.
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@ -1,6 +1,7 @@
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//// [file1.ts]
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declare const enum E { X = 1}
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export var y;
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export var y = E.X;
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//// [file1.js]
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export var y;
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export var y = E.X;
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@ -3,6 +3,9 @@ declare const enum E { X = 1}
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>E : Symbol(E, Decl(file1.ts, 0, 0))
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>X : Symbol(E.X, Decl(file1.ts, 0, 22))
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export var y;
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export var y = E.X;
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>y : Symbol(y, Decl(file1.ts, 1, 10))
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>E.X : Symbol(E.X, Decl(file1.ts, 0, 22))
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>E : Symbol(E, Decl(file1.ts, 0, 0))
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>X : Symbol(E.X, Decl(file1.ts, 0, 22))
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@ -4,6 +4,9 @@ declare const enum E { X = 1}
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>X : E.X
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>1 : 1
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export var y;
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>y : any
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export var y = E.X;
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>y : E
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>E.X : E
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>E : typeof E
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>X : E
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@ -4,4 +4,4 @@
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// @filename: file1.ts
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declare const enum E { X = 1}
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export var y;
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export var y = E.X;
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