Disallow redeclaration of enum with const enum

packages/babel-parser/src/plugins/typescript/index.js

@@ -11,6 +11,7 @@ import {
   BIND_NONE,
   SCOPE_OTHER,
   BIND_TS_ENUM,
+  BIND_TS_CONST_ENUM,
   BIND_TS_TYPE,
   BIND_TS_INTERFACE,
   BIND_TS_FN_TYPE,
@@ -1123,7 +1124,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       node.id = this.parseIdentifier();
       this.checkLVal(
         node.id,
-        BIND_TS_ENUM,
+        isConst ? BIND_TS_CONST_ENUM : BIND_TS_ENUM,
         undefined,
         "typescript enum declaration",
       );

packages/babel-parser/src/plugins/typescript/scope.js

@@ -4,6 +4,7 @@ import ScopeHandler, { Scope } from "../../util/scope";
 import {
   BIND_KIND_TYPE,
   BIND_FLAGS_TS_ENUM,
+  BIND_FLAGS_TS_CONST_ENUM,
   BIND_FLAGS_TS_EXPORT_ONLY,
   BIND_KIND_VALUE,
   BIND_FLAGS_CLASS,
@@ -18,6 +19,9 @@ class TypeScriptScope extends Scope {
   // enums (which are also in .types)
   enums: string[] = [];
 
+  // const enums (which are also in .enums and .types)
+  constEnums: string[] = [];
+
   // classes (which are also in .lexical) and interface (which are also in .types)
   classes: string[] = [];
 
@@ -55,6 +59,7 @@ export default class TypeScriptScopeHandler extends ScopeHandler<TypeScriptScope
       scope.types.push(name);
     }
     if (bindingType & BIND_FLAGS_TS_ENUM) scope.enums.push(name);
+    if (bindingType & BIND_FLAGS_TS_CONST_ENUM) scope.constEnums.push(name);
     if (bindingType & BIND_FLAGS_CLASS) scope.classes.push(name);
   }
 
@@ -64,8 +69,14 @@ export default class TypeScriptScopeHandler extends ScopeHandler<TypeScriptScope
     bindingType: BindingTypes,
   ): boolean {
     if (scope.enums.indexOf(name) > -1) {
-      // Enums can be merged with other enums
-      return !(bindingType & BIND_FLAGS_TS_ENUM);
+      if (bindingType & BIND_FLAGS_TS_ENUM) {
+        // Enums can be merged with other enums if they are both
+        //  const or both non-const.
+        const isConst = !!(bindingType & BIND_FLAGS_TS_CONST_ENUM);
+        const wasConst = scope.constEnums.indexOf(name) > -1;
+        return isConst !== wasConst;
+      }
+      return true;
     }
     if (bindingType & BIND_FLAGS_CLASS && scope.classes.indexOf(name) > -1) {
       if (scope.lexical.indexOf(name) > -1) {

packages/babel-parser/src/util/scopeflags.js

@@ -37,37 +37,39 @@ export function functionFlags(isAsync: boolean, isGenerator: boolean) {
 
 // These flags are meant to be _only_ used inside the Scope class (or subclasses).
 // prettier-ignore
-export const BIND_KIND_VALUE           = 0b0000_0000_01,
-             BIND_KIND_TYPE            = 0b0000_0000_10,
+export const BIND_KIND_VALUE           = 0b00000_0000_01,
+             BIND_KIND_TYPE            = 0b00000_0000_10,
              // Used in checkLVal and declareName to determine the type of a binding
-             BIND_SCOPE_VAR            = 0b0000_0001_00, // Var-style binding
-             BIND_SCOPE_LEXICAL        = 0b0000_0010_00, // Let- or const-style binding
-             BIND_SCOPE_FUNCTION       = 0b0000_0100_00, // Function declaration
-             BIND_SCOPE_OUTSIDE        = 0b0000_1000_00, // Special case for function names as
+             BIND_SCOPE_VAR            = 0b00000_0001_00, // Var-style binding
+             BIND_SCOPE_LEXICAL        = 0b00000_0010_00, // Let- or const-style binding
+             BIND_SCOPE_FUNCTION       = 0b00000_0100_00, // Function declaration
+             BIND_SCOPE_OUTSIDE        = 0b00000_1000_00, // Special case for function names as
                                                    // bound inside the function
              // Misc flags
-             BIND_FLAGS_NONE           = 0b0001_0000_00,
-             BIND_FLAGS_CLASS          = 0b0010_0000_00,
-             BIND_FLAGS_TS_ENUM        = 0b0100_0000_00,
-             BIND_FLAGS_TS_EXPORT_ONLY = 0b1000_0000_00;
+             BIND_FLAGS_NONE           = 0b00001_0000_00,
+             BIND_FLAGS_CLASS          = 0b00010_0000_00,
+             BIND_FLAGS_TS_ENUM        = 0b00100_0000_00,
+             BIND_FLAGS_TS_CONST_ENUM  = 0b01000_0000_00,
+             BIND_FLAGS_TS_EXPORT_ONLY = 0b10000_0000_00;
 
 // These flags are meant to be _only_ used by Scope consumers
 // prettier-ignore
-/*                             =    is value?    |    is type?    |      scope          |    misc flags    */
-export const BIND_CLASS        = BIND_KIND_VALUE | BIND_KIND_TYPE | BIND_SCOPE_LEXICAL  | BIND_FLAGS_CLASS  ,
-             BIND_LEXICAL      = BIND_KIND_VALUE | 0              | BIND_SCOPE_LEXICAL  | 0                 ,
-             BIND_VAR          = BIND_KIND_VALUE | 0              | BIND_SCOPE_VAR      | 0                 ,
-             BIND_FUNCTION     = BIND_KIND_VALUE | 0              | BIND_SCOPE_FUNCTION | 0                 ,
-             BIND_TS_INTERFACE = 0               | BIND_KIND_TYPE | 0                   | BIND_FLAGS_CLASS  ,
-             BIND_TS_TYPE      = 0               | BIND_KIND_TYPE | 0                   | 0                 ,
-             BIND_TS_ENUM      = BIND_KIND_VALUE | BIND_KIND_TYPE | BIND_SCOPE_LEXICAL  | BIND_FLAGS_TS_ENUM,
-             BIND_TS_FN_TYPE   = 0               | 0              | 0            | BIND_FLAGS_TS_EXPORT_ONLY,
+/*                              =    is value?    |    is type?    |      scope          |    misc flags    */
+export const BIND_CLASS         = BIND_KIND_VALUE | BIND_KIND_TYPE | BIND_SCOPE_LEXICAL  | BIND_FLAGS_CLASS  ,
+             BIND_LEXICAL       = BIND_KIND_VALUE | 0              | BIND_SCOPE_LEXICAL  | 0                 ,
+             BIND_VAR           = BIND_KIND_VALUE | 0              | BIND_SCOPE_VAR      | 0                 ,
+             BIND_FUNCTION      = BIND_KIND_VALUE | 0              | BIND_SCOPE_FUNCTION | 0                 ,
+             BIND_TS_INTERFACE  = 0               | BIND_KIND_TYPE | 0                   | BIND_FLAGS_CLASS  ,
+             BIND_TS_TYPE       = 0               | BIND_KIND_TYPE | 0                   | 0                 ,
+             BIND_TS_ENUM       = BIND_KIND_VALUE | BIND_KIND_TYPE | BIND_SCOPE_LEXICAL  | BIND_FLAGS_TS_ENUM,
+             BIND_TS_FN_TYPE    = 0               | 0              | 0            | BIND_FLAGS_TS_EXPORT_ONLY,
              // These bindings don't introduce anything in the scope. They are used for assignments and
              // function expressions IDs.
-             BIND_NONE         = 0               | 0              | 0                   | BIND_FLAGS_NONE   ,
-             BIND_OUTSIDE      = BIND_KIND_VALUE | 0              | 0                   | BIND_FLAGS_NONE   ,
+             BIND_NONE          = 0               | 0              | 0                   | BIND_FLAGS_NONE   ,
+             BIND_OUTSIDE       = BIND_KIND_VALUE | 0              | 0                   | BIND_FLAGS_NONE   ,
 
-             BIND_TS_NAMESPACE = BIND_TS_FN_TYPE;
+             BIND_TS_CONST_ENUM = BIND_TS_ENUM | BIND_FLAGS_TS_CONST_ENUM,
+             BIND_TS_NAMESPACE  = BIND_TS_FN_TYPE;
 
 export type BindingTypes =
   | typeof BIND_NONE

packages/babel-parser/test/fixtures/typescript/scope/redeclaration-constenum-constenum/input.js

@@ -0,0 +1,2 @@
+const enum Foo {}
+const enum Foo {}

packages/babel-parser/test/fixtures/typescript/scope/redeclaration-constenum-constenum/output.json

@@ -0,0 +1,103 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 35,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 2,
+      "column": 17
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 35,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 2,
+        "column": 17
+      }
+    },
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "TSEnumDeclaration",
+        "start": 0,
+        "end": 17,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 17
+          }
+        },
+        "const": true,
+        "id": {
+          "type": "Identifier",
+          "start": 11,
+          "end": 14,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 11
+            },
+            "end": {
+              "line": 1,
+              "column": 14
+            },
+            "identifierName": "Foo"
+          },
+          "name": "Foo"
+        },
+        "members": []
+      },
+      {
+        "type": "TSEnumDeclaration",
+        "start": 18,
+        "end": 35,
+        "loc": {
+          "start": {
+            "line": 2,
+            "column": 0
+          },
+          "end": {
+            "line": 2,
+            "column": 17
+          }
+        },
+        "const": true,
+        "id": {
+          "type": "Identifier",
+          "start": 29,
+          "end": 32,
+          "loc": {
+            "start": {
+              "line": 2,
+              "column": 11
+            },
+            "end": {
+              "line": 2,
+              "column": 14
+            },
+            "identifierName": "Foo"
+          },
+          "name": "Foo"
+        },
+        "members": []
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/typescript/scope/redeclaration-constenum-enum/input.js

@@ -0,0 +1,2 @@
+const enum X {}
+enum X {}

packages/babel-parser/test/fixtures/typescript/scope/redeclaration-constenum-enum/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "Identifier 'X' has already been declared (2:5)"
+}

packages/babel-parser/test/fixtures/typescript/scope/redeclaration-enum-constenum/input.js

@@ -0,0 +1,2 @@
+enum X {}
+const enum X {}

packages/babel-parser/test/fixtures/typescript/scope/redeclaration-enum-constenum/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "Identifier 'X' has already been declared (2:11)"
+}