[parser] Fix scope handling of Flow declared functions (#12735)

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

@@ -5,26 +5,27 @@
 // Error messages are colocated with the plugin.
 /* eslint-disable @babel/development-internal/dry-error-messages */
 
-import type Parser from "../parser";
+import type Parser from "../../parser";
-import { types as tt, type TokenType } from "../tokenizer/types";
+import { types as tt, type TokenType } from "../../tokenizer/types";
-import * as N from "../types";
+import * as N from "../../types";
-import type { Options } from "../options";
+import type { Pos, Position } from "../../util/location";
-import type { Pos, Position } from "../util/location";
+import type State from "../../tokenizer/state";
-import type State from "../tokenizer/state";
+import { types as tc } from "../../tokenizer/context";
-import { types as tc } from "../tokenizer/context";
 import * as charCodes from "charcodes";
-import { isIteratorStart, isKeyword } from "../util/identifier";
+import { isIteratorStart, isKeyword } from "../../util/identifier";
+import FlowScopeHandler from "./scope";
 import {
   type BindingTypes,
   BIND_LEXICAL,
   BIND_VAR,
   BIND_FUNCTION,
+  BIND_FLOW_DECLARE_FN,
   SCOPE_ARROW,
   SCOPE_FUNCTION,
   SCOPE_OTHER,
-} from "../util/scopeflags";
+} from "../../util/scopeflags";
-import type { ExpressionErrors } from "../parser/util";
+import type { ExpressionErrors } from "../../parser/util";
-import { Errors } from "../parser/error";
+import { Errors } from "../../parser/error";
 
 const reservedTypes = new Set([
   "_",
@@ -185,11 +186,10 @@ export default (superClass: Class<Parser>): Class<Parser> =>
     // The value of the @flow/@noflow pragma. Initially undefined, transitions
     // to "@flow" or "@noflow" if we see a pragma. Transitions to null if we are
     // past the initial comment.
-    flowPragma: void | null | "flow" | "noflow";
+    flowPragma: void | null | "flow" | "noflow" = undefined;
 
-    constructor(options: ?Options, input: string) {
+    getScopeHandler(): Class<FlowScopeHandler> {
-      super(options, input);
+      return FlowScopeHandler;
-      this.flowPragma = undefined;
     }
 
     shouldParseTypes(): boolean {
@@ -327,6 +327,8 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       this.resetEndLocation(id);
       this.semicolon();
 
+      this.scope.declareName(node.id.name, BIND_FLOW_DECLARE_FN, node.id.start);
+
       return this.finishNode(node, "DeclareFunction");
     }
 

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

@@ -0,0 +1,56 @@
+// @flow
+
+import ScopeHandler, { Scope } from "../../util/scope";
+import {
+  BIND_FLAGS_FLOW_DECLARE_FN,
+  type ScopeFlags,
+  type BindingTypes,
+} from "../../util/scopeflags";
+import * as N from "../../types";
+
+// Reference implementation: https://github.com/facebook/flow/blob/23aeb2a2ef6eb4241ce178fde5d8f17c5f747fb5/src/typing/env.ml#L536-L584
+class FlowScope extends Scope {
+  // declare function foo(): type;
+  declareFunctions: string[] = [];
+}
+
+export default class FlowScopeHandler extends ScopeHandler<FlowScope> {
+  createScope(flags: ScopeFlags): FlowScope {
+    return new FlowScope(flags);
+  }
+
+  declareName(name: string, bindingType: BindingTypes, pos: number) {
+    const scope = this.currentScope();
+    if (bindingType & BIND_FLAGS_FLOW_DECLARE_FN) {
+      this.checkRedeclarationInScope(scope, name, bindingType, pos);
+      this.maybeExportDefined(scope, name);
+      scope.declareFunctions.push(name);
+      return;
+    }
+
+    super.declareName(...arguments);
+  }
+
+  isRedeclaredInScope(
+    scope: FlowScope,
+    name: string,
+    bindingType: BindingTypes,
+  ): boolean {
+    if (super.isRedeclaredInScope(...arguments)) return true;
+
+    if (bindingType & BIND_FLAGS_FLOW_DECLARE_FN) {
+      return (
+        !scope.declareFunctions.includes(name) &&
+        (scope.lexical.includes(name) || scope.functions.includes(name))
+      );
+    }
+
+    return false;
+  }
+
+  checkLocalExport(id: N.Identifier) {
+    if (this.scopeStack[0].declareFunctions.indexOf(id.name) === -1) {
+      super.checkLocalExport(id);
+    }
+  }
+}

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

@@ -28,20 +28,21 @@ export type ScopeFlags =
 
 // These flags are meant to be _only_ used inside the Scope class (or subclasses).
 // prettier-ignore
-export const BIND_KIND_VALUE           = 0b00000_0000_01,
+export const BIND_KIND_VALUE            = 0b000000_0000_01,
-             BIND_KIND_TYPE            = 0b00000_0000_10,
+             BIND_KIND_TYPE             = 0b000000_0000_10,
              // Used in checkLVal and declareName to determine the type of a binding
-             BIND_SCOPE_VAR            = 0b00000_0001_00, // Var-style binding
+             BIND_SCOPE_VAR             = 0b000000_0001_00, // Var-style binding
-             BIND_SCOPE_LEXICAL        = 0b00000_0010_00, // Let- or const-style binding
+             BIND_SCOPE_LEXICAL         = 0b000000_0010_00, // Let- or const-style binding
-             BIND_SCOPE_FUNCTION       = 0b00000_0100_00, // Function declaration
+             BIND_SCOPE_FUNCTION        = 0b000000_0100_00, // Function declaration
-             BIND_SCOPE_OUTSIDE        = 0b00000_1000_00, // Special case for function names as
+             BIND_SCOPE_OUTSIDE         = 0b000000_1000_00, // Special case for function names as
                                                    // bound inside the function
              // Misc flags
-             BIND_FLAGS_NONE           = 0b00001_0000_00,
+             BIND_FLAGS_NONE            = 0b000001_0000_00,
-             BIND_FLAGS_CLASS          = 0b00010_0000_00,
+             BIND_FLAGS_CLASS           = 0b000010_0000_00,
-             BIND_FLAGS_TS_ENUM        = 0b00100_0000_00,
+             BIND_FLAGS_TS_ENUM         = 0b000100_0000_00,
-             BIND_FLAGS_TS_CONST_ENUM  = 0b01000_0000_00,
+             BIND_FLAGS_TS_CONST_ENUM   = 0b001000_0000_00,
-             BIND_FLAGS_TS_EXPORT_ONLY = 0b10000_0000_00;
+             BIND_FLAGS_TS_EXPORT_ONLY  = 0b010000_0000_00,
+             BIND_FLAGS_FLOW_DECLARE_FN = 0b100000_0000_00;
 
 // These flags are meant to be _only_ used by Scope consumers
 // prettier-ignore
@@ -60,7 +61,9 @@ export const BIND_CLASS         = BIND_KIND_VALUE | BIND_KIND_TYPE | BIND_SCOPE_
              BIND_OUTSIDE       = BIND_KIND_VALUE | 0              | 0                   | BIND_FLAGS_NONE   ,
 
              BIND_TS_CONST_ENUM = BIND_TS_ENUM | BIND_FLAGS_TS_CONST_ENUM,
-             BIND_TS_NAMESPACE  = 0               | 0              | 0            | BIND_FLAGS_TS_EXPORT_ONLY;
+             BIND_TS_NAMESPACE  = 0               | 0              | 0            | BIND_FLAGS_TS_EXPORT_ONLY,
+
+             BIND_FLOW_DECLARE_FN = BIND_FLAGS_FLOW_DECLARE_FN;
 
 export type BindingTypes =
   | typeof BIND_NONE

packages/babel-parser/test/fixtures/flow/scope/declare-function-export/input.js

@@ -0,0 +1,2 @@
+declare function foo(): void;
+export { foo };

packages/babel-parser/test/fixtures/flow/scope/declare-function-export/output.json

@@ -0,0 +1,61 @@
+{
+  "type": "File",
+  "start":0,"end":45,"loc":{"start":{"line":1,"column":0},"end":{"line":2,"column":15}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":45,"loc":{"start":{"line":1,"column":0},"end":{"line":2,"column":15}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "DeclareFunction",
+        "start":0,"end":29,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":29}},
+        "id": {
+          "type": "Identifier",
+          "start":17,"end":28,"loc":{"start":{"line":1,"column":17},"end":{"line":1,"column":28},"identifierName":"foo"},
+          "name": "foo",
+          "typeAnnotation": {
+            "type": "TypeAnnotation",
+            "start":20,"end":28,"loc":{"start":{"line":1,"column":20},"end":{"line":1,"column":28}},
+            "typeAnnotation": {
+              "type": "FunctionTypeAnnotation",
+              "start":20,"end":28,"loc":{"start":{"line":1,"column":20},"end":{"line":1,"column":28}},
+              "typeParameters": null,
+              "params": [],
+              "rest": null,
+              "returnType": {
+                "type": "VoidTypeAnnotation",
+                "start":24,"end":28,"loc":{"start":{"line":1,"column":24},"end":{"line":1,"column":28}}
+              }
+            }
+          }
+        },
+        "predicate": null
+      },
+      {
+        "type": "ExportNamedDeclaration",
+        "start":30,"end":45,"loc":{"start":{"line":2,"column":0},"end":{"line":2,"column":15}},
+        "specifiers": [
+          {
+            "type": "ExportSpecifier",
+            "start":39,"end":42,"loc":{"start":{"line":2,"column":9},"end":{"line":2,"column":12}},
+            "local": {
+              "type": "Identifier",
+              "start":39,"end":42,"loc":{"start":{"line":2,"column":9},"end":{"line":2,"column":12},"identifierName":"foo"},
+              "name": "foo"
+            },
+            "exported": {
+              "type": "Identifier",
+              "start":39,"end":42,"loc":{"start":{"line":2,"column":9},"end":{"line":2,"column":12},"identifierName":"foo"},
+              "name": "foo"
+            }
+          }
+        ],
+        "source": null,
+        "declaration": null,
+        "exportKind": "value"
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/flow/scope/dupl-decl-func-declare-func/input.js

@@ -0,0 +1,2 @@
+function A() {}
+declare function A(): void;

packages/babel-parser/test/fixtures/flow/scope/dupl-decl-func-declare-func/output.json

@@ -0,0 +1,59 @@
+{
+  "type": "File",
+  "start":0,"end":43,"loc":{"start":{"line":1,"column":0},"end":{"line":2,"column":27}},
+  "errors": [
+    "SyntaxError: Identifier 'A' has already been declared (2:17)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":43,"loc":{"start":{"line":1,"column":0},"end":{"line":2,"column":27}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "FunctionDeclaration",
+        "start":0,"end":15,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":15}},
+        "id": {
+          "type": "Identifier",
+          "start":9,"end":10,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":10},"identifierName":"A"},
+          "name": "A"
+        },
+        "generator": false,
+        "async": false,
+        "params": [],
+        "body": {
+          "type": "BlockStatement",
+          "start":13,"end":15,"loc":{"start":{"line":1,"column":13},"end":{"line":1,"column":15}},
+          "body": [],
+          "directives": []
+        }
+      },
+      {
+        "type": "DeclareFunction",
+        "start":16,"end":43,"loc":{"start":{"line":2,"column":0},"end":{"line":2,"column":27}},
+        "id": {
+          "type": "Identifier",
+          "start":33,"end":42,"loc":{"start":{"line":2,"column":17},"end":{"line":2,"column":26},"identifierName":"A"},
+          "name": "A",
+          "typeAnnotation": {
+            "type": "TypeAnnotation",
+            "start":34,"end":42,"loc":{"start":{"line":2,"column":18},"end":{"line":2,"column":26}},
+            "typeAnnotation": {
+              "type": "FunctionTypeAnnotation",
+              "start":34,"end":42,"loc":{"start":{"line":2,"column":18},"end":{"line":2,"column":26}},
+              "typeParameters": null,
+              "params": [],
+              "rest": null,
+              "returnType": {
+                "type": "VoidTypeAnnotation",
+                "start":38,"end":42,"loc":{"start":{"line":2,"column":22},"end":{"line":2,"column":26}}
+              }
+            }
+          }
+        },
+        "predicate": null
+      }
+    ],
+    "directives": []
+  }
+}