Fix: arrow function scope strictness (take 2) (#52)

* Fix: Arrow function scope strictness (fixes #49) (#50)

* Fix: Error on functions with non-block body

* Apply suggestion from review

Co-authored-by: Toru Nagashima <[email protected]>

Author: 2 people

lib/scope.js

@@ -49,11 +49,6 @@ function isStrictScope(scope, block, isMethodDefinition, useDirective) {
         return true;
     }
 
-    // ArrowFunctionExpression's scope is always strict scope.
-    if (block.type === Syntax.ArrowFunctionExpression) {
-        return true;
-    }
-
     if (isMethodDefinition) {
         return true;
     }
@@ -67,6 +62,10 @@ function isStrictScope(scope, block, isMethodDefinition, useDirective) {
     }
 
     if (scope.type === "function") {
+        if (block.type === Syntax.ArrowFunctionExpression && block.body.type !== Syntax.BlockStatement) {
+            return false;
+        }
+
         if (block.type === Syntax.Program) {
             body = block;
         } else {

tests/es6-arrow-function-expression.js

@@ -52,7 +52,7 @@ describe("ES6 arrow function expression", () => {
         scope = scopeManager.scopes[1];
         expect(scope.type).to.be.equal("function");
         expect(scope.block.type).to.be.equal("ArrowFunctionExpression");
-        expect(scope.isStrict).to.be.true;
+        expect(scope.isStrict).to.be.false;
         expect(scope.variables).to.have.length(2);
 
         // There's no "arguments"
@@ -77,7 +77,7 @@ describe("ES6 arrow function expression", () => {
         scope = scopeManager.scopes[1];
         expect(scope.type).to.be.equal("function");
         expect(scope.block.type).to.be.equal("ArrowFunctionExpression");
-        expect(scope.isStrict).to.be.true;
+        expect(scope.isStrict).to.be.false;
         expect(scope.variables).to.have.length(4);
 
         // There's no "arguments"
@@ -86,6 +86,72 @@ describe("ES6 arrow function expression", () => {
         expect(scope.variables[2].name).to.be.equal("c");
         expect(scope.variables[3].name).to.be.equal("d");
     });
+
+    it("inherits upper scope strictness", () => {
+        const ast = espree(`
+            "use strict";
+            var arrow = () => {};
+        `);
+
+        const scopeManager = analyze(ast, { ecmaVersion: 6 });
+
+        expect(scopeManager.scopes).to.have.length(2);
+
+        let scope = scopeManager.scopes[0];
+
+        expect(scope.type).to.be.equal("global");
+        expect(scope.block.type).to.be.equal("Program");
+        expect(scope.isStrict).to.be.true;
+        expect(scope.variables).to.have.length(1);
+
+        scope = scopeManager.scopes[1];
+
+        expect(scope.type).to.be.equal("function");
+        expect(scope.block.type).to.be.equal("ArrowFunctionExpression");
+        expect(scope.isStrict).to.be.true;
+        expect(scope.variables).to.have.length(0);
+    });
+
+    it("is strict when a strictness directive is used", () => {
+        const ast = espree(`
+            var arrow = () => {
+                "use strict";
+            };
+        `);
+
+        const scopeManager = analyze(ast, { ecmaVersion: 6 });
+
+        expect(scopeManager.scopes).to.have.length(2);
+
+        let scope = scopeManager.scopes[0];
+
+        expect(scope.type).to.be.equal("global");
+        expect(scope.block.type).to.be.equal("Program");
+        expect(scope.isStrict).to.be.false;
+        expect(scope.variables).to.have.length(1);
+
+        scope = scopeManager.scopes[1];
+
+        expect(scope.type).to.be.equal("function");
+        expect(scope.block.type).to.be.equal("ArrowFunctionExpression");
+        expect(scope.isStrict).to.be.true;
+        expect(scope.variables).to.have.length(0);
+    });
+
+    it("works with no body", () => {
+        const ast = espree("var arrow = a => a;");
+
+        const scopeManager = analyze(ast, { ecmaVersion: 6 });
+
+        expect(scopeManager.scopes).to.have.length(2);
+
+        const scope = scopeManager.scopes[1];
+
+        expect(scope.type).to.be.equal("function");
+        expect(scope.block.type).to.be.equal("ArrowFunctionExpression");
+        expect(scope.isStrict).to.be.false;
+        expect(scope.variables).to.have.length(1);
+    });
 });
 
 // vim: set sw=4 ts=4 et tw=80 :