Make getBinding ignore labels; add Scope#getLabel, Scope#registerLabel (#4758)

* Make getBinding ignore labels; add Scope#getLabel, Scope#registerLabel

* generateUid: account for labels again

packages/babel-traverse/src/scope/index.js

@@ -161,6 +161,8 @@ export default class Scope {
     this.parentBlock = path.parent;
     this.block       = path.node;
     this.path        = path;
+
+    this.labels      = new Map();
   }
 
   /**
@@ -218,7 +220,7 @@ export default class Scope {
     do {
       uid = this._generateUid(name, i);
       i++;
-    } while (this.hasBinding(uid) || this.hasGlobal(uid) || this.hasReference(uid));
+    } while (this.hasLabel(uid) || this.hasBinding(uid) || this.hasGlobal(uid) || this.hasReference(uid));
 
     let program = this.getProgramParent();
     program.references[uid] = true;
@@ -426,9 +428,21 @@ export default class Scope {
     return t.callExpression(file.addHelper(helperName), args);
   }
 
+  hasLabel(name: string) {
+    return !!this.getLabel(name);
+  }
+
+  getLabel(name: string) {
+    return this.labels.get(name);
+  }
+
+  registerLabel(path: NodePath) {
+    this.labels.set(path.node.label.name, path);
+  }
+
   registerDeclaration(path: NodePath) {
     if (path.isLabeledStatement()) {
-      this.registerBinding("label", path);
+      this.registerLabel(path);
     } else if (path.isFunctionDeclaration()) {
       this.registerBinding("hoisted", path.get("id"), path);
     } else if (path.isVariableDeclaration()) {

packages/babel-traverse/test/scope.js

@@ -38,5 +38,27 @@ describe("scope", function () {
     it("purity", function () {
       assert.ok(getPath("({ x: 1 })").get("body")[0].get("expression").isPure());
     });
+
+    test("label", function () {
+      assert.strictEqual(getPath("foo: { }").scope.getBinding("foo"), undefined);
+      assert.strictEqual(getPath("foo: { }").scope.getLabel("foo").type, "LabeledStatement");
+      assert.strictEqual(getPath("foo: { }").scope.getLabel("toString"), undefined);
+
+      assert.strictEqual(getPath(`
+        foo: { }
+      `).scope.generateUid("foo"), "_foo");
+    });
+
+    test("generateUid collision check with labels", function () {
+      assert.strictEqual(getPath(`
+        _foo: { }
+      `).scope.generateUid("foo"), "_foo2");
+
+      assert.strictEqual(getPath(`
+        _foo: { }
+        _foo1: { }
+        _foo2: { }
+      `).scope.generateUid("foo"), "_foo3");
+    });
   });
 });