Forward deopt node path in NodePath#evaludate (#11832)

* Forward deopt node path

* Move deopt evaluation tests

* Document evaluate deopt property

packages/babel-traverse/src/path/evaluation.js

@@ -219,7 +219,7 @@ function _evaluate(path, state) {
       if (elemValue.confident) {
         arr.push(elemValue.value);
       } else {
-        return deopt(elem, state);
+        return deopt(elemValue.deopt, state);
       }
     }
     return arr;
@@ -237,7 +237,7 @@ function _evaluate(path, state) {
       if (prop.node.computed) {
         key = key.evaluate();
         if (!key.confident) {
-          return deopt(keyPath, state);
+          return deopt(key.deopt, state);
         }
         key = key.value;
       } else if (key.isIdentifier()) {
@@ -248,7 +248,7 @@ function _evaluate(path, state) {
       const valuePath = prop.get("value");
       let value = valuePath.evaluate();
       if (!value.confident) {
-        return deopt(valuePath, state);
+        return deopt(value.deopt, state);
       }
       value = value.value;
       obj[key] = value;
@@ -407,19 +407,24 @@ function evaluateQuasis(path, quasis: Array<Object>, state, raw = false) {
 /**
  * Walk the input `node` and statically evaluate it.
  *
- * Returns an object in the form `{ confident, value }`. `confident` indicates
+ * Returns an object in the form `{ confident, value, deopt }`. `confident`
- * whether or not we had to drop out of evaluating the expression because of
+ * indicates whether or not we had to drop out of evaluating the expression
- * hitting an unknown node that we couldn't confidently find the value of.
+ * because of hitting an unknown node that we couldn't confidently find the
+ * value of, in which case `deopt` is the path of said node.
  *
  * Example:
  *
  *   t.evaluate(parse("5 + 5")) // { confident: true, value: 10 }
  *   t.evaluate(parse("!true")) // { confident: true, value: false }
- *   t.evaluate(parse("foo + foo")) // { confident: false, value: undefined }
+ *   t.evaluate(parse("foo + foo")) // { confident: false, value: undefined, deopt: NodePath }
  *
  */
 
-export function evaluate(): { confident: boolean, value: any } {
+export function evaluate(): {
+  confident: boolean,
+  value: any,
+  deopt?: NodePath,
+} {
   const state = {
     confident: true,
     deoptPath: null,

packages/babel-traverse/test/evaluation.js

@@ -13,6 +13,25 @@ function getPath(code) {
   return path;
 }
 
+function addDeoptTest(code, type, expectedType) {
+  it(type + " deopt: " + code, function () {
+    const visitor = {};
+
+    visitor[type] = function (path) {
+      const evaluate = path.evaluate();
+      expect(evaluate.confident).toBeFalsy();
+      expect(evaluate.deopt.type).toEqual(expectedType);
+    };
+
+    traverse(
+      parse(code, {
+        plugins: ["*"],
+      }),
+      visitor,
+    );
+  });
+}
+
 describe("evaluation", function () {
   describe("evaluateTruthy", function () {
     it("it should work with null", function () {
@@ -228,4 +247,8 @@ describe("evaluation", function () {
     expect(result.deopt).toBeNull();
     expect(result.value).toEqual(["foo", "bar"]);
   });
+
+  addDeoptTest("({a:{b}})", "ObjectExpression", "Identifier");
+  addDeoptTest("({[a + 'b']: 1})", "ObjectExpression", "Identifier");
+  addDeoptTest("[{a}]", "ArrayExpression", "Identifier");
 });