From 46b53d7308e0ad5d4ba431fb9c2cc52fe1a532d3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hu=C3=A1ng=20J=C3=B9nli=C3=A0ng?= <jlhwung@gmail.com>
Date: Sat, 7 Nov 2020 10:51:42 -0500
Subject: [PATCH] simplify toAssignable

---
 .../babel-parser/src/parser/expression.js     |  6 ------
 packages/babel-parser/src/parser/lval.js      | 20 +++++++++----------
 packages/babel-parser/src/plugins/estree.js   |  8 ++------
 .../src/plugins/typescript/index.js           | 10 +++++-----
 4 files changed, 17 insertions(+), 27 deletions(-)

diff --git a/packages/babel-parser/src/parser/expression.js b/packages/babel-parser/src/parser/expression.js
index 59221e8ca91e..56ef4188f7e4 100644
--- a/packages/babel-parser/src/parser/expression.js
+++ b/packages/babel-parser/src/parser/expression.js
@@ -1409,12 +1409,6 @@ export default class ExpressionParser extends LValParser {
     ) {
       this.expressionScope.validateAsPattern();
       this.expressionScope.exit();
-      for (const param of exprList) {
-        if (param.extra && param.extra.parenthesized) {
-          this.unexpected(param.extra.parenStart);
-        }
-      }
-
       this.parseArrowExpression(arrowNode, exprList, false);
       return arrowNode;
     }
diff --git a/packages/babel-parser/src/parser/lval.js b/packages/babel-parser/src/parser/lval.js
index 7aaac489018d..1a8b7d7b6d08 100644
--- a/packages/babel-parser/src/parser/lval.js
+++ b/packages/babel-parser/src/parser/lval.js
@@ -98,7 +98,7 @@ export default class LValParser extends NodeUtils {
         ) {
           const prop = node.properties[i];
           const isLast = i === last;
-          this.toAssignableObjectExpressionProp(prop, isLast, isLHS);
+          this.toAssignableObjectExpressionProp(prop, isLast);
 
           if (
             isLast &&
@@ -111,7 +111,8 @@ export default class LValParser extends NodeUtils {
         break;
 
       case "ObjectProperty":
-        this.toAssignable(node.value, isLHS);
+        // ObjectProperty is not allowed in LHS
+        this.toAssignable(node.value, /* isLHS */ false);
         break;
 
       case "SpreadElement": {
@@ -135,7 +136,8 @@ export default class LValParser extends NodeUtils {
 
         node.type = "AssignmentPattern";
         delete node.operator;
-        this.toAssignable(node.left, isLHS);
+        // AssignmentPattern is not allowed in LHS
+        this.toAssignable(node.left, /* isLHS */ false);
         break;
 
       case "ParenthesizedExpression":
@@ -149,11 +151,7 @@ export default class LValParser extends NodeUtils {
     return node;
   }
 
-  toAssignableObjectExpressionProp(
-    prop: Node,
-    isLast: boolean,
-    isLHS: boolean,
-  ) {
+  toAssignableObjectExpressionProp(prop: Node, isLast: boolean) {
     if (prop.type === "ObjectMethod") {
       const error =
         prop.kind === "get" || prop.kind === "set"
@@ -166,7 +164,8 @@ export default class LValParser extends NodeUtils {
     } else if (prop.type === "SpreadElement" && !isLast) {
       this.raiseRestNotLast(prop.start);
     } else {
-      this.toAssignable(prop, isLHS);
+      // ObjectPattern is not allowed in LHS
+      this.toAssignable(prop, /* isLHS */ false);
     }
   }
 
@@ -184,8 +183,9 @@ export default class LValParser extends NodeUtils {
         --end;
       } else if (last?.type === "SpreadElement") {
         last.type = "RestElement";
-        const arg = last.argument;
+        let arg = last.argument;
         this.toAssignable(arg, isLHS);
+        arg = unwrapParenthesizedExpression(arg);
         if (
           arg.type !== "Identifier" &&
           arg.type !== "MemberExpression" &&
diff --git a/packages/babel-parser/src/plugins/estree.js b/packages/babel-parser/src/plugins/estree.js
index 7c313e77f12d..8111cd2891e3 100644
--- a/packages/babel-parser/src/plugins/estree.js
+++ b/packages/babel-parser/src/plugins/estree.js
@@ -351,17 +351,13 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       return super.toAssignable(node, isLHS);
     }
 
-    toAssignableObjectExpressionProp(
-      prop: N.Node,
-      isLast: boolean,
-      isLHS: boolean,
-    ) {
+    toAssignableObjectExpressionProp(prop: N.Node, isLast: boolean) {
       if (prop.kind === "get" || prop.kind === "set") {
         throw this.raise(prop.key.start, Errors.PatternHasAccessor);
       } else if (prop.method) {
         throw this.raise(prop.key.start, Errors.PatternHasMethod);
       } else {
-        super.toAssignableObjectExpressionProp(prop, isLast, isLHS);
+        super.toAssignableObjectExpressionProp(prop, isLast);
       }
     }
 
diff --git a/packages/babel-parser/src/plugins/typescript/index.js b/packages/babel-parser/src/plugins/typescript/index.js
index 6c0de5314747..ba6544e72ca2 100644
--- a/packages/babel-parser/src/plugins/typescript/index.js
+++ b/packages/babel-parser/src/plugins/typescript/index.js
@@ -2596,19 +2596,19 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       return param;
     }
 
-    toAssignable(node: N.Node): N.Node {
+    toAssignable(node: N.Node, isLHS: boolean = false): N.Node {
       switch (node.type) {
         case "TSTypeCastExpression":
-          return super.toAssignable(this.typeCastToParameter(node));
+          return super.toAssignable(this.typeCastToParameter(node), isLHS);
         case "TSParameterProperty":
-          return super.toAssignable(node);
+          return super.toAssignable(node, isLHS);
         case "TSAsExpression":
         case "TSNonNullExpression":
         case "TSTypeAssertion":
-          node.expression = this.toAssignable(node.expression);
+          node.expression = this.toAssignable(node.expression, isLHS);
           return node;
         default:
-          return super.toAssignable(node);
+          return super.toAssignable(node, isLHS);
       }
     }