Support patterns in default argument assignments by writing to a temp…

…orary variable (closes #29)
rpetrich · May 25, 2019 · ce67368 · ce67368
1 parent 58855e8
commit ce67368
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Showing 6 changed files with 24 additions and 2 deletions.
diff --git a/async-to-promises.ts b/async-to-promises.ts
@@ -1,4 +1,4 @@
-import { ArrowFunctionExpression, AwaitExpression, BlockStatement, CallExpression, ClassMethod, File, LabeledStatement, Node, Expression, FunctionDeclaration, Statement, Identifier, ForStatement, ForInStatement, SpreadElement, ReturnStatement, ForOfStatement, Function, FunctionExpression, MemberExpression, NumericLiteral, ThisExpression, SwitchCase, Program, VariableDeclaration, VariableDeclarator, StringLiteral, BooleanLiteral, Pattern, LVal, YieldExpression } from "babel-types";
+import { ArrowFunctionExpression, AwaitExpression, BlockStatement, CallExpression, ClassMethod, File, LabeledStatement, Node, Expression, FunctionDeclaration, Statement, Identifier, ForStatement, ForInStatement, SpreadElement, ReturnStatement, ForOfStatement, Function, FunctionExpression, MemberExpression, NumericLiteral, ThisExpression, SwitchCase, Program, VariableDeclaration, VariableDeclarator, StringLiteral, BooleanLiteral, Pattern, LVal, ObjectPattern, YieldExpression } from "babel-types";
 import { NodePath, Scope, Visitor } from "babel-traverse";
 import { code as helperCode } from "./helpers-string";
 
@@ -3312,12 +3312,23 @@ export default function({ types, template, traverse, transformFromAst, version }
 			if (param.isAssignmentPattern()) {
 				const init = param.get("right");
 				if (!isExpressionOfLiterals(init, literals)) {
-					const id = param.get("left").node;
+					const left = param.get("left") as NodePath<Identifier | ObjectPattern>;
+					let id: Identifier;
+					let after: Statement | undefined;
+					if (left.isIdentifier()) {
+						id = left.node;
+					} else {
+						id = left.scope.generateUidIdentifier(`arg${i}`);
+						after = types.variableDeclaration("let", [types.variableDeclarator(left.node, id)]);
+					}
 					const initNode = init.node;
 					param.replaceWith(id);
 					const isMissing = types.binaryExpression("===", id, types.identifier("undefined"));
 					const assignment = types.expressionStatement(types.assignmentExpression("=", id, initNode));
 					statements.push(types.ifStatement(isMissing, assignment));
+					if (after) {
+						statements.push(after);
+					}
 				}
 			} else if (param.isIdentifier()) {
 				literals.push(param.node.name);

diff --git a/tests/default argument pattern/hoisted.js b/tests/default argument pattern/hoisted.js
@@ -0,0 +1 @@
+const f=_async(function(_arg){if(_arg===undefined)_arg=(x++,{});let{y=(z++,{})}=_arg;});let x=0,z=0;
diff --git a/tests/default argument pattern/inlined.js b/tests/default argument pattern/inlined.js
diff --git a/tests/default argument pattern/input.js b/tests/default argument pattern/input.js
@@ -0,0 +1,4 @@
+let x = 0, z = 0;
+
+async function f({y = (z++, {})} = (x++, {})) {
+}
diff --git a/tests/default argument pattern/options.json b/tests/default argument pattern/options.json
@@ -0,0 +1,4 @@
+{
+	"checkSyntax": false,
+	"module": true
+}
diff --git a/tests/default argument pattern/output.js b/tests/default argument pattern/output.js
@@ -0,0 +1 @@
+const f=_async((_arg)=>{if(_arg===undefined)_arg=(x++,{});let{y=(z++,{})}=_arg;});let x=0,z=0;