From ef79b42b57bdd2ef4924331f701d5376f79405e8 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Tue, 21 Feb 2023 18:05:02 -0800
Subject: [PATCH] Don't emit binding pattern pattern / optional parameter error
 when an initializer is present (#52880)

---
 src/compiler/checker.ts                             |  2 +-
 .../reference/optionalBindingParameters4.symbols    | 12 ++++++++++++
 .../reference/optionalBindingParameters4.types      | 13 +++++++++++++
 .../es6/destructuring/optionalBindingParameters4.ts | 11 +++++++++++
 4 files changed, 37 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/optionalBindingParameters4.symbols
 create mode 100644 tests/baselines/reference/optionalBindingParameters4.types
 create mode 100644 tests/cases/conformance/es6/destructuring/optionalBindingParameters4.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 06632f9394f..c0b9802d402 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -37648,7 +37648,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 error(node.name, Diagnostics.constructor_cannot_be_used_as_a_parameter_property_name);
             }
         }
-        if ((node.questionToken || isJSDocOptionalParameter(node)) && isBindingPattern(node.name) && (func as FunctionLikeDeclaration).body) {
+        if (!node.initializer && isOptionalDeclaration(node) && isBindingPattern(node.name) && (func as FunctionLikeDeclaration).body) {
             error(node, Diagnostics.A_binding_pattern_parameter_cannot_be_optional_in_an_implementation_signature);
         }
         if (node.name && isIdentifier(node.name) && (node.name.escapedText === "this" || node.name.escapedText === "new")) {
diff --git a/tests/baselines/reference/optionalBindingParameters4.symbols b/tests/baselines/reference/optionalBindingParameters4.symbols
new file mode 100644
index 00000000000..4ff4cd66c76
--- /dev/null
+++ b/tests/baselines/reference/optionalBindingParameters4.symbols
@@ -0,0 +1,12 @@
+=== /a.js ===
+/** 
+* @param {{ cause?: string }} [options] 
+*/ 
+function foo({ cause } = {}) {
+>foo : Symbol(foo, Decl(a.js, 0, 0))
+>cause : Symbol(cause, Decl(a.js, 3, 14))
+
+    return cause;
+>cause : Symbol(cause, Decl(a.js, 3, 14))
+}
+
diff --git a/tests/baselines/reference/optionalBindingParameters4.types b/tests/baselines/reference/optionalBindingParameters4.types
new file mode 100644
index 00000000000..ddc4c1e8a72
--- /dev/null
+++ b/tests/baselines/reference/optionalBindingParameters4.types
@@ -0,0 +1,13 @@
+=== /a.js ===
+/** 
+* @param {{ cause?: string }} [options] 
+*/ 
+function foo({ cause } = {}) {
+>foo : ({ cause }?: {    cause?: string;}) => string
+>cause : string
+>{} : {}
+
+    return cause;
+>cause : string
+}
+
diff --git a/tests/cases/conformance/es6/destructuring/optionalBindingParameters4.ts b/tests/cases/conformance/es6/destructuring/optionalBindingParameters4.ts
new file mode 100644
index 00000000000..40a468ad287
--- /dev/null
+++ b/tests/cases/conformance/es6/destructuring/optionalBindingParameters4.ts
@@ -0,0 +1,11 @@
+// @checkJs: true
+// @allowJs: true
+// @noEmit: true
+// @filename: /a.js
+
+/** 
+* @param {{ cause?: string }} [options] 
+*/ 
+function foo({ cause } = {}) {
+    return cause;
+}