From 4f15024d3066c36e4c02ddc0bad91c24d5faf1ba Mon Sep 17 00:00:00 2001
From: Congcong Cai <congcongcai0907@163.com>
Date: Wed, 15 Nov 2023 08:45:52 +0800
Subject: [PATCH] fix: add diagnose when initializing field in interface
 (#2797)

---
 src/diagnosticMessages.json                    | 1 +
 src/program.ts                                 | 4 ++++
 tests/compiler/interface-with-initializer.json | 7 +++++++
 tests/compiler/interface-with-initializer.ts   | 9 +++++++++
 4 files changed, 21 insertions(+)
 create mode 100644 tests/compiler/interface-with-initializer.json
 create mode 100644 tests/compiler/interface-with-initializer.ts

diff --git a/src/diagnosticMessages.json b/src/diagnosticMessages.json
index e15946207a..3ff9e9f162 100644
--- a/src/diagnosticMessages.json
+++ b/src/diagnosticMessages.json
@@ -119,6 +119,7 @@
   "Decorators are not valid here.": 1206,
   "'abstract' modifier can only appear on a class, method, or property declaration.": 1242,
   "Method '{0}' cannot have an implementation because it is marked abstract.": 1245,
+  "An interface property cannot have an initializer.": 1246,
   "A definite assignment assertion '!' is not permitted in this context.": 1255,
   "A class may only extend another class.": 1311,
   "A parameter property cannot be declared using a rest parameter.": 1317,
diff --git a/src/program.ts b/src/program.ts
index 1f9849eec2..3174be4875 100644
--- a/src/program.ts
+++ b/src/program.ts
@@ -2671,6 +2671,10 @@ export class Program extends DiagnosticEmitter {
     /** Parent interface. */
     parent: InterfacePrototype
   ): void {
+    let initializer = declaration.initializer;
+    if (initializer) {
+      this.error(DiagnosticCode.An_interface_property_cannot_have_an_initializer, initializer.range);
+    }
     let typeNode = declaration.type;
     if (!typeNode) typeNode = Node.createOmittedType(declaration.name.range.atEnd);
     this.initializeProperty(
diff --git a/tests/compiler/interface-with-initializer.json b/tests/compiler/interface-with-initializer.json
new file mode 100644
index 0000000000..be54c01a3f
--- /dev/null
+++ b/tests/compiler/interface-with-initializer.json
@@ -0,0 +1,7 @@
+{
+  "asc_flags": [
+  ],
+  "stderr": [
+    "TS1246: An interface property cannot have an initializer."
+  ]
+}
diff --git a/tests/compiler/interface-with-initializer.ts b/tests/compiler/interface-with-initializer.ts
new file mode 100644
index 0000000000..c1d5689042
--- /dev/null
+++ b/tests/compiler/interface-with-initializer.ts
@@ -0,0 +1,9 @@
+interface I {
+  v: string = "";
+}
+
+class C implements I {
+  v: string = "";
+}
+
+new C();