From 75f948af0c34c58846be0ac58ec980b2fd454a45 Mon Sep 17 00:00:00 2001
From: Nayeem Rahman <nayeemrmn99@gmail.com>
Date: Sat, 10 Apr 2021 21:41:15 +0100
Subject: [PATCH] Reland #9774

---
 cli/ast.rs                                       | 1 +
 cli/lsp/language_server.rs                       | 1 +
 cli/module_graph.rs                              | 2 ++
 cli/tests/091_use_define_for_class_fields.ts     | 4 ++++
 cli/tests/091_use_define_for_class_fields.ts.out | 4 ++++
 cli/tests/integration_tests.rs                   | 6 ++++++
 cli/tsc_config.rs                                | 1 +
 7 files changed, 19 insertions(+)
 create mode 100644 cli/tests/091_use_define_for_class_fields.ts
 create mode 100644 cli/tests/091_use_define_for_class_fields.ts.out

diff --git a/cli/ast.rs b/cli/ast.rs
index 83d0e16e9bc111..5d2047280386eb 100644
--- a/cli/ast.rs
+++ b/cli/ast.rs
@@ -267,6 +267,7 @@ fn strip_config_from_emit_options(
         typescript::strip::ImportsNotUsedAsValues::Remove
       }
     },
+    use_define_for_class_fields: true,
     ..Default::default()
   }
 }
diff --git a/cli/lsp/language_server.rs b/cli/lsp/language_server.rs
index d1f6c67ecb0810..70682c41ba02b1 100644
--- a/cli/lsp/language_server.rs
+++ b/cli/lsp/language_server.rs
@@ -372,6 +372,7 @@ impl Inner {
       "noEmit": true,
       "strict": true,
       "target": "esnext",
+      "useDefineForClassFields": true,
     }));
     let (maybe_config, maybe_root_uri) = {
       let config = &self.config;
diff --git a/cli/module_graph.rs b/cli/module_graph.rs
index 18cb3209cdf4e5..51e2573396061c 100644
--- a/cli/module_graph.rs
+++ b/cli/module_graph.rs
@@ -803,6 +803,7 @@ impl Graph {
       "strict": true,
       "target": "esnext",
       "tsBuildInfoFile": "deno:///.tsbuildinfo",
+      "useDefineForClassFields": true,
     }));
     if options.emit {
       config.merge(&json!({
@@ -948,6 +949,7 @@ impl Graph {
       "module": "esnext",
       "strict": true,
       "target": "esnext",
+      "useDefineForClassFields": true,
     }));
     let opts = match options.bundle_type {
       BundleType::Esm | BundleType::Iife => json!({
diff --git a/cli/tests/091_use_define_for_class_fields.ts b/cli/tests/091_use_define_for_class_fields.ts
new file mode 100644
index 00000000000000..9be984abf4011d
--- /dev/null
+++ b/cli/tests/091_use_define_for_class_fields.ts
@@ -0,0 +1,4 @@
+class A {
+  b = this.a;
+  constructor(public a: unknown) {}
+}
diff --git a/cli/tests/091_use_define_for_class_fields.ts.out b/cli/tests/091_use_define_for_class_fields.ts.out
new file mode 100644
index 00000000000000..08f94a9671f239
--- /dev/null
+++ b/cli/tests/091_use_define_for_class_fields.ts.out
@@ -0,0 +1,4 @@
+[WILDCARD]error: TS2729 [ERROR]: Property 'a' is used before its initialization.
+  b = this.a;
+           ^
+[WILDCARD]
diff --git a/cli/tests/integration_tests.rs b/cli/tests/integration_tests.rs
index 827fc871b1d7ef..5067b81637e8dc 100644
--- a/cli/tests/integration_tests.rs
+++ b/cli/tests/integration_tests.rs
@@ -2867,6 +2867,12 @@ console.log("finish");
     util::test_pty(args, output, input);
   }
 
+  itest!(_091_use_define_for_class_fields {
+    args: "run 091_use_define_for_class_fields.ts",
+    output: "091_use_define_for_class_fields.ts.out",
+    exit_code: 1,
+  });
+
   itest!(js_import_detect {
     args: "run --quiet --reload js_import_detect.ts",
     output: "js_import_detect.ts.out",
diff --git a/cli/tsc_config.rs b/cli/tsc_config.rs
index 9211f92a5f1d08..0d85adb2ed3ef1 100644
--- a/cli/tsc_config.rs
+++ b/cli/tsc_config.rs
@@ -128,6 +128,7 @@ pub const IGNORED_RUNTIME_COMPILER_OPTIONS: &[&str] = &[
   "traceResolution",
   "tsBuildInfoFile",
   "typeRoots",
+  "useDefineForClassFields",
   "version",
   "watch",
 ];