Cherry-pick PR #44290 into release-4.3 (#44425)

Component commits:
f3bf29a fix(44273): preserves 'override' modifier in JavaScript output

Co-authored-by: Oleksandr T <[email protected]>

Author: TypeScript Bot

src/compiler/transformers/ts.ts

@@ -368,6 +368,7 @@ namespace ts {
                 case SyntaxKind.PrivateKeyword:
                 case SyntaxKind.ProtectedKeyword:
                 case SyntaxKind.AbstractKeyword:
+                case SyntaxKind.OverrideKeyword:
                 case SyntaxKind.ConstKeyword:
                 case SyntaxKind.DeclareKeyword:
                 case SyntaxKind.ReadonlyKeyword:

tests/baselines/reference/override16(target=es2015).js

@@ -0,0 +1,19 @@
+//// [override16.ts]
+class A {
+    foo?: string;
+}
+
+class B extends A {
+    override foo = "string";
+}
+
+
+//// [override16.js]
+class A {
+}
+class B extends A {
+    constructor() {
+        super(...arguments);
+        this.foo = "string";
+    }
+}

tests/baselines/reference/override16(target=es2015).symbols

@@ -0,0 +1,16 @@
+=== tests/cases/conformance/override/override16.ts ===
+class A {
+>A : Symbol(A, Decl(override16.ts, 0, 0))
+
+    foo?: string;
+>foo : Symbol(A.foo, Decl(override16.ts, 0, 9))
+}
+
+class B extends A {
+>B : Symbol(B, Decl(override16.ts, 2, 1))
+>A : Symbol(A, Decl(override16.ts, 0, 0))
+
+    override foo = "string";
+>foo : Symbol(B.foo, Decl(override16.ts, 4, 19))
+}
+

tests/baselines/reference/override16(target=es2015).types

@@ -0,0 +1,17 @@
+=== tests/cases/conformance/override/override16.ts ===
+class A {
+>A : A
+
+    foo?: string;
+>foo : string
+}
+
+class B extends A {
+>B : B
+>A : A
+
+    override foo = "string";
+>foo : string
+>"string" : "string"
+}
+

tests/baselines/reference/override16(target=esnext).js

@@ -0,0 +1,17 @@
+//// [override16.ts]
+class A {
+    foo?: string;
+}
+
+class B extends A {
+    override foo = "string";
+}
+
+
+//// [override16.js]
+class A {
+    foo;
+}
+class B extends A {
+    foo = "string";
+}

tests/baselines/reference/override16(target=esnext).symbols

@@ -0,0 +1,16 @@
+=== tests/cases/conformance/override/override16.ts ===
+class A {
+>A : Symbol(A, Decl(override16.ts, 0, 0))
+
+    foo?: string;
+>foo : Symbol(A.foo, Decl(override16.ts, 0, 9))
+}
+
+class B extends A {
+>B : Symbol(B, Decl(override16.ts, 2, 1))
+>A : Symbol(A, Decl(override16.ts, 0, 0))
+
+    override foo = "string";
+>foo : Symbol(B.foo, Decl(override16.ts, 4, 19))
+}
+

tests/baselines/reference/override16(target=esnext).types

@@ -0,0 +1,17 @@
+=== tests/cases/conformance/override/override16.ts ===
+class A {
+>A : A
+
+    foo?: string;
+>foo : string
+}
+
+class B extends A {
+>B : B
+>A : A
+
+    override foo = "string";
+>foo : string
+>"string" : "string"
+}
+

tests/baselines/reference/override16.js

@@ -0,0 +1,17 @@
+//// [override16.ts]
+class A {
+    foo?: string;
+}
+
+class B extends A {
+    override foo = "string";
+}
+
+
+//// [override16.js]
+class A {
+    foo;
+}
+class B extends A {
+    foo = "string";
+}

tests/baselines/reference/override16.symbols

@@ -0,0 +1,16 @@
+=== tests/cases/conformance/override/override16.ts ===
+class A {
+>A : Symbol(A, Decl(override16.ts, 0, 0))
+
+    foo?: string;
+>foo : Symbol(A.foo, Decl(override16.ts, 0, 9))
+}
+
+class B extends A {
+>B : Symbol(B, Decl(override16.ts, 2, 1))
+>A : Symbol(A, Decl(override16.ts, 0, 0))
+
+    override foo = "string";
+>foo : Symbol(B.foo, Decl(override16.ts, 4, 19))
+}
+

tests/baselines/reference/override16.types

@@ -0,0 +1,17 @@
+=== tests/cases/conformance/override/override16.ts ===
+class A {
+>A : A
+
+    foo?: string;
+>foo : string
+}
+
+class B extends A {
+>B : B
+>A : A
+
+    override foo = "string";
+>foo : string
+>"string" : "string"
+}
+