fix(44377): omit type alias declarations from JavaScript (#44378)

Author: a-tarasyuk

src/compiler/transformers/ts.ts

@@ -411,11 +411,11 @@ namespace ts {
 
                 case SyntaxKind.Decorator:
                     // TypeScript decorators are elided. They will be emitted as part of visitClassDeclaration.
-                    // falls through
+                    return undefined;
 
                 case SyntaxKind.TypeAliasDeclaration:
                     // TypeScript type-only declarations are elided.
-                    return undefined;
+                    return factory.createNotEmittedStatement(node);
 
                 case SyntaxKind.PropertyDeclaration:
                     // TypeScript property declarations are elided. However their names are still visited, and can potentially be retained if they could have sideeffects

tests/baselines/reference/labeledStatementWithLabel.js

@@ -78,4 +78,4 @@ label: var b = 1;
 label: var c = 1;
 label: ;
 label: ;
-label: 
+label: ;

tests/baselines/reference/labeledStatementWithLabel_es2015.js

@@ -42,4 +42,4 @@ label: let b = 1;
 label: const c = 1;
 label: ;
 label: ;
-label: 
+label: ;

tests/baselines/reference/labeledStatementWithLabel_strict.js

@@ -44,4 +44,4 @@ label: let b = 1;
 label: const c = 1;
 label: ;
 label: ;
-label: 
+label: ;

tests/baselines/reference/typeAliasDeclarationEmit3.js

@@ -0,0 +1,36 @@
+//// [typeAliasDeclarationEmit3.ts]
+function f1(): void {
+    for (let i = 0; i < 1; i++)
+        type foo = [];
+        console.log('f1');
+}
+
+function f2(): void {
+    while (true)
+        type foo = [];
+        console.log('f2');
+}
+
+function f3(): void {
+    if (true)
+        type foo = [];
+        console.log('f3');
+}
+
+
+//// [typeAliasDeclarationEmit3.js]
+function f1() {
+    for (var i = 0; i < 1; i++)
+        ;
+    console.log('f1');
+}
+function f2() {
+    while (true)
+        ;
+    console.log('f2');
+}
+function f3() {
+    if (true)
+        ;
+    console.log('f3');
+}

tests/baselines/reference/typeAliasDeclarationEmit3.symbols

@@ -0,0 +1,44 @@
+=== tests/cases/compiler/typeAliasDeclarationEmit3.ts ===
+function f1(): void {
+>f1 : Symbol(f1, Decl(typeAliasDeclarationEmit3.ts, 0, 0))
+
+    for (let i = 0; i < 1; i++)
+>i : Symbol(i, Decl(typeAliasDeclarationEmit3.ts, 1, 12))
+>i : Symbol(i, Decl(typeAliasDeclarationEmit3.ts, 1, 12))
+>i : Symbol(i, Decl(typeAliasDeclarationEmit3.ts, 1, 12))
+
+        type foo = [];
+>foo : Symbol(foo, Decl(typeAliasDeclarationEmit3.ts, 1, 31))
+
+        console.log('f1');
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+}
+
+function f2(): void {
+>f2 : Symbol(f2, Decl(typeAliasDeclarationEmit3.ts, 4, 1))
+
+    while (true)
+        type foo = [];
+>foo : Symbol(foo, Decl(typeAliasDeclarationEmit3.ts, 7, 16))
+
+        console.log('f2');
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+}
+
+function f3(): void {
+>f3 : Symbol(f3, Decl(typeAliasDeclarationEmit3.ts, 10, 1))
+
+    if (true)
+        type foo = [];
+>foo : Symbol(foo, Decl(typeAliasDeclarationEmit3.ts, 13, 13))
+
+        console.log('f3');
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+}
+

tests/baselines/reference/typeAliasDeclarationEmit3.types

@@ -0,0 +1,58 @@
+=== tests/cases/compiler/typeAliasDeclarationEmit3.ts ===
+function f1(): void {
+>f1 : () => void
+
+    for (let i = 0; i < 1; i++)
+>i : number
+>0 : 0
+>i < 1 : boolean
+>i : number
+>1 : 1
+>i++ : number
+>i : number
+
+        type foo = [];
+>foo : []
+
+        console.log('f1');
+>console.log('f1') : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>'f1' : "f1"
+}
+
+function f2(): void {
+>f2 : () => void
+
+    while (true)
+>true : true
+
+        type foo = [];
+>foo : []
+
+        console.log('f2');
+>console.log('f2') : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>'f2' : "f2"
+}
+
+function f3(): void {
+>f3 : () => void
+
+    if (true)
+>true : true
+
+        type foo = [];
+>foo : []
+
+        console.log('f3');
+>console.log('f3') : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>'f3' : "f3"
+}
+

tests/cases/compiler/typeAliasDeclarationEmit3.ts

@@ -0,0 +1,17 @@
+function f1(): void {
+    for (let i = 0; i < 1; i++)
+        type foo = [];
+        console.log('f1');
+}
+
+function f2(): void {
+    while (true)
+        type foo = [];
+        console.log('f2');
+}
+
+function f3(): void {
+    if (true)
+        type foo = [];
+        console.log('f3');
+}