Fix not emitted statement in then clauses producing syntactically invalid output

src/compiler/factory.ts

@@ -1544,8 +1544,8 @@ namespace ts {
     export function createIf(expression: Expression, thenStatement: Statement, elseStatement?: Statement) {
         const node = <IfStatement>createSynthesizedNode(SyntaxKind.IfStatement);
         node.expression = expression;
-        node.thenStatement = thenStatement;
-        node.elseStatement = elseStatement;
+        node.thenStatement = asEmbeddedStatement(thenStatement);
+        node.elseStatement = asEmbeddedStatement(elseStatement);
         return node;
     }
 
@@ -1559,7 +1559,7 @@ namespace ts {
 
     export function createDo(statement: Statement, expression: Expression) {
         const node = <DoStatement>createSynthesizedNode(SyntaxKind.DoStatement);
-        node.statement = statement;
+        node.statement = asEmbeddedStatement(statement);
         node.expression = expression;
         return node;
     }
@@ -1574,7 +1574,7 @@ namespace ts {
     export function createWhile(expression: Expression, statement: Statement) {
         const node = <WhileStatement>createSynthesizedNode(SyntaxKind.WhileStatement);
         node.expression = expression;
-        node.statement = statement;
+        node.statement = asEmbeddedStatement(statement);
         return node;
     }
 
@@ -1590,7 +1590,7 @@ namespace ts {
         node.initializer = initializer;
         node.condition = condition;
         node.incrementor = incrementor;
-        node.statement = statement;
+        node.statement = asEmbeddedStatement(statement);
         return node;
     }
 
@@ -1607,7 +1607,7 @@ namespace ts {
         const node = <ForInStatement>createSynthesizedNode(SyntaxKind.ForInStatement);
         node.initializer = initializer;
         node.expression = expression;
-        node.statement = statement;
+        node.statement = asEmbeddedStatement(statement);
         return node;
     }
 
@@ -1624,7 +1624,7 @@ namespace ts {
         node.awaitModifier = awaitModifier;
         node.initializer = initializer;
         node.expression = expression;
-        node.statement = statement;
+        node.statement = asEmbeddedStatement(statement);
         return node;
     }
 
@@ -1676,7 +1676,7 @@ namespace ts {
     export function createWith(expression: Expression, statement: Statement) {
         const node = <WithStatement>createSynthesizedNode(SyntaxKind.WithStatement);
         node.expression = expression;
-        node.statement = statement;
+        node.statement = asEmbeddedStatement(statement);
         return node;
     }
 
@@ -1704,7 +1704,7 @@ namespace ts {
     export function createLabel(label: string | Identifier, statement: Statement) {
         const node = <LabeledStatement>createSynthesizedNode(SyntaxKind.LabeledStatement);
         node.label = asName(label);
-        node.statement = statement;
+        node.statement = asEmbeddedStatement(statement);
         return node;
     }
 
@@ -3080,6 +3080,12 @@ namespace ts {
         return typeof value === "number" ? createToken(value) : value;
     }
 
+    function asEmbeddedStatement<T extends Node>(statement: T): T | EmptyStatement;
+    function asEmbeddedStatement<T extends Node>(statement: T | undefined): T | EmptyStatement | undefined;
+    function asEmbeddedStatement<T extends Node>(statement: T | undefined): T | EmptyStatement | undefined {
+        return statement && isNotEmittedStatement(statement) ? setTextRange(setOriginalNode(createEmptyStatement(), statement), statement) : statement;
+    }
+
     /**
      * Clears any EmitNode entries from parse-tree nodes.
      * @param sourceFile A source file.

tests/baselines/reference/constEnum4.js

@@ -9,5 +9,8 @@ else
 
 //// [constEnum4.js]
 if (1)
+    ;
 else if (2)
+    ;
 else
+    ;

tests/baselines/reference/elidedEmbeddedStatementsReplacedWithSemicolon.js

@@ -0,0 +1,47 @@
+//// [elidedEmbeddedStatementsReplacedWithSemicolon.ts]
+if (1)
+    const enum A {}
+else
+    const enum B {}
+
+do
+    const enum C {}
+while (0);
+
+while (0)
+    const enum D {}
+
+for (;0;)
+    const enum E {}
+
+for (let _ in [])
+    const enum F {}
+
+for (let _ of [])
+    const enum G {}
+
+// @ts-ignore suppress `with` statement error
+with (window)
+    const enum H {}
+
+//// [elidedEmbeddedStatementsReplacedWithSemicolon.js]
+if (1)
+    ;
+else
+    ;
+do
+    ;
+while (0);
+while (0)
+    ;
+for (; 0;)
+    ;
+for (var _ in [])
+    ;
+for (var _i = 0, _a = []; _i < _a.length; _i++) {
+    var _ = _a[_i];
+    ;
+}
+// @ts-ignore suppress `with` statement error
+with (window)
+    ;

tests/baselines/reference/elidedEmbeddedStatementsReplacedWithSemicolon.symbols

@@ -0,0 +1,40 @@
+=== tests/cases/compiler/elidedEmbeddedStatementsReplacedWithSemicolon.ts ===
+if (1)
+    const enum A {}
+>A : Symbol(A, Decl(elidedEmbeddedStatementsReplacedWithSemicolon.ts, 0, 6))
+
+else
+    const enum B {}
+>B : Symbol(B, Decl(elidedEmbeddedStatementsReplacedWithSemicolon.ts, 2, 4))
+
+do
+    const enum C {}
+>C : Symbol(C, Decl(elidedEmbeddedStatementsReplacedWithSemicolon.ts, 5, 2))
+
+while (0);
+
+while (0)
+    const enum D {}
+>D : Symbol(D, Decl(elidedEmbeddedStatementsReplacedWithSemicolon.ts, 9, 9))
+
+for (;0;)
+    const enum E {}
+>E : Symbol(E, Decl(elidedEmbeddedStatementsReplacedWithSemicolon.ts, 12, 9))
+
+for (let _ in [])
+>_ : Symbol(_, Decl(elidedEmbeddedStatementsReplacedWithSemicolon.ts, 15, 8))
+
+    const enum F {}
+>F : Symbol(F, Decl(elidedEmbeddedStatementsReplacedWithSemicolon.ts, 15, 17))
+
+for (let _ of [])
+>_ : Symbol(_, Decl(elidedEmbeddedStatementsReplacedWithSemicolon.ts, 18, 8))
+
+    const enum G {}
+>G : Symbol(G, Decl(elidedEmbeddedStatementsReplacedWithSemicolon.ts, 18, 17))
+
+// @ts-ignore suppress `with` statement error
+with (window)
+>window : Symbol(window, Decl(lib.dom.d.ts, --, --))
+
+    const enum H {}

tests/baselines/reference/elidedEmbeddedStatementsReplacedWithSemicolon.types

@@ -0,0 +1,51 @@
+=== tests/cases/compiler/elidedEmbeddedStatementsReplacedWithSemicolon.ts ===
+if (1)
+>1 : 1
+
+    const enum A {}
+>A : A
+
+else
+    const enum B {}
+>B : B
+
+do
+    const enum C {}
+>C : C
+
+while (0);
+>0 : 0
+
+while (0)
+>0 : 0
+
+    const enum D {}
+>D : D
+
+for (;0;)
+>0 : 0
+
+    const enum E {}
+>E : E
+
+for (let _ in [])
+>_ : string
+>[] : undefined[]
+
+    const enum F {}
+>F : F
+
+for (let _ of [])
+>_ : any
+>[] : undefined[]
+
+    const enum G {}
+>G : G
+
+// @ts-ignore suppress `with` statement error
+with (window)
+>window : Window
+
+    const enum H {}
+>H : error
+

tests/baselines/reference/labeledStatementWithLabel.js

@@ -64,7 +64,7 @@ label: {
     (function (E) {
     })(E || (E = {}));
 }
-label: 
+label: ;
 label: {
     var C = /** @class */ (function () {
         function C() {
@@ -75,6 +75,6 @@ label: {
 label: var a = 1;
 label: var b = 1;
 label: var c = 1;
-label: 
-label: 
+label: ;
+label: ;
 label: 

tests/baselines/reference/labeledStatementWithLabel_es2015.js

@@ -33,12 +33,12 @@ label: {
     (function (E) {
     })(E || (E = {}));
 }
-label: 
+label: ;
 label: class C {
 }
 label: var a = 1;
 label: let b = 1;
 label: const c = 1;
-label: 
-label: 
+label: ;
+label: ;
 label: 

tests/baselines/reference/labeledStatementWithLabel_strict.js

@@ -35,12 +35,12 @@ label: {
     (function (E) {
     })(E || (E = {}));
 }
-label: 
+label: ;
 label: class C {
 }
 label: var a = 1;
 label: let b = 1;
 label: const c = 1;
-label: 
-label: 
+label: ;
+label: ;
 label: 

tests/cases/compiler/elidedEmbeddedStatementsReplacedWithSemicolon.ts

@@ -0,0 +1,24 @@
+if (1)
+    const enum A {}
+else
+    const enum B {}
+
+do
+    const enum C {}
+while (0);
+
+while (0)
+    const enum D {}
+
+for (;0;)
+    const enum E {}
+
+for (let _ in [])
+    const enum F {}
+
+for (let _ of [])
+    const enum G {}
+
+// @ts-ignore suppress `with` statement error
+with (window)
+    const enum H {}