Hoisting fixes (#2607)

When hoisting a var, use UNKNOWN_EXPRESSION as the initializer instead
of the actual one. This prevents the initializer from being used during
the optimization step when it hasn't yet been assigned at runtime.

src/ast/scopes/BlockScope.ts

@@ -1,6 +1,7 @@
 import { AstContext } from '../../Module';
 import Identifier from '../nodes/Identifier';
 import { ExpressionEntity } from '../nodes/shared/Expression';
+import { UNKNOWN_EXPRESSION } from '../values';
 import LocalVariable from '../variables/LocalVariable';
 import Scope from './Scope';
 
@@ -14,7 +15,12 @@ export default class BlockScope extends Scope {
 		isHoisted: boolean = false
 	) {
 		if (isHoisted) {
-			return this.parent.addDeclaration(identifier, context, init, true) as LocalVariable;
+			return this.parent.addDeclaration(
+				identifier,
+				context,
+				UNKNOWN_EXPRESSION,
+				true
+			) as LocalVariable;
 		} else {
 			return super.addDeclaration(identifier, context, init, false) as LocalVariable;
 		}

test/form/samples/hoisted-variable-case-stmt/_config.js

@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'Properly handles a variable hoisted from within a fallthrough switch case'
+};

test/form/samples/hoisted-variable-case-stmt/_expected.js

@@ -0,0 +1,8 @@
+switch (someGlobal) {
+    case 1:
+        var hoisted = true;
+    case 2:
+        if (hoisted) {
+            throw "failed";
+        }
+}

test/form/samples/hoisted-variable-case-stmt/main.js

@@ -0,0 +1,8 @@
+switch (someGlobal) {
+    case 1:
+        var hoisted = true;
+    case 2:
+        if (hoisted) {
+            throw "failed";
+        }
+}

test/form/samples/hoisted-variable-if-stmt/_config.js

@@ -0,0 +1,4 @@
+module.exports = {
+	description:
+		'Properly renders branches which refer to hoisted variables from other lexical scopes'
+};

test/form/samples/hoisted-variable-if-stmt/_expected.js

@@ -0,0 +1,15 @@
+if (false) {
+    var foo;
+}
+
+if (foo) {
+    console.log("nope");
+}
+
+{
+    var bar = true;
+}
+
+if (bar) {
+    console.log("ok");
+}

test/form/samples/hoisted-variable-if-stmt/main.js

@@ -0,0 +1,15 @@
+if (false) {
+    var foo = true;
+}
+
+if (foo) {
+    console.log("nope");
+}
+
+if (true) {
+    var bar = true;
+}
+
+if (bar) {
+    console.log("ok");
+}