Handle out-of-order binding of identifiers to improve tree-shaking (#2803)

Author: lukastaegert

src/ast/nodes/Identifier.ts

@@ -86,6 +86,7 @@ export default class Identifier extends NodeBase implements PatternNode {
 		recursionTracker: ImmutableEntityPathTracker,
 		origin: DeoptimizableEntity
 	): LiteralValueOrUnknown {
+		if (!this.bound) this.bind();
 		if (this.variable !== null) {
 			return this.variable.getLiteralValueAtPath(path, recursionTracker, origin);
 		}
@@ -97,6 +98,7 @@ export default class Identifier extends NodeBase implements PatternNode {
 		recursionTracker: ImmutableEntityPathTracker,
 		origin: DeoptimizableEntity
 	) {
+		if (!this.bound) this.bind();
 		if (this.variable !== null) {
 			return this.variable.getReturnExpressionWhenCalledAtPath(path, recursionTracker, origin);
 		}

test/form/samples/simplify-return-expression/_config.js

@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'Simplifies conditionals in return expression'
+};

test/form/samples/simplify-return-expression/_expected.js

@@ -0,0 +1,14 @@
+const test = () => {
+	console.log(foo());
+	console.log(bar());
+};
+
+const foo = () => {
+	return A;
+};
+
+const bar = () => {
+	return A;
+};
+
+export { test };

test/form/samples/simplify-return-expression/main.js

@@ -0,0 +1,16 @@
+export const test = () => {
+	console.log(foo());
+	console.log(bar());
+};
+
+const foo = () => {
+	return BUILD ? A : B;
+};
+
+const bar = () => {
+	return getBuild() ? A : B;
+};
+
+const getBuild = () => BUILD;
+
+const BUILD = true;