Destructuring nothing fix (#453)

tomblind · web-flow · commit 777d62c649d5 · 2019-02-26T05:55:24.000-07:00
* fixes for empty destructuring

* cleanup

* union destructuring test

* removing duplicate test
diff --git a/src/LuaTransformer.ts b/src/LuaTransformer.ts
@@ -1673,7 +1673,9 @@ export class LuaTransformer {
                 throw TSTLErrors.ForbiddenEllipsisDestruction(statement);
             }
 
-            const vars = statement.name.elements.map(e => this.transformArrayBindingElement(e));
+            const vars = statement.name.elements.length > 0
+                ? statement.name.elements.map(e => this.transformArrayBindingElement(e))
+                : tstl.createAnnonymousIdentifier(statement.name);
 
             // Don't unpack TupleReturn decorated functions
             if (statement.initializer) {
@@ -2448,10 +2450,14 @@ export class LuaTransformer {
 
         if (ts.isArrayLiteralExpression(expression.left)) {
             // Destructuring assignment
-            const left = expression.left.elements.map(e => this.transformExpression(e));
+            const left = expression.left.elements.length > 0
+                ? expression.left.elements.map(e => this.transformExpression(e))
+                : [tstl.createAnnonymousIdentifier(expression.left)];
             let right: tstl.Expression[];
             if (ts.isArrayLiteralExpression(expression.right)) {
-                right = expression.right.elements.map(e => this.transformExpression(e));
+                right = expression.right.elements.length > 0
+                    ? expression.right.elements.map(e => this.transformExpression(e))
+                    : [tstl.createNilLiteral()];
             } else if (tsHelper.isTupleReturnCall(expression.right, this.checker)) {
                 right = [this.transformExpression(expression.right)];
             } else {
@@ -2479,16 +2485,20 @@ export class LuaTransformer {
         if (ts.isArrayLiteralExpression(expression.left)) {
             // Destructuring assignment
             // (function() local ${tmps} = ${right}; ${left} = ${tmps}; return {${tmps}} end)()
-            const left = expression.left.elements.map(e => this.transformExpression(e));
+            const left = expression.left.elements.length > 0
+                ? expression.left.elements.map(e => this.transformExpression(e))
+                : [tstl.createAnnonymousIdentifier(expression.left)];
             let right: tstl.Expression[];
             if (ts.isArrayLiteralExpression(expression.right)) {
-                right = expression.right.elements.map(e => this.transformExpression(e));
+                right = expression.right.elements.length > 0
+                    ? expression.right.elements.map(e => this.transformExpression(e))
+                    : [tstl.createNilLiteral()];
             } else if (tsHelper.isTupleReturnCall(expression.right, this.checker)) {
                 right = [this.transformExpression(expression.right)];
             } else {
                 right = [this.createUnpackCall(this.transformExpression(expression.right), expression.right)];
             }
-            const tmps = expression.left.elements.map((_, i) => tstl.createIdentifier(`____TS_tmp${i}`));
+            const tmps = left.map((_, i) => tstl.createIdentifier(`____TS_tmp${i}`));
             const statements: tstl.Statement[] = [
                 tstl.createVariableDeclarationStatement(tmps, right),
                 tstl.createAssignmentStatement(left as tstl.IdentifierOrTableIndexExpression[], tmps),
@@ -4191,6 +4201,9 @@ export class LuaTransformer {
 
         const fromTypeNode = this.checker.typeToTypeNode(fromType);
         const toTypeNode = this.checker.typeToTypeNode(toType);
+        if (!fromTypeNode || !toTypeNode) {
+            return;
+        }
 
         if ((ts.isArrayTypeNode(toTypeNode) || ts.isTupleTypeNode(toTypeNode))
             && (ts.isArrayTypeNode(fromTypeNode) || ts.isTupleTypeNode(fromTypeNode))) {
diff --git a/test/unit/assignmentDestructuring.spec.ts b/test/unit/assignmentDestructuring.spec.ts
@@ -37,4 +37,27 @@ export class AssignmentDestructuringTests {
         // Assert
         Expect(lua).toBe(`local a, b = unpack(myFunc());`);
     }
+
+    @TestCase("function foo(): [] { return []; }; let [] = foo();")
+    @TestCase("let [] = ['a', 'b', 'c'];")
+    @TestCase("let [] = [];")
+    @TestCase("let [] = [] = [];")
+    @TestCase("function foo(): [] { return []; }; [] = foo();")
+    @TestCase("[] = ['a', 'b', 'c'];")
+    @TestCase("[] = [];")
+    @TestCase("[] = [] = [];")
+    @Test("Empty destructuring")
+    public emptyDestructuring(code: string): void {
+        Expect(() => util.transpileAndExecute(code)).not.toThrow();
+    }
+
+    @Test("Union destructuring")
+    public unionDestructuring(): void {
+        const code =
+            `function foo(): [string] | [] { return ["bar"]; }
+            let x: string;
+            [x] = foo();
+            return x;`;
+        Expect(util.transpileAndExecute(code)).toBe("bar");
+    }
 }
