support for binary comma operator (#375)

tomblind · web-flow · commit 535f93fe3baa · 2019-01-30T05:43:45.000-07:00
diff --git a/src/LuaTransformer.ts b/src/LuaTransformer.ts
@@ -1037,6 +1037,11 @@ export class LuaTransformer {
             } else if (expression.operatorToken.kind === ts.SyntaxKind.EqualsToken) {
                 // = assignment
                 return this.transformAssignmentStatement(expression);
+
+            } else if (expression.operatorToken.kind === ts.SyntaxKind.CommaToken) {
+                const lhs = this.transformExpressionStatement(expression.left);
+                const rhs = this.transformExpressionStatement(expression.right);
+                return tstl.createDoStatement([lhs, rhs], expression);
             }
 
         } else if (
@@ -1701,6 +1706,13 @@ export class LuaTransformer {
             case ts.SyntaxKind.InstanceOfKeyword:
                 return this.transformLuaLibFunction(LuaLibFeature.InstanceOf, lhs, rhs);
 
+            case ts.SyntaxKind.CommaToken:
+                return this.createImmediatelyInvokedFunctionExpression(
+                    [this.transformExpressionStatement(expression.left)],
+                    rhs,
+                    expression
+                );
+
             default:
                 throw TSTLErrors.UnsupportedKind("binary operator", expression.operatorToken.kind, expression);
         }
diff --git a/test/unit/expressions.spec.ts b/test/unit/expressions.spec.ts
@@ -177,6 +177,28 @@ export class ExpressionTests {
         Expect(util.transpileString(input)).toBe(lua);
     }
 
+    @TestCase("bar(),foo()", 1)
+    @TestCase("foo(),bar()", 2)
+    @TestCase("foo(),bar(),baz()", 3)
+    @Test("Binary Comma")
+    public binaryComma(input: string, expectResult: number): void {
+        const code =
+            `function foo() { return 1; }
+            function bar() { return 2; };
+            function baz() { return 3; };
+            return (${input});`;
+        Expect(util.transpileAndExecute(code)).toBe(expectResult);
+    }
+
+    @Test("Binary Comma Statement in For Loop")
+    public binaryCommaStatementInForLoop(): void {
+        const code =
+            `let x: number, y: number;
+            for (x = 0, y = 17; x < 5; ++x, --y) {}
+            return y;`;
+        Expect(util.transpileAndExecute(code)).toBe(12);
+    }
+
     @Test("Null Expression")
     public nullExpression(): void {
         Expect(util.transpileString("null")).toBe("nil;");
