Convert unary + or - expressions to numbers (#1635)

Perryvw · web-flow · commit ec84670c5366 · 2025-05-24T16:06:08.000+02:00
diff --git a/src/transformation/visitors/unary-expression.ts b/src/transformation/visitors/unary-expression.ts
@@ -7,6 +7,8 @@ import {
     transformCompoundAssignmentExpression,
     transformCompoundAssignmentStatement,
 } from "./binary-expression/compound";
+import { isNumberType } from "../utils/typescript";
+import { LuaLibFeature, transformLuaLibFunction } from "../utils/lualib";
 
 export function transformUnaryExpressionStatement(
     context: TransformationContext,
@@ -92,16 +94,29 @@ export const transformPrefixUnaryExpression: FunctionVisitor<ts.PrefixUnaryExpre
                 false
             );
 
-        case ts.SyntaxKind.PlusToken:
-            // TODO: Wrap with `Number`
-            return context.transformExpression(expression.operand);
-
-        case ts.SyntaxKind.MinusToken:
-            return lua.createUnaryExpression(
-                context.transformExpression(expression.operand),
-                lua.SyntaxKind.NegationOperator
-            );
-
+        case ts.SyntaxKind.PlusToken: {
+            const operand = context.transformExpression(expression.operand);
+            const type = context.checker.getTypeAtLocation(expression.operand);
+            if (isNumberType(context, type)) {
+                return operand;
+            } else {
+                return transformLuaLibFunction(context, LuaLibFeature.Number, expression, operand);
+            }
+        }
+        case ts.SyntaxKind.MinusToken: {
+            const operand = context.transformExpression(expression.operand);
+            const type = context.checker.getTypeAtLocation(expression.operand);
+            if (isNumberType(context, type)) {
+                return lua.createUnaryExpression(operand, lua.SyntaxKind.NegationOperator);
+            } else {
+                return transformLuaLibFunction(
+                    context,
+                    LuaLibFeature.Number,
+                    expression,
+                    lua.createUnaryExpression(operand, lua.SyntaxKind.NegationOperator)
+                );
+            }
+        }
         case ts.SyntaxKind.ExclamationToken:
             return lua.createUnaryExpression(
                 context.transformExpression(expression.operand),
diff --git a/test/unit/__snapshots__/expressions.spec.ts.snap b/test/unit/__snapshots__/expressions.spec.ts.snap
@@ -589,9 +589,11 @@ return ____exports"
 `;
 
 exports[`Unary expressions basic ("+a") 1`] = `
-"local ____exports = {}
+"local ____lualib = require("lualib_bundle")
+local __TS__Number = ____lualib.__TS__Number
+local ____exports = {}
 function ____exports.__main(self)
-    local ____ = a
+    __TS__Number(a)
 end
 return ____exports"
 `;
@@ -605,9 +607,11 @@ return ____exports"
 `;
 
 exports[`Unary expressions basic ("-a") 1`] = `
-"local ____exports = {}
+"local ____lualib = require("lualib_bundle")
+local __TS__Number = ____lualib.__TS__Number
+local ____exports = {}
 function ____exports.__main(self)
-    local ____ = -a
+    __TS__Number(-a)
 end
 return ____exports"
 `;
diff --git a/test/unit/builtins/numbers.spec.ts b/test/unit/builtins/numbers.spec.ts
@@ -224,3 +224,18 @@ test.each([
 ])("Numer constants have correct relative sizes (%p)", comparison => {
     util.testExpression(comparison).expectToEqual(true);
 });
+
+// https://github.com/TypeScriptToLua/TypeScriptToLua/issues/1629
+test("unary + casting to number (#1629)", () => {
+    util.testFunction`
+        let abc = "123";
+        return [+abc, +"456"];
+    `.expectToEqual([123, 456]);
+});
+
+test("unary - casting to number", () => {
+    util.testFunction`
+        let abc = "123";
+        return [-abc, -"456"];
+    `.expectToEqual([-123, -456]);
+});
