From d7b35ac85eb30c08b141570da0292b140ade1e07 Mon Sep 17 00:00:00 2001
From: Perryvw <perryvw@users.noreply.github.com>
Date: Tue, 26 Nov 2024 21:10:02 +0100
Subject: [PATCH] Transform String(x) to tostring(x)

---
 src/transformation/builtins/global.ts |  3 +++
 src/transformation/builtins/index.ts  |  4 ++--
 src/transformation/builtins/string.ts | 10 +++++++++-
 test/unit/builtins/string.spec.ts     | 15 +++++++++++++++
 4 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/src/transformation/builtins/global.ts b/src/transformation/builtins/global.ts
index 4d882b293..288414a60 100644
--- a/src/transformation/builtins/global.ts
+++ b/src/transformation/builtins/global.ts
@@ -4,6 +4,7 @@ import { TransformationContext } from "../context";
 import { LuaLibFeature, transformLuaLibFunction } from "../utils/lualib";
 import { isNumberType } from "../utils/typescript";
 import { transformArguments } from "../visitors/call";
+import { transformStringConstructorCall } from "./string";
 
 export function tryTransformBuiltinGlobalCall(
     context: TransformationContext,
@@ -21,6 +22,8 @@ export function tryTransformBuiltinGlobalCall(
             return transformLuaLibFunction(context, LuaLibFeature.Symbol, node, ...getParameters());
         case "NumberConstructor":
             return transformLuaLibFunction(context, LuaLibFeature.Number, node, ...getParameters());
+        case "StringConstructor":
+            return transformStringConstructorCall(node, ...getParameters());
         case "isNaN":
         case "isFinite":
             const numberParameters = isNumberType(context, expressionType)
diff --git a/src/transformation/builtins/index.ts b/src/transformation/builtins/index.ts
index 867942064..85a4c9802 100644
--- a/src/transformation/builtins/index.ts
+++ b/src/transformation/builtins/index.ts
@@ -14,7 +14,7 @@ import { transformMathCall, transformMathProperty } from "./math";
 import { transformNumberConstructorCall, transformNumberPrototypeCall, transformNumberProperty } from "./number";
 import { transformObjectConstructorCall, tryTransformObjectPrototypeCall } from "./object";
 import { transformPromiseConstructorCall } from "./promise";
-import { transformStringConstructorCall, transformStringProperty, transformStringPrototypeCall } from "./string";
+import { transformStringConstructorMethodCall, transformStringProperty, transformStringPrototypeCall } from "./string";
 import { transformSymbolConstructorCall } from "./symbol";
 import { unsupportedBuiltinOptionalCall } from "../utils/diagnostics";
 import { LuaTarget } from "../../CompilerOptions";
@@ -101,7 +101,7 @@ function tryTransformBuiltinGlobalMethodCall(
             result = transformMathCall(context, node, calledMethod);
             break;
         case "StringConstructor":
-            result = transformStringConstructorCall(context, node, calledMethod);
+            result = transformStringConstructorMethodCall(context, node, calledMethod);
             break;
         case "ObjectConstructor":
             result = transformObjectConstructorCall(context, node, calledMethod);
diff --git a/src/transformation/builtins/string.ts b/src/transformation/builtins/string.ts
index b7c56a08c..98bd62303 100644
--- a/src/transformation/builtins/string.ts
+++ b/src/transformation/builtins/string.ts
@@ -160,7 +160,7 @@ export function transformStringPrototypeCall(
     }
 }
 
-export function transformStringConstructorCall(
+export function transformStringConstructorMethodCall(
     context: TransformationContext,
     node: ts.CallExpression,
     calledMethod: ts.PropertyAccessExpression
@@ -202,3 +202,11 @@ export function transformStringProperty(
             context.diagnostics.push(unsupportedProperty(node.name, "string", node.name.text));
     }
 }
+
+export function transformStringConstructorCall(
+    originalNode: ts.CallExpression,
+    ...args: lua.Expression[]
+): lua.Expression | undefined {
+    const tostring = lua.createIdentifier("tostring", originalNode.expression);
+    return lua.createCallExpression(tostring, args, originalNode);
+}
diff --git a/test/unit/builtins/string.spec.ts b/test/unit/builtins/string.spec.ts
index fecb0e466..977944e55 100644
--- a/test/unit/builtins/string.spec.ts
+++ b/test/unit/builtins/string.spec.ts
@@ -372,6 +372,21 @@ test("string intersected method", () => {
     `.expectToMatchJsResult();
 });
 
+test("tostring number with String constructor", () => {
+    util.testFunction`
+        const n = 123
+        return "abc:" + String(n);
+    `.expectToEqual("abc:123");
+});
+
+test("tostring table with String constructor", () => {
+    const result = util.testFunction`
+        const t = {}
+        return "abc:" + String(t);
+    `.getLuaExecutionResult();
+    expect(result).toContain("abc:table: 0x");
+});
+
 // Issue #1218: https://github.com/TypeScriptToLua/TypeScriptToLua/issues/1218
 test.each(['"foo"', "undefined"])("prototype call on nullable string (%p)", value => {
     util.testFunction`