Count the arguments a replaced stdio write receives (#2530)

packages/compiler/src/frontend/lowering/call-signatures.ts

@@ -1062,6 +1062,9 @@ export function lambdaSignature(
         type: DYN,
         mode: "required",
       }));
+      // `arguments` holds the call's own tuple: a console line passes one
+      // or two arguments whatever the replacement declares.
+      appendArgumentsParameter(lowerer, node, shapes, "arguments");
       return { shapes, funcType: funcTypeFromParamShapes(shapes, DYN) };
     }
   }

packages/compiler/test/ts7/baselines/order-parity/tests/corpus/stdio-write-replacement-arguments.cjs.json

@@ -0,0 +1,6 @@
+{
+ "order": [
+  "<repo>/tests/corpus/stdio-write-replacement-arguments.cjs"
+ ],
+ "diags": []
+}

tests/corpus/stdio-write-replacement-arguments.cjs

@@ -0,0 +1,43 @@
+// A replaced process.stdout.write or process.stderr.write sees the call's own
+// arguments: arguments.length is the number the caller passed, whatever the
+// replacement declares.
+const seen = [];
+const originalOut = process.stdout.write;
+process.stdout.write = function (chunk, encodingOrCallback, callback) {
+  seen.push(`stdout declared3 ${arguments.length} ${typeof callback}`);
+  return true;
+};
+process.stdout.write("one");
+process.stdout.write("two", "utf8");
+process.stdout.write("three", "utf8", () => {});
+process.stdout.write = function () {
+  seen.push(`stdout declared0 ${arguments.length} ${arguments[0]}`);
+  return true;
+};
+process.stdout.write("zero");
+process.stdout.write = function (chunk) {
+  seen.push(`stdout declared1 ${arguments.length} ${arguments[1]}`);
+  return true;
+};
+process.stdout.write("a", "latin1");
+process.stdout.write = originalOut;
+const originalErr = process.stderr.write;
+process.stderr.write = function (chunk, encodingOrCallback, callback) {
+  seen.push(`stderr declared3 ${arguments.length} ${typeof callback}`);
+  return true;
+};
+process.stderr.write("one");
+process.stderr.write("two", "utf8");
+process.stderr.write("three", "utf8", () => {});
+process.stderr.write = function () {
+  seen.push(`stderr declared0 ${arguments.length} ${arguments[0]}`);
+  return true;
+};
+process.stderr.write("zero");
+process.stderr.write = function (chunk) {
+  seen.push(`stderr declared1 ${arguments.length} ${arguments[1]}`);
+  return true;
+};
+process.stderr.write("a", "latin1");
+process.stderr.write = originalErr;
+console.log(seen.join("\n"));

tests/harness/corpus-costs/stdio-write-replacement-arguments.cjs.json

@@ -0,0 +1 @@
+{ "plain": 3757, "san": 5000 }