Add tests for JS-inferred rest parameters

tests/cases/compiler/argumentsObjectCreatesRestForJs.ts

@@ -0,0 +1,20 @@
+// @checkJs: true
+// @allowJs: true
+// @Filename: main.js
+// @noemit: true
+function allRest() { arguments; }
+allRest();
+allRest(1, 2, 3);
+function someRest(x, y) { arguments; }
+someRest(); // x and y are still optional because they are in a JS file
+someRest(1, 2, 3);
+
+/**
+ * @param {number} x - a thing
+ */
+function jsdocced(x) { arguments; }
+jsdocced(1);
+
+function dontDoubleRest(x, ...y) { arguments; }
+dontDoubleRest(1, 2, 3);
+

tests/cases/compiler/jsSelfReferencingArgumentsFunction.ts

@@ -0,0 +1,8 @@
+// @Filename: foo.js
+// @noEmit: true
+// @allowJs: true
+// Test #16139
+function Foo() {
+    arguments;
+    return new Foo();
+}

tests/cases/fourslash/signatureHelpCallExpressionJs.ts

@@ -4,14 +4,25 @@
 // @allowJs: true
 
 // @Filename: main.js
-////function fnTest() { arguments; }
-////fnTest(/*1*/);
-////fnTest(1, 2, 3);
+////function allOptional() { arguments; }
+////allOptional(/*1*/);
+////allOptional(1, 2, 3);
+////function someOptional(x, y) { arguments; }
+////someOptional(/*2*/);
+////someOptional(1, 2, 3);
+////someOptional(); // no error here; x and y are optional in JS
 
 goTo.marker('1');
 verify.signatureHelpCountIs(1);
 verify.currentSignatureParameterCountIs(1);
-verify.currentSignatureHelpIs('fnTest(...args: any[]): void');
+verify.currentSignatureHelpIs('allOptional(...args: any[]): void');
 verify.currentParameterHelpArgumentNameIs('args');
 verify.currentParameterSpanIs("...args: any[]");
-verify.numberOfErrorsInCurrentFile(0);
+
+goTo.marker('2');
+verify.signatureHelpCountIs(1);
+verify.currentSignatureParameterCountIs(3);
+verify.currentSignatureHelpIs('someOptional(x: any, y: any, ...args: any[]): void');
+verify.currentParameterHelpArgumentNameIs('x');
+verify.currentParameterSpanIs("x: any");
+verify.numberOfErrorsInCurrentFile(0);