add diagnostic message for call signature length mismatch

Author: bakkot

src/compiler/checker.ts

@@ -18480,6 +18480,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         const sourceHasMoreParameters = !hasEffectiveRestParameter(target) &&
             (checkMode & SignatureCheckMode.StrictArity ? hasEffectiveRestParameter(source) || getParameterCount(source) > targetCount : getMinArgumentCount(source) > targetCount);
         if (sourceHasMoreParameters) {
+            if (reportErrors) {
+                errorReporter!(Diagnostics.Call_signature_0_expects_more_arguments_than_call_signature_1, signatureToString(source), signatureToString(target));
+            }
             return Ternary.False;
         }
 

src/compiler/diagnosticMessages.json

@@ -3563,6 +3563,10 @@
         "category": "Error",
         "code": 2845
     },
+    "Call signature '{0}' expects more arguments than call signature '{1}'.": {
+        "category": "Error",
+        "code": 2846
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

tests/baselines/reference/signatureLengthMismatchCall.errors.txt

@@ -0,0 +1,14 @@
+tests/cases/compiler/signatureLengthMismatchCall.ts(5,15): error TS2345: Argument of type '(a: number, b: number) => void' is not assignable to parameter of type '(a: number) => void'.
+  Call signature '(a: number, b: number): void' expects more arguments than call signature '(a: number): void'.
+
+
+==== tests/cases/compiler/signatureLengthMismatchCall.ts (1 errors) ====
+    function takesCallback(fn: (a: number) => void) {
+      // ...
+    }
+    
+    takesCallback((a: number, b: number) => {});
+                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2345: Argument of type '(a: number, b: number) => void' is not assignable to parameter of type '(a: number) => void'.
+!!! error TS2345:   Call signature '(a: number, b: number): void' expects more arguments than call signature '(a: number): void'.
+    

tests/baselines/reference/signatureLengthMismatchCall.js

@@ -0,0 +1,13 @@
+//// [signatureLengthMismatchCall.ts]
+function takesCallback(fn: (a: number) => void) {
+  // ...
+}
+
+takesCallback((a: number, b: number) => {});
+
+
+//// [signatureLengthMismatchCall.js]
+function takesCallback(fn) {
+    // ...
+}
+takesCallback(function (a, b) { });

tests/baselines/reference/signatureLengthMismatchCall.symbols

@@ -0,0 +1,14 @@
+=== tests/cases/compiler/signatureLengthMismatchCall.ts ===
+function takesCallback(fn: (a: number) => void) {
+>takesCallback : Symbol(takesCallback, Decl(signatureLengthMismatchCall.ts, 0, 0))
+>fn : Symbol(fn, Decl(signatureLengthMismatchCall.ts, 0, 23))
+>a : Symbol(a, Decl(signatureLengthMismatchCall.ts, 0, 28))
+
+  // ...
+}
+
+takesCallback((a: number, b: number) => {});
+>takesCallback : Symbol(takesCallback, Decl(signatureLengthMismatchCall.ts, 0, 0))
+>a : Symbol(a, Decl(signatureLengthMismatchCall.ts, 4, 15))
+>b : Symbol(b, Decl(signatureLengthMismatchCall.ts, 4, 25))
+

tests/baselines/reference/signatureLengthMismatchCall.types

@@ -0,0 +1,16 @@
+=== tests/cases/compiler/signatureLengthMismatchCall.ts ===
+function takesCallback(fn: (a: number) => void) {
+>takesCallback : (fn: (a: number) => void) => void
+>fn : (a: number) => void
+>a : number
+
+  // ...
+}
+
+takesCallback((a: number, b: number) => {});
+>takesCallback((a: number, b: number) => {}) : void
+>takesCallback : (fn: (a: number) => void) => void
+>(a: number, b: number) => {} : (a: number, b: number) => void
+>a : number
+>b : number
+

tests/cases/compiler/signatureLengthMismatchCall.ts

@@ -0,0 +1,5 @@
+function takesCallback(fn: (a: number) => void) {
+  // ...
+}
+
+takesCallback((a: number, b: number) => {});