From 93b1eafb9f9d6bd6c82fe99f2ed752d9772285a4 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <nathansa@microsoft.com>
Date: Mon, 15 May 2017 15:25:21 -0700
Subject: [PATCH] Improve arity error messages

For calls with one signature.
---
 src/compiler/checker.ts              | 22 +++++++++++++++++++++-
 src/compiler/diagnosticMessages.json |  8 ++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index d6f56a69b9a..5be1fb633cd 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -15370,7 +15370,27 @@ namespace ts {
                 }
             }
             else {
-                reportError(Diagnostics.Supplied_parameters_do_not_match_any_signature_of_call_target);
+                if (signatures.length === 1) {
+                    if (typeArguments && typeArguments.length !== length(signatures[0].typeParameters)) {
+                        const minTypeArgumentCount = getMinTypeArgumentCount(signatures[0].typeParameters);
+                        const paramMessage = length(signatures[0].typeParameters) > minTypeArgumentCount ?
+                            `${minTypeArgumentCount}-${length(signatures[0].typeParameters)}` :
+                            minTypeArgumentCount.toString();
+                        reportError(Diagnostics.Expected_0_type_arguments_but_got_1, paramMessage, typeArguments.length.toString());
+                    }
+                    else {
+                        const argMessage = getSpreadArgumentIndex(args) > -1 ?
+                            "a minimum of " + (args.length - 1) :
+                            args.length.toString();
+                        const paramMessage = signatures[0].hasRestParameter ? "at least " + signatures[0].minArgumentCount :
+                            signatures[0].minArgumentCount < signatures[0].parameters.length ? `${signatures[0].minArgumentCount}-${signatures[0].parameters.length}` :
+                            signatures[0].minArgumentCount.toString();
+                        reportError(Diagnostics.Expected_0_arguments_but_got_1, paramMessage, argMessage);
+                    }
+                }
+                else {
+                    reportError(Diagnostics.Supplied_parameters_do_not_match_any_signature_of_call_target);
+                }
             }
 
             // No signature was applicable. We have already reported the errors for the invalid signature.
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 4aee7a37a88..849b780380f 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1855,6 +1855,14 @@
         "category": "Error",
         "code": 2552
     },
+    "Expected {0} arguments, but got {1}.": {
+        "category": "Error",
+        "code": 2553
+    },
+    "Expected {0} type arguments, but got {1}.": {
+        "category": "Error",
+        "code": 2554
+    },
     "JSX element attributes type '{0}' may not be a union type.": {
         "category": "Error",
         "code": 2600