From 35a9be3b6c703ed059d15abf5cf06583c62669d7 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <nathansa@microsoft.com>
Date: Mon, 15 May 2017 16:22:04 -0700
Subject: [PATCH] Improve arity errors for all calls

Not just ones with a single call signature.
This is pretty great!
---
 src/compiler/checker.ts | 47 +++++++++++++++++++++++------------------
 1 file changed, 26 insertions(+), 21 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 5be1fb633cd..e7e871f12b3 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -15369,28 +15369,33 @@ namespace ts {
                     reportNoCommonSupertypeError(inferenceCandidates, (<JsxOpeningLikeElement>node).tagName || (<CallExpression>node).expression || (<TaggedTemplateExpression>node).tag, diagnosticChainHead);
                 }
             }
+            else if (typeArguments && every(signatures, sig => length(sig.typeParameters) !== typeArguments.length)) {
+                let min = Number.POSITIVE_INFINITY;
+                let max = Number.NEGATIVE_INFINITY;
+                for (const sig of signatures) {
+                    min = Math.min(min, getMinTypeArgumentCount(sig.typeParameters));
+                    max = Math.max(max, length(sig.typeParameters));
+                }
+                const paramMessage = max > min ? `${min}-${max}` : min.toString();
+                reportError(Diagnostics.Expected_0_type_arguments_but_got_1, paramMessage, typeArguments.length.toString());
+            }
+            else if (args) {
+                const argMessage = getSpreadArgumentIndex(args) > -1 ?
+                    "a minimum of " + (args.length - 1) :
+                    args.length.toString();
+                let min = Number.POSITIVE_INFINITY;
+                let max = Number.NEGATIVE_INFINITY;
+                for (const sig of signatures) {
+                    min = Math.min(min, sig.minArgumentCount);
+                    max = Math.max(max, sig.parameters.length);
+                }
+                const paramMessage = some(signatures, sig => sig.hasRestParameter) ? "at least " + min :
+                    min < max ? `${min}-${max}` :
+                    min.toString();
+                reportError(Diagnostics.Expected_0_arguments_but_got_1, paramMessage, argMessage);
+            }
             else {
-                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);
-                }
+                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.