From 856f754fad416da003b76b4116b78e5e51a61943 Mon Sep 17 00:00:00 2001
From: Collins Abitekaniza <abtcolns@gmail.com>
Date: Tue, 14 Aug 2018 15:09:56 +0300
Subject: [PATCH] give suggestions when index signature given

---
 src/compiler/checker.ts              | 27 ++++++++++++++++++++++++++-
 src/compiler/diagnosticMessages.json |  4 ++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 829d11bd09173..af9c5a5f4a0cc 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -9187,7 +9187,13 @@ namespace ts {
                                 }
                             }
                             else {
-                                error(accessExpression, Diagnostics.Element_implicitly_has_an_any_type_because_type_0_has_no_index_signature, typeToString(objectType));
+                                const suggestions = getSuggestionsForNonexistentIndexSignature(objectType);
+                                if (suggestions) {
+                                    error(accessExpression, Diagnostics.Element_implicitly_has_an_any_type_because_type_0_has_no_index_signature_Did_you_mean_to_call_1, typeToString(objectType), suggestions);
+                                }
+                                else {
+                                    error(accessExpression, Diagnostics.Element_implicitly_has_an_any_type_because_type_0_has_no_index_signature, typeToString(objectType));
+                                }
                             }
                         }
                     }
@@ -18159,6 +18165,25 @@ namespace ts {
             return suggestion && symbolName(suggestion);
         }
 
+        function getSuggestionsForNonexistentIndexSignature(objectType: Type): string | undefined {
+            let suggestions: string | undefined;
+            const props = [
+                getPropertyOfObjectType(objectType, <__String>"get"),
+                getPropertyOfObjectType(objectType, <__String>"set")
+            ];
+
+            for (const prop of props) {
+                if (prop) {
+                    const s = getSingleCallSignature(getTypeOfSymbol(prop));
+                    if (s && getMinArgumentCount(s) === 1 && typeToString(getTypeAtPosition(s, 0)) === "string") {
+                        const suggestion = symbolToString(objectType.symbol) + "." + symbolToString(prop);
+                        suggestions = (!suggestions) ? suggestion : suggestions.concat(" or " + suggestion);
+                    }
+                }
+            }
+            return suggestions;
+        }
+
         /**
          * Given a name and a list of symbols whose names are *not* equal to the name, return a spelling suggestion if there is one that is close enough.
          * Names less than length 3 only check for case-insensitive equality, not levenshtein distance.
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 6000c48de4dc3..7379a649a3efe 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -3945,6 +3945,10 @@
         "category": "Error",
         "code": 7042
     },
+    "Element implicitly has an 'any' type because type '{0}' has no index signature. Did you mean to call '{1}' ?": {
+        "category": "Error",
+        "code": 7043
+    },
     "You cannot rename this element.": {
         "category": "Error",
         "code": 8000