From 31d721d60eac2a70368071d7a6a048da5fe359a6 Mon Sep 17 00:00:00 2001
From: "Pranav Senthilnathan (from Dev Box)" <pranas@microsoft.com>
Date: Fri, 17 Nov 2023 11:36:29 -0800
Subject: [PATCH] add index signature

---
 src/services/inlayHints.ts                    | 12 +++
 ...nteractiveFunctionParameterTypes1.baseline | 79 ++++++++++++++++++-
 ...HintsInteractiveFunctionParameterTypes1.ts |  6 ++
 3 files changed, 93 insertions(+), 4 deletions(-)

diff --git a/src/services/inlayHints.ts b/src/services/inlayHints.ts
index a36e4054911a1..3946d9a135e80 100644
--- a/src/services/inlayHints.ts
+++ b/src/services/inlayHints.ts
@@ -53,6 +53,7 @@ import {
     isIdentifierText,
     isImportTypeNode,
     isIndexedAccessTypeNode,
+    isIndexSignatureDeclaration,
     isInferTypeNode,
     isInfinityOrNaNString,
     isIntersectionTypeNode,
@@ -743,6 +744,17 @@ export function provideInlayHints(context: InlayHintsContext): InlayHint[] {
                         visitForDisplayParts(node.type);
                     }
                     break;
+                case SyntaxKind.IndexSignature:
+                    Debug.assertNode(node, isIndexSignatureDeclaration);
+                    Debug.assertEqual(node.parameters.length, 1);
+                    parts.push({ text: "[" });
+                    visitForDisplayParts(node.parameters[0]);
+                    parts.push({ text: "]" });
+                    if (node.type) {
+                        parts.push({ text: ": " });
+                        visitForDisplayParts(node.type);
+                    }
+                    break;
                 case SyntaxKind.MethodSignature:
                     Debug.assertNode(node, isMethodSignature);
                     if (node.modifiers?.length) {
diff --git a/tests/baselines/reference/inlayHintsInteractiveFunctionParameterTypes1.baseline b/tests/baselines/reference/inlayHintsInteractiveFunctionParameterTypes1.baseline
index 4a36146628873..e845d97ca77e7 100644
--- a/tests/baselines/reference/inlayHintsInteractiveFunctionParameterTypes1.baseline
+++ b/tests/baselines/reference/inlayHintsInteractiveFunctionParameterTypes1.baseline
@@ -262,6 +262,30 @@
     {
       "text": "; "
     },
+    {
+      "text": "["
+    },
+    {
+      "text": "i"
+    },
+    {
+      "text": ": "
+    },
+    {
+      "text": "string"
+    },
+    {
+      "text": "]"
+    },
+    {
+      "text": ": "
+    },
+    {
+      "text": "number"
+    },
+    {
+      "text": "; "
+    },
     {
       "text": "a"
     },
@@ -464,7 +488,7 @@
       "text": "}"
     }
   ],
-  "position": 646,
+  "position": 671,
   "kind": "Type",
   "whitespaceBefore": true
 }
@@ -490,7 +514,7 @@
       "text": "42"
     }
   ],
-  "position": 716,
+  "position": 741,
   "kind": "Type",
   "whitespaceBefore": true
 }
@@ -506,13 +530,60 @@ foo4(p => {})
     {
       "text": "Thing",
       "span": {
-        "start": 735,
+        "start": 760,
         "length": 5
       },
       "file": "/tests/cases/fourslash/inlayHintsInteractiveFunctionParameterTypes1.ts"
     }
   ],
-  "position": 801,
+  "position": 826,
+  "kind": "Type",
+  "whitespaceBefore": true
+}
+
+ const foo5: F4 = (a) => { }
+                    ^
+{
+  "text": "",
+  "displayParts": [
+    {
+      "text": ": "
+    },
+    {
+      "text": "{"
+    },
+    {
+      "text": " "
+    },
+    {
+      "text": "["
+    },
+    {
+      "text": "x"
+    },
+    {
+      "text": ": "
+    },
+    {
+      "text": "string"
+    },
+    {
+      "text": "]"
+    },
+    {
+      "text": ": "
+    },
+    {
+      "text": "number"
+    },
+    {
+      "text": " "
+    },
+    {
+      "text": "}"
+    }
+  ],
+  "position": 910,
   "kind": "Type",
   "whitespaceBefore": true
 }
\ No newline at end of file
diff --git a/tests/cases/fourslash/inlayHintsInteractiveFunctionParameterTypes1.ts b/tests/cases/fourslash/inlayHintsInteractiveFunctionParameterTypes1.ts
index d9c668507aee8..ffca754c9361a 100644
--- a/tests/cases/fourslash/inlayHintsInteractiveFunctionParameterTypes1.ts
+++ b/tests/cases/fourslash/inlayHintsInteractiveFunctionParameterTypes1.ts
@@ -28,6 +28,7 @@
 ////     g<T>(): T
 ////     h?<X, Y>(x: X): Y
 ////     <X, Y>(x: X): Y
+////     [i: string]: number
 //// }) => void
 //// const foo5: F2 = (a) => { }
 
@@ -41,6 +42,11 @@
 ////function foo4(callback: (thing: Thing) => void) {}
 ////foo4(p => {})
 
+//// type F4 = (a: {
+////     [i in string]: number
+//// }) => void
+//// const foo5: F4 = (a) => { }
+
 verify.baselineInlayHints(undefined, {
     includeInlayFunctionParameterTypeHints: true,
     interactiveInlayHints: true,