From 74f03130c17c9261a0edbd452adc56589d1ace3c Mon Sep 17 00:00:00 2001
From: Timothee Guerin <tiguerin@microsoft.com>
Date: Mon, 10 Apr 2023 09:26:39 -0700
Subject: [PATCH 1/3] Fix: Missing index wrong location

---
 packages/compiler/core/checker.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/compiler/core/checker.ts b/packages/compiler/core/checker.ts
index c5ce4176cf0..78ada106810 100644
--- a/packages/compiler/core/checker.ts
+++ b/packages/compiler/core/checker.ts
@@ -4819,7 +4819,7 @@ export function createChecker(program: Program): Checker {
                 indexType: getTypeName(target.indexer.key),
                 sourceType: getTypeName(source),
               },
-              target,
+              target: diagnosticTarget,
             }),
           ],
         ];

From 99b61714a6eeaf13e92fae09009e34d903cb5ede Mon Sep 17 00:00:00 2001
From: Timothee Guerin <tiguerin@microsoft.com>
Date: Mon, 10 Apr 2023 09:27:25 -0700
Subject: [PATCH 2/3] changelog

---
 ...x-missing-index-diag-location_2023-04-10-16-27.json | 10 ++++++++++
 1 file changed, 10 insertions(+)
 create mode 100644 common/changes/@typespec/compiler/fix-missing-index-diag-location_2023-04-10-16-27.json

diff --git a/common/changes/@typespec/compiler/fix-missing-index-diag-location_2023-04-10-16-27.json b/common/changes/@typespec/compiler/fix-missing-index-diag-location_2023-04-10-16-27.json
new file mode 100644
index 00000000000..ace13fce21e
--- /dev/null
+++ b/common/changes/@typespec/compiler/fix-missing-index-diag-location_2023-04-10-16-27.json
@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@typespec/compiler",
+      "comment": "Fix: `missing-index` diagnostic showing at the wrong location",
+      "type": "none"
+    }
+  ],
+  "packageName": "@typespec/compiler"
+}
\ No newline at end of file

From db8ba7343bf769d29b172b300392e8eff9cd2218 Mon Sep 17 00:00:00 2001
From: Timothee Guerin <tiguerin@microsoft.com>
Date: Mon, 10 Apr 2023 09:37:44 -0700
Subject: [PATCH 3/3] Add tests for location

---
 .../compiler/test/checker/relation.test.ts    | 35 ++++++++++++-------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/packages/compiler/test/checker/relation.test.ts b/packages/compiler/test/checker/relation.test.ts
index fce35d881b9..478a0427d49 100644
--- a/packages/compiler/test/checker/relation.test.ts
+++ b/packages/compiler/test/checker/relation.test.ts
@@ -1,5 +1,5 @@
 import { deepStrictEqual, ok, strictEqual } from "assert";
-import { Model } from "../../core/index.js";
+import { Diagnostic, Model, ModelPropertyNode } from "../../core/index.js";
 import {
   BasicTestRunner,
   createTestHost,
@@ -7,6 +7,7 @@ import {
   DiagnosticMatch,
   expectDiagnosticEmpty,
   expectDiagnostics,
+  extractCursor,
 } from "../../testing/index.js";
 
 interface RelatedTypeOptions {
@@ -21,32 +22,40 @@ describe("compiler: checker: type relations", () => {
     runner = createTestWrapper(await createTestHost());
   });
 
-  async function checkTypeAssignable({ source, target, commonCode }: RelatedTypeOptions) {
-    const { Test } = (await runner.compile(`
+  async function checkTypeAssignable({ source, target, commonCode }: RelatedTypeOptions): Promise<{
+    related: boolean;
+    diagnostics: readonly Diagnostic[];
+    expectedDiagnosticPos: number;
+  }> {
+    const { source: code, pos } = extractCursor(`
     ${commonCode ?? ""}
     
     @test model Test {
-      source: ${source};
+      source: ┆${source};
       target: ${target};
-    }`)) as { Test: Model };
+    }`);
+    const { Test } = (await runner.compile(code)) as { Test: Model };
     const sourceProp = Test.properties.get("source")!.type;
     const targetProp = Test.properties.get("target")!.type;
-    return runner.program.checker.isTypeAssignableTo(sourceProp, targetProp, targetProp);
+
+    const [related, diagnostics] = runner.program.checker.isTypeAssignableTo(
+      sourceProp,
+      targetProp,
+      (Test.properties.get("source")!.node! as ModelPropertyNode).value
+    );
+    return { related, diagnostics, expectedDiagnosticPos: pos };
   }
 
   async function expectTypeAssignable(options: RelatedTypeOptions) {
-    const [related, diagnostics] = await checkTypeAssignable(options);
+    const { related, diagnostics } = await checkTypeAssignable(options);
     expectDiagnosticEmpty(diagnostics);
     ok(related, `Type ${options.source} should be assignable to ${options.target}`);
   }
 
-  async function expectTypeNotAssignable(
-    options: RelatedTypeOptions,
-    match: DiagnosticMatch | DiagnosticMatch[]
-  ) {
-    const [related, diagnostics] = await checkTypeAssignable(options);
+  async function expectTypeNotAssignable(options: RelatedTypeOptions, match: DiagnosticMatch) {
+    const { related, diagnostics, expectedDiagnosticPos } = await checkTypeAssignable(options);
     ok(!related, `Type ${options.source} should NOT be assignable to ${options.target}`);
-    expectDiagnostics(diagnostics, match);
+    expectDiagnostics(diagnostics, { ...match, pos: expectedDiagnosticPos });
   }
 
   describe("model with indexer", () => {