Report diagnostics for unused "using" and "import" so that they will be shown properly in ide

.chronus/changes/unused-import-namespace-2024-10-18-21-32-11.md

@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@typespec/compiler"
+---
+
+Support diagnostics for unused import and using statements

.chronus/changes/unused-import-namespace-2024-10-23-11-18-0.md

@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: fix
+packages:
+  - "@typespec/http-specs"
+---
+
+Remove unnecessary "import" and "using" from tsp code

.chronus/changes/unused-import-namespace-2024-10-23-19-12-55.md

@@ -0,0 +1,7 @@
+---
+changeKind: internal
+packages:
+  - "@typespec/rest"
+---
+
+Update test code to handle diagnostics for unnecessary code

packages/compiler/src/core/compiler-code-fixes/remove-unnecessary-code.codefix.ts

@@ -0,0 +1,16 @@
+import { defineCodeFix, getSourceLocation } from "../diagnostics.js";
+import { type ImportStatementNode, type UsingStatementNode } from "../types.js";
+
+/**
+ * Quick fix that remove unnecessary code.
+ */
+export function removeUnnecessaryCodeCodeFix(node: ImportStatementNode | UsingStatementNode) {
+  return defineCodeFix({
+    id: "remove-unnecessary-code",
+    label: `Remove unnecessary code`,
+    fix: (context) => {
+      const location = getSourceLocation(node);
+      return context.replaceText(location, "");
+    },
+  });
+}

packages/compiler/src/core/diagnostics.ts

@@ -33,7 +33,7 @@ export type DiagnosticHandler = (diagnostic: Diagnostic) => void;
 export function logDiagnostics(diagnostics: readonly Diagnostic[], logger: LogSink) {
   for (const diagnostic of diagnostics) {
     logger.log({
-      level: diagnostic.severity,
+      level: diagnostic.severity === "hint" ? "trace" : diagnostic.severity,
       message: diagnostic.message,
       code: diagnostic.code,
       url: diagnostic.url,
@@ -52,7 +52,7 @@ export function formatDiagnostic(diagnostic: Diagnostic, options: FormatDiagnost
   return formatLog(
     {
       code: diagnostic.code,
-      level: diagnostic.severity,
+      level: diagnostic.severity === "hint" ? "trace" : diagnostic.severity,
       message: diagnostic.message,
       url: diagnostic.url,
       sourceLocation: getSourceLocation(diagnostic.target, { locateId: true }),

packages/compiler/src/core/messages.ts

@@ -576,6 +576,12 @@ const diagnostics = {
       default: "The #deprecated directive cannot be used more than once on the same declaration.",
     },
   },
+  unnecessary: {
+    severity: "hint",
+    messages: {
+      default: paramMessage`Unnecessary code: ${"code"}`,
+    },
+  },
 
   /**
    * Configuration