From e354754b2a30ab9ff558a029fb869a30668dd0ae Mon Sep 17 00:00:00 2001
From: Andrew Casey <andrew.casey@microsoft.com>
Date: Wed, 10 Jan 2018 18:28:47 -0800
Subject: [PATCH] Special case arrow functions with only parameter unused

Fixes GH #18274
---
 src/services/codefixes/fixUnusedIdentifier.ts | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/services/codefixes/fixUnusedIdentifier.ts b/src/services/codefixes/fixUnusedIdentifier.ts
index b7d948b3deb..bcfcd6d1e6d 100644
--- a/src/services/codefixes/fixUnusedIdentifier.ts
+++ b/src/services/codefixes/fixUnusedIdentifier.ts
@@ -121,9 +121,20 @@ namespace ts.codefix {
                 break;
 
             case SyntaxKind.Parameter:
-                const functionDeclaration = <FunctionDeclaration>parent.parent;
-                if (functionDeclaration.parameters.length === 1) {
-                    changes.deleteNode(sourceFile, parent);
+                const oldFunction = parent.parent;
+                if (isArrowFunction(oldFunction) && oldFunction.parameters.length === 1) {
+                    const newFunction = updateArrowFunction(
+                        oldFunction,
+                        oldFunction.modifiers,
+                        oldFunction.typeParameters,
+                        /*parameters*/ undefined,
+                        oldFunction.type,
+                        oldFunction.equalsGreaterThanToken,
+                        oldFunction.body);
+
+                    suppressLeadingAndTrailingTrivia(newFunction);
+
+                    changes.replaceRange(sourceFile, { pos: oldFunction.getStart(), end: oldFunction.end }, newFunction);
                 }
                 else {
                     changes.deleteNodeInList(sourceFile, parent);