From 246b66c714aa6ac93e6e168a933cc1f18807c10c Mon Sep 17 00:00:00 2001
From: uhyo <uhyo@uhy.ooo>
Date: Thu, 2 May 2019 01:16:25 +0900
Subject: [PATCH] add related info to error for use of for-await-of in
 non-async function

---
 src/compiler/checker.ts | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 2ae614b2dd8f1..728c10dcf5637 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -31598,7 +31598,20 @@ namespace ts {
 
             if (forInOrOfStatement.kind === SyntaxKind.ForOfStatement && forInOrOfStatement.awaitModifier) {
                 if ((forInOrOfStatement.flags & NodeFlags.AwaitContext) === NodeFlags.None) {
-                    return grammarErrorOnNode(forInOrOfStatement.awaitModifier, Diagnostics.A_for_await_of_statement_is_only_allowed_within_an_async_function_or_async_generator);
+                    // use of 'for-await-of' in non-async function
+                    const sourceFile = getSourceFileOfNode(forInOrOfStatement);
+                    if (!hasParseDiagnostics(sourceFile)) {
+                        const diagnostic = createDiagnosticForNode(forInOrOfStatement.awaitModifier, Diagnostics.A_for_await_of_statement_is_only_allowed_within_an_async_function_or_async_generator);
+                        const func = getContainingFunction(forInOrOfStatement);
+                        if (func) {
+                            Debug.assert((getFunctionFlags(func) & FunctionFlags.Async) === 0, "Enclosing function should never be an async function.");
+                            const relatedInfo = createDiagnosticForNode(func, Diagnostics.Did_you_mean_to_mark_this_function_as_async);
+                            addRelatedInfo(diagnostic, relatedInfo);
+                        }
+                        diagnostics.add(diagnostic);
+                        return true;
+                    }
+                    return false;
                 }
             }