From b0143bb4464b88cd4fb4aded467bc8848edc9d84 Mon Sep 17 00:00:00 2001
From: uhyo <uhyo@uhy.ooo>
Date: Thu, 2 May 2019 01:09:29 +0900
Subject: [PATCH] add relatedInfo to error message for 'await' used in
 non-async function

---
 src/compiler/checker.ts              | 15 ++++++++++++++-
 src/compiler/diagnosticMessages.json |  6 +++++-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 978970927313f..2ae614b2dd8f1 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -23087,7 +23087,20 @@ namespace ts {
             // Grammar checking
             if (produceDiagnostics) {
                 if (!(node.flags & NodeFlags.AwaitContext)) {
-                    grammarErrorOnFirstToken(node, Diagnostics.await_expression_is_only_allowed_within_an_async_function);
+                    // use of 'await' in non-async function
+                    const sourceFile = getSourceFileOfNode(node);
+                    if (!hasParseDiagnostics(sourceFile)) {
+                        const span = getSpanOfTokenAtPosition(sourceFile, node.pos);
+                        const diagnostic = createFileDiagnostic(sourceFile, span.start, span.length, Diagnostics.await_expression_is_only_allowed_within_an_async_function);
+                        const func = getContainingFunction(node);
+                        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);
+                    }
                 }
 
                 if (isInParameterInitializerBeforeContainingFunction(node)) {
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 75a21022adbe9..8342a4dd6c4d5 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1035,6 +1035,10 @@
         "category": "Error",
         "code": 1355
     },
+    "Did you mean to mark this function as 'async'?": {
+        "category": "Error",
+        "code": 1356
+    },
 
     "Duplicate identifier '{0}'.": {
         "category": "Error",
@@ -2959,7 +2963,7 @@
         "category": "Error",
         "code": 4104
     },
-    
+
     "The current host does not support the '{0}' option.": {
         "category": "Error",
         "code": 5001