From 7a19b66cc0ae44456b7c62a4c84b718d35777a7c Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Thu, 1 Mar 2018 16:01:32 -0800
Subject: [PATCH] Don't propagate 'never' types in type inference

---
 src/compiler/checker.ts | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ae91d887781..1931661bf5f 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -11525,10 +11525,10 @@ namespace ts {
                 if (!couldContainTypeVariables(target)) {
                     return;
                 }
-                if (source.flags & (TypeFlags.Any | TypeFlags.Never) && source !== silentNeverType) {
-                    // We are inferring from 'any' or 'never'. We want to infer this type for every type parameter
-                    // referenced in the target type, so we record the propagation type and infer from the target
-                    // to itself. Then, as we find candidates we substitute the propagation type.
+                if (source.flags & TypeFlags.Any) {
+                    // We are inferring from an 'any' type. We want to infer this type for every type parameter
+                    // referenced in the target type, so we record it as the propagation type and infer from the
+                    // target to itself. Then, as we find candidates we substitute the propagation type.
                     const savePropagationType = propagationType;
                     propagationType = source;
                     inferFromTypes(target, target);