From d8ce7d72a92cc76ee3e6be57136439d3d980acd2 Mon Sep 17 00:00:00 2001
From: Ryan Cavanaugh <RyanCavanaugh@users.noreply.github.com>
Date: Tue, 25 Feb 2020 11:09:32 -0800
Subject: [PATCH] Check for undefined `source.symbol`

Fixes #37014
---
 src/compiler/checker.ts                                      | 1 +
 tests/cases/compiler/privateFieldAssignabilityFromUnknown.ts | 5 +++++
 2 files changed, 6 insertions(+)
 create mode 100644 tests/cases/compiler/privateFieldAssignabilityFromUnknown.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index a1a0b598231b7..b92c95b14d12c 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -16239,6 +16239,7 @@ namespace ts {
                 if (unmatchedProperty.valueDeclaration
                     && isNamedDeclaration(unmatchedProperty.valueDeclaration)
                     && isPrivateIdentifier(unmatchedProperty.valueDeclaration.name)
+                    && source.symbol
                     && source.symbol.flags & SymbolFlags.Class) {
                     const privateIdentifierDescription = unmatchedProperty.valueDeclaration.name.escapedText;
                     const symbolTableKey = getSymbolNameForPrivateIdentifier(source.symbol, privateIdentifierDescription);
diff --git a/tests/cases/compiler/privateFieldAssignabilityFromUnknown.ts b/tests/cases/compiler/privateFieldAssignabilityFromUnknown.ts
new file mode 100644
index 0000000000000..09f8cf460ed29
--- /dev/null
+++ b/tests/cases/compiler/privateFieldAssignabilityFromUnknown.ts
@@ -0,0 +1,5 @@
+export class Class {
+  #field: any
+}
+
+const task: Class = {} as unknown;