From 68875dc5c87399b36bf27f3fe038f19d58dbcc0c Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Mon, 14 May 2018 14:58:35 -0700
Subject: [PATCH] JS initializers use original valueDecl, not mutated

target's valueDeclaration is set to the source's if it is not present.
This makes it incorrect to use getJSInitializerSymbol because it relies
on the symbol's valueDeclaration.

This fix just saves the original valueDeclaration before mutating and
uses that.
---
 src/compiler/checker.ts | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 0b0668dc5a0..fb326b7f388 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -871,6 +871,8 @@ namespace ts {
         function mergeSymbol(target: Symbol, source: Symbol) {
             if (!(target.flags & getExcludedSymbolFlags(source.flags)) ||
                 (source.flags | target.flags) & SymbolFlags.JSContainer) {
+                const targetValueDeclaration = target.valueDeclaration;
+                Debug.assert(!!(target.flags & SymbolFlags.Transient));
                 // Javascript static-property-assignment declarations always merge, even though they are also values
                 if (source.flags & SymbolFlags.ValueModule && target.flags & SymbolFlags.ValueModule && target.constEnumOnlyModule && !source.constEnumOnlyModule) {
                     // reset flag when merging instantiated module into value module that has only const enums
@@ -894,7 +896,8 @@ namespace ts {
                 }
                 if ((source.flags | target.flags) & SymbolFlags.JSContainer) {
                     const sourceInitializer = getJSInitializerSymbol(source);
-                    let targetInitializer = getJSInitializerSymbol(target);
+                    const init = getDeclaredJavascriptInitializer(targetValueDeclaration) || getAssignedJavascriptInitializer(targetValueDeclaration);
+                    let targetInitializer = init && init.symbol ? init.symbol : target;
                     if (sourceInitializer !== source || targetInitializer !== target) {
                         if (!(targetInitializer.flags & SymbolFlags.Transient)) {
                             const mergedInitializer = getMergedSymbol(targetInitializer);