From 082802e7a87ed37f9bb329fd963f8193218ef703 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Tue, 21 Nov 2017 13:17:32 -0800
Subject: [PATCH] JS:Treat type-annotated uninitialised vars as declarations

Currently only applies to property accesses, but maybe should apply to
everything.
---
 src/compiler/binder.ts    | 5 ++++-
 src/compiler/utilities.ts | 6 ++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index c9faefed23..dca168b4c0 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -2006,6 +2006,9 @@ namespace ts {
                     if (currentFlow && isNarrowableReference(<Expression>node)) {
                         node.flowNode = currentFlow;
                     }
+                    if (isSpecialPropertyDeclaration(node as PropertyAccessExpression)) {
+                        bindThisPropertyAssignment(node as PropertyAccessExpression);
+                    }
                     break;
                 case SyntaxKind.BinaryExpression:
                     const specialKind = getSpecialPropertyAssignmentKind(node as BinaryExpression);
@@ -2314,7 +2317,7 @@ namespace ts {
             declareSymbol(file.symbol.exports, file.symbol, node, SymbolFlags.Property | SymbolFlags.ExportValue | SymbolFlags.ValueModule, SymbolFlags.None);
         }
 
-        function bindThisPropertyAssignment(node: BinaryExpression) {
+        function bindThisPropertyAssignment(node: BinaryExpression | PropertyAccessExpression) {
             Debug.assert(isInJavaScriptFile(node));
             const container = getThisContainer(node, /*includeArrowFunctions*/ false);
             switch (container.kind) {
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index ac096174ab..f308403541 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -1508,6 +1508,12 @@ namespace ts {
         return SpecialPropertyAssignmentKind.None;
     }
 
+    export function isSpecialPropertyDeclaration(expr: ts.PropertyAccessExpression): boolean {
+        return isInJavaScriptFile(expr) &&
+            expr.parent && expr.parent.kind === SyntaxKind.ExpressionStatement &&
+            !!getJSDocTypeTag(expr.parent);
+    }
+
     export function getExternalModuleName(node: Node): Expression {
         if (node.kind === SyntaxKind.ImportDeclaration) {
             return (<ImportDeclaration>node).moduleSpecifier;