Handle JSDoc tags on 'this' properties

Author: RyanCavanaugh

src/compiler/checker.ts

@@ -2937,6 +2937,14 @@ namespace ts {
                 }
                 // Handle module.exports = expr
                 if (declaration.kind === SyntaxKind.BinaryExpression) {
+                    // Use JS Doc type if present on parent expression statement
+                    if (declaration.flags & NodeFlags.JavaScriptFile) {
+                        const typeTag = getJSDocTypeTag(declaration.parent);
+                        if (typeTag && typeTag.typeExpression) {
+                            return links.type = getTypeFromTypeNode(typeTag.typeExpression.type);
+                        }
+                    }
+
                     return links.type = getUnionType(map(symbol.declarations, (decl: BinaryExpression) => checkExpressionCached(decl.right)));
                 }
                 if (declaration.kind === SyntaxKind.PropertyAccessExpression) {