From 8f8a579eee719bd2c95c7a0b0e27de4f0bdc14aa Mon Sep 17 00:00:00 2001
From: Armando Aguirre <armanio123@gmail.com>
Date: Wed, 31 Mar 2021 18:18:16 -0700
Subject: [PATCH] Added BindingElement to isSomeImportDeclaration (#43387)

* Added BindingElement to isSomeImportDeclaration

* Added tests

* Refactores to use getDeclarationOfAlias
---
 src/compiler/checker.ts                       | 18 ++------------
 ...onJsImportBindingElementNarrowType.symbols | 20 ++++++++++++++++
 ...mmonJsImportBindingElementNarrowType.types | 24 +++++++++++++++++++
 .../commonJsImportBindingElementNarrowType.ts | 15 ++++++++++++
 4 files changed, 61 insertions(+), 16 deletions(-)
 create mode 100644 tests/baselines/reference/commonJsImportBindingElementNarrowType.symbols
 create mode 100644 tests/baselines/reference/commonJsImportBindingElementNarrowType.types
 create mode 100644 tests/cases/conformance/externalModules/commonJsImportBindingElementNarrowType.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 726690dd48f..4201853d856 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -2489,6 +2489,7 @@ namespace ts {
          * module.exports = <EntityNameExpression>
          * {<Identifier>}
          * {name: <EntityNameExpression>}
+         * const { x } = require ...
          */
         function isAliasSymbolDeclaration(node: Node): boolean {
             return node.kind === SyntaxKind.ImportEqualsDeclaration
@@ -23933,7 +23934,7 @@ namespace ts {
                 }
             }
             else if (isAlias) {
-                declaration = symbol.declarations?.find(isSomeImportDeclaration);
+                declaration = getDeclarationOfAliasSymbol(symbol);
             }
             else {
                 return type;
@@ -41950,21 +41951,6 @@ namespace ts {
         }
     }
 
-    function isSomeImportDeclaration(decl: Node): boolean {
-        switch (decl.kind) {
-            case SyntaxKind.ImportClause: // For default import
-            case SyntaxKind.ImportEqualsDeclaration:
-            case SyntaxKind.NamespaceImport:
-            case SyntaxKind.ImportSpecifier: // For rename import `x as y`
-                return true;
-            case SyntaxKind.Identifier:
-                // For regular import, `decl` is an Identifier under the ImportSpecifier.
-                return decl.parent.kind === SyntaxKind.ImportSpecifier;
-            default:
-                return false;
-        }
-    }
-
     namespace JsxNames {
         export const JSX = "JSX" as __String;
         export const IntrinsicElements = "IntrinsicElements" as __String;
diff --git a/tests/baselines/reference/commonJsImportBindingElementNarrowType.symbols b/tests/baselines/reference/commonJsImportBindingElementNarrowType.symbols
new file mode 100644
index 00000000000..4410ae92d6a
--- /dev/null
+++ b/tests/baselines/reference/commonJsImportBindingElementNarrowType.symbols
@@ -0,0 +1,20 @@
+=== /bar.js ===
+const { a } = require("./foo");
+>a : Symbol(a, Decl(bar.js, 0, 7))
+>require : Symbol(require)
+>"./foo" : Symbol("/foo", Decl(foo.d.ts, 0, 0))
+
+if (a) {
+>a : Symbol(a, Decl(bar.js, 0, 7))
+
+  var x = a + 1;
+>x : Symbol(x, Decl(bar.js, 2, 5))
+>a : Symbol(a, Decl(bar.js, 0, 7))
+}
+=== /foo.d.ts ===
+// Regresion test for GH#41957
+
+
+export const a: number | null;
+>a : Symbol(a, Decl(foo.d.ts, 3, 12))
+
diff --git a/tests/baselines/reference/commonJsImportBindingElementNarrowType.types b/tests/baselines/reference/commonJsImportBindingElementNarrowType.types
new file mode 100644
index 00000000000..6eff02b733f
--- /dev/null
+++ b/tests/baselines/reference/commonJsImportBindingElementNarrowType.types
@@ -0,0 +1,24 @@
+=== /bar.js ===
+const { a } = require("./foo");
+>a : number | null
+>require("./foo") : typeof import("/foo")
+>require : any
+>"./foo" : "./foo"
+
+if (a) {
+>a : number | null
+
+  var x = a + 1;
+>x : number
+>a + 1 : number
+>a : number
+>1 : 1
+}
+=== /foo.d.ts ===
+// Regresion test for GH#41957
+
+
+export const a: number | null;
+>a : number | null
+>null : null
+
diff --git a/tests/cases/conformance/externalModules/commonJsImportBindingElementNarrowType.ts b/tests/cases/conformance/externalModules/commonJsImportBindingElementNarrowType.ts
new file mode 100644
index 00000000000..a98fdc3ef67
--- /dev/null
+++ b/tests/cases/conformance/externalModules/commonJsImportBindingElementNarrowType.ts
@@ -0,0 +1,15 @@
+// Regresion test for GH#41957
+
+// @allowJs: true
+// @checkJs: true
+// @strictNullChecks: true
+// @noEmit: true
+
+// @Filename: /foo.d.ts
+export const a: number | null;
+
+// @Filename: /bar.js
+const { a } = require("./foo");
+if (a) {
+  var x = a + 1;
+}
\ No newline at end of file