From d2341e3f2977088d09a6f0063960a3d40d245cdf Mon Sep 17 00:00:00 2001
From: andre-fajar-n <andrenugroho395@gmail.com>
Date: Sun, 11 Oct 2026 08:44:36 +0700
Subject: [PATCH] fix: Fix nil pointer panic in getLateBoundSymbol under
 --noCheck

---
 tsc/internal/checker/checker.go                 | 12 ++++++++----
 .../noCheckExpandoElementAccessAssignment.js    | 16 ++++++++++++++++
 ...oCheckExpandoElementAccessAssignment.symbols | 13 +++++++++++++
 .../noCheckExpandoElementAccessAssignment.types | 17 +++++++++++++++++
 .../noCheckExpandoElementAccessAssignment.ts    |  8 ++++++++
 5 files changed, 62 insertions(+), 4 deletions(-)
 create mode 100644 tsc/testdata/baselines/reference/compiler/noCheckExpandoElementAccessAssignment.js
 create mode 100644 tsc/testdata/baselines/reference/compiler/noCheckExpandoElementAccessAssignment.symbols
 create mode 100644 tsc/testdata/baselines/reference/compiler/noCheckExpandoElementAccessAssignment.types
 create mode 100644 tsc/testdata/tests/cases/compiler/noCheckExpandoElementAccessAssignment.ts

diff --git a/tsc/internal/checker/checker.go b/tsc/internal/checker/checker.go
index 345ea00ce1437..b9208e3fb4ebd 100644
--- a/tsc/internal/checker/checker.go
+++ b/tsc/internal/checker/checker.go
@@ -14691,10 +14691,14 @@ func (c *Checker) getLateBoundSymbol(symbol *ast.Symbol) *ast.Symbol {
 	if links.lateSymbol == nil && core.Some(symbol.Declarations(), c.hasLateBindableName) {
 		// force late binding of members/exports. This will set the late-bound symbol
 		parent := c.getMergedSymbol(symbol.Parent())
-		if core.Some(symbol.Declarations(), ast.HasStaticModifier) {
-			c.getExportsOfSymbol(parent)
-		} else {
-			c.getMembersOfSymbol(parent)
+		// Parent can be nil for top-level script expandos (SourceFile has no symbol) when
+		// checking was skipped (--noCheck) and late binding has not run yet.
+		if parent != nil {
+			if core.Some(symbol.Declarations(), ast.HasStaticModifier) {
+				c.getExportsOfSymbol(parent)
+			} else {
+				c.getMembersOfSymbol(parent)
+			}
 		}
 	}
 	if links.lateSymbol == nil {
diff --git a/tsc/testdata/baselines/reference/compiler/noCheckExpandoElementAccessAssignment.js b/tsc/testdata/baselines/reference/compiler/noCheckExpandoElementAccessAssignment.js
new file mode 100644
index 0000000000000..0b1f387e18dfc
--- /dev/null
+++ b/tsc/testdata/baselines/reference/compiler/noCheckExpandoElementAccessAssignment.js
@@ -0,0 +1,16 @@
+//// [tests/cases/compiler/noCheckExpandoElementAccessAssignment.ts] ////
+
+//// [noCheckExpandoElementAccessAssignment.ts]
+const k = "bar";
+foo[k] = 1;
+function foo() {}
+
+
+
+
+//// [noCheckExpandoElementAccessAssignment.d.ts]
+declare const k = "bar";
+declare function foo(): void;
+declare namespace foo {
+    var bar: number;
+}
diff --git a/tsc/testdata/baselines/reference/compiler/noCheckExpandoElementAccessAssignment.symbols b/tsc/testdata/baselines/reference/compiler/noCheckExpandoElementAccessAssignment.symbols
new file mode 100644
index 0000000000000..6915aec55afa0
--- /dev/null
+++ b/tsc/testdata/baselines/reference/compiler/noCheckExpandoElementAccessAssignment.symbols
@@ -0,0 +1,13 @@
+//// [tests/cases/compiler/noCheckExpandoElementAccessAssignment.ts] ////
+
+=== noCheckExpandoElementAccessAssignment.ts ===
+const k = "bar";
+>k : Symbol(k, Decl(noCheckExpandoElementAccessAssignment.ts, 0, 5))
+
+foo[k] = 1;
+>foo : Symbol(foo, Decl(noCheckExpandoElementAccessAssignment.ts, 1, 11))
+>k : Symbol(k, Decl(noCheckExpandoElementAccessAssignment.ts, 0, 5))
+
+function foo() {}
+>foo : Symbol(foo, Decl(noCheckExpandoElementAccessAssignment.ts, 1, 11))
+
diff --git a/tsc/testdata/baselines/reference/compiler/noCheckExpandoElementAccessAssignment.types b/tsc/testdata/baselines/reference/compiler/noCheckExpandoElementAccessAssignment.types
new file mode 100644
index 0000000000000..4dbd3c67ddde0
--- /dev/null
+++ b/tsc/testdata/baselines/reference/compiler/noCheckExpandoElementAccessAssignment.types
@@ -0,0 +1,17 @@
+//// [tests/cases/compiler/noCheckExpandoElementAccessAssignment.ts] ////
+
+=== noCheckExpandoElementAccessAssignment.ts ===
+const k = "bar";
+>k : "bar"
+>"bar" : "bar"
+
+foo[k] = 1;
+>foo[k] = 1 : 1
+>foo[k] : number
+>foo : { (): void; bar: number; }
+>k : "bar"
+>1 : 1
+
+function foo() {}
+>foo : { (): void; bar: number; }
+
diff --git a/tsc/testdata/tests/cases/compiler/noCheckExpandoElementAccessAssignment.ts b/tsc/testdata/tests/cases/compiler/noCheckExpandoElementAccessAssignment.ts
new file mode 100644
index 0000000000000..5cf68fc81395b
--- /dev/null
+++ b/tsc/testdata/tests/cases/compiler/noCheckExpandoElementAccessAssignment.ts
@@ -0,0 +1,8 @@
+// @target: es2015
+// @noCheck: true
+// @emitDeclarationOnly: true
+// @declaration: true
+
+const k = "bar";
+foo[k] = 1;
+function foo() {}