fix: Fix nil pointer panic in getLateBoundSymbol under --noCheck

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 {

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;
+}

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))
+

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; }
+

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() {}