Fix TS2540 not reported for readonly properties accessed through imports (#2179)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: jakebailey <5341706+jakebailey@users.noreply.github.com>

Author: Copilot

internal/checker/checker.go

@@ -26600,11 +26600,6 @@ func (c *Checker) isAssignmentToReadonlyEntity(expr *ast.Node, symbol *ast.Symbo
 			if expressionSymbol.Flags&ast.SymbolFlagsModuleExports != 0 {
 				return false
 			}
-			// references through namespace import should be readonly
-			if expressionSymbol.Flags&ast.SymbolFlagsAlias != 0 {
-				declaration := c.getDeclarationOfAliasSymbol(expressionSymbol)
-				return declaration != nil && ast.IsNamespaceImport(declaration)
-			}
 		}
 	}
 	if c.isReadonlySymbol(symbol) {
@@ -26627,6 +26622,17 @@ func (c *Checker) isAssignmentToReadonlyEntity(expr *ast.Node, symbol *ast.Symbo
 		}
 		return true
 	}
+	if ast.IsAccessExpression(expr) {
+		// references through namespace import should be readonly
+		node := ast.SkipParentheses(expr.Expression())
+		if ast.IsIdentifier(node) {
+			expressionSymbol := c.getResolvedSymbol(node)
+			if expressionSymbol.Flags&ast.SymbolFlagsAlias != 0 {
+				declaration := c.getDeclarationOfAliasSymbol(expressionSymbol)
+				return declaration != nil && ast.IsNamespaceImport(declaration)
+			}
+		}
+	}
 	return false
 }
 

testdata/baselines/reference/compiler/readonlyDefaultExport.errors.txt

@@ -0,0 +1,17 @@
+b.ts(3,5): error TS2540: Cannot assign to 'a' because it is a read-only property.
+
+
+==== a.ts (0 errors) ====
+    const foo = {
+      a: 1
+    }
+    
+    export default foo as Readonly<typeof foo>
+    
+==== b.ts (1 errors) ====
+    import foo from './a'
+    
+    foo.a = 2
+        ~
+!!! error TS2540: Cannot assign to 'a' because it is a read-only property.
+    

testdata/baselines/reference/compiler/readonlyDefaultExport.js

@@ -0,0 +1,30 @@
+//// [tests/cases/compiler/readonlyDefaultExport.ts] ////
+
+//// [a.ts]
+const foo = {
+  a: 1
+}
+
+export default foo as Readonly<typeof foo>
+
+//// [b.ts]
+import foo from './a'
+
+foo.a = 2
+
+
+//// [a.js]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+const foo = {
+    a: 1
+};
+exports.default = foo;
+//// [b.js]
+"use strict";
+var __importDefault = (this && this.__importDefault) || function (mod) {
+    return (mod && mod.__esModule) ? mod : { "default": mod };
+};
+Object.defineProperty(exports, "__esModule", { value: true });
+const a_1 = __importDefault(require("./a"));
+a_1.default.a = 2;

testdata/baselines/reference/compiler/readonlyDefaultExport.symbols

@@ -0,0 +1,24 @@
+//// [tests/cases/compiler/readonlyDefaultExport.ts] ////
+
+=== a.ts ===
+const foo = {
+>foo : Symbol(foo, Decl(a.ts, 0, 5))
+
+  a: 1
+>a : Symbol(a, Decl(a.ts, 0, 13))
+}
+
+export default foo as Readonly<typeof foo>
+>foo : Symbol(foo, Decl(a.ts, 0, 5))
+>Readonly : Symbol(Readonly, Decl(lib.es5.d.ts, --, --))
+>foo : Symbol(foo, Decl(a.ts, 0, 5))
+
+=== b.ts ===
+import foo from './a'
+>foo : Symbol(foo, Decl(b.ts, 0, 6))
+
+foo.a = 2
+>foo.a : Symbol(a, Decl(a.ts, 0, 13))
+>foo : Symbol(foo, Decl(b.ts, 0, 6))
+>a : Symbol(a, Decl(a.ts, 0, 13))
+

testdata/baselines/reference/compiler/readonlyDefaultExport.types

@@ -0,0 +1,28 @@
+//// [tests/cases/compiler/readonlyDefaultExport.ts] ////
+
+=== a.ts ===
+const foo = {
+>foo : { a: number; }
+>{  a: 1} : { a: number; }
+
+  a: 1
+>a : number
+>1 : 1
+}
+
+export default foo as Readonly<typeof foo>
+>foo as Readonly<typeof foo> : Readonly<{ a: number; }>
+>foo : { a: number; }
+>foo : { a: number; }
+
+=== b.ts ===
+import foo from './a'
+>foo : Readonly<{ a: number; }>
+
+foo.a = 2
+>foo.a = 2 : 2
+>foo.a : any
+>foo : Readonly<{ a: number; }>
+>a : any
+>2 : 2
+

testdata/baselines/reference/submodule/compiler/constDeclarations-access5.errors.txt

@@ -1,33 +1,84 @@
-constDeclarations_access_2.ts(4,1): error TS2322: Type '1' is not assignable to type '0'.
+constDeclarations_access_2.ts(4,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(5,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(6,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(7,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(8,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(9,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(10,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(11,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(12,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(13,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(14,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(15,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(17,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(18,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(19,5): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(20,5): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(22,7): error TS2540: Cannot assign to 'x' because it is a read-only property.
+constDeclarations_access_2.ts(24,3): error TS2540: Cannot assign to 'x' because it is a read-only property.
 
 
-==== constDeclarations_access_2.ts (1 errors) ====
+==== constDeclarations_access_2.ts (18 errors) ====
     ///<reference path='constDeclarations_access_1.ts'/>
     import m = require('./constDeclarations_access_1');
     // Errors
     m.x = 1;
-    ~~~
-!!! error TS2322: Type '1' is not assignable to type '0'.
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     m.x += 2;
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     m.x -= 3;
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     m.x *= 4;
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     m.x /= 5;
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     m.x %= 6;
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     m.x <<= 7;
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     m.x >>= 8;
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     m.x >>>= 9;
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     m.x &= 10;
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     m.x |= 11;
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     m.x ^= 12;
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     m
     m.x++;
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     m.x--;
+      ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     ++m.x;
+        ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
     --m.x;
+        ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
 
     ++((m.x));
+          ~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
 
     m["x"] = 0;
+      ~~~
+!!! error TS2540: Cannot assign to 'x' because it is a read-only property.
 
     // OK
     var a = m.x + 1;