fix(isolated-declarations): preserve readonly literal initializers (#19177)

This is the cause of the current monitor oxc failure

TS's Behaviour:

![Screenshot 2026-02-09 at 12.18.51.png](https://app.graphite.com/user-attachments/assets/858f029d-5427-4593-95c1-ae5efd3239e1.png)

Us Before:

![Screenshot 2026-02-09 at 12.18.17.png](https://app.graphite.com/user-attachments/assets/a4df3235-e4cd-4526-b632-df7371181922.png)

Us After:

```
export declare class ReadonlyLiteralInitializers {

	readonly directTrue = true;
	readonly constAssertTrue = true;
	writableTrue: boolean;
}
```

crates/oxc_isolated_declarations/src/class.rs

@@ -104,8 +104,11 @@ impl<'a> IsolatedDeclarations<'a> {
                 type_annotation = property.type_annotation.clone_in(self.ast.allocator);
             } else if let Some(expr) = property.value.as_ref() {
                 let ts_type = if property.readonly {
-                    // `field = 'string'` remain `field = 'string'` instead of `field: 'string'`
-                    if Self::is_need_to_infer_type_from_expression(expr) {
+                    // Keep literal const initializers on readonly class properties to match TS d.ts emit.
+                    if let Some(initializer) = self.get_literal_const_initializer(expr) {
+                        value = Some(initializer);
+                        None
+                    } else if Self::is_need_to_infer_type_from_expression(expr) {
                         self.transform_expression_to_ts_type(expr)
                     } else {
                         if let Expression::TemplateLiteral(lit) = expr {
@@ -147,6 +150,31 @@ impl<'a> IsolatedDeclarations<'a> {
         )
     }
 
+    fn get_literal_const_initializer(&self, expr: &Expression<'a>) -> Option<Expression<'a>> {
+        match expr {
+            Expression::BooleanLiteral(_)
+            | Expression::NumericLiteral(_)
+            | Expression::BigIntLiteral(_)
+            | Expression::StringLiteral(_) => Some(expr.clone_in(self.ast.allocator)),
+            Expression::TemplateLiteral(lit) if lit.expressions.is_empty() => {
+                self.transform_template_to_string(lit).map(Expression::StringLiteral)
+            }
+            Expression::UnaryExpression(expr) if Self::can_infer_unary_expression(expr) => {
+                Some(Expression::UnaryExpression(expr.clone_in(self.ast.allocator)))
+            }
+            Expression::ParenthesizedExpression(expr) => {
+                self.get_literal_const_initializer(&expr.expression)
+            }
+            Expression::TSAsExpression(expr) if expr.type_annotation.is_const_type_reference() => {
+                self.get_literal_const_initializer(&expr.expression)
+            }
+            Expression::TSTypeAssertion(expr) if expr.type_annotation.is_const_type_reference() => {
+                self.get_literal_const_initializer(&expr.expression)
+            }
+            _ => None,
+        }
+    }
+
     fn transform_class_method_definition(
         &self,
         definition: &MethodDefinition<'a>,

crates/oxc_isolated_declarations/tests/fixtures/readonly-class-property-initializer.ts

@@ -0,0 +1,17 @@
+export class ReadonlyLiteralInitializers {
+  readonly directTrue = true;
+  readonly parenTrue = (true);
+  readonly constAssertTrue = true as const;
+  readonly nestedConstAssert = ((true as const));
+
+  readonly directString = "x";
+  readonly parenString = ("x");
+  readonly templateNoExpr = `x`;
+  readonly constAssertString = ("x" as const);
+
+  readonly unaryNumber = -1;
+  readonly unaryParenNumber = (-1);
+  readonly constAssertNumber = (1 as const);
+
+  writableTrue = true;
+}

crates/oxc_isolated_declarations/tests/fixtures/readonly-satisfies.ts

@@ -0,0 +1,3 @@
+export class ReadonlySatisfies {
+  readonly falseSatisfies = (false satisfies boolean);
+}

crates/oxc_isolated_declarations/tests/snapshots/readonly-class-property-initializer.snap

@@ -0,0 +1,21 @@
+---
+source: crates/oxc_isolated_declarations/tests/mod.rs
+input_file: crates/oxc_isolated_declarations/tests/fixtures/readonly-class-property-initializer.ts
+---
+```
+==================== .D.TS ====================
+
+export declare class ReadonlyLiteralInitializers {
+	readonly directTrue = true;
+	readonly parenTrue = true;
+	readonly constAssertTrue = true;
+	readonly nestedConstAssert = true;
+	readonly directString = "x";
+	readonly parenString = "x";
+	readonly templateNoExpr = "x";
+	readonly constAssertString = "x";
+	readonly unaryNumber = -1;
+	readonly unaryParenNumber = -1;
+	readonly constAssertNumber = 1;
+	writableTrue: boolean;
+}

crates/oxc_isolated_declarations/tests/snapshots/readonly-satisfies.snap

@@ -0,0 +1,25 @@
+---
+source: crates/oxc_isolated_declarations/tests/mod.rs
+input_file: crates/oxc_isolated_declarations/tests/fixtures/readonly-satisfies.ts
+---
+```
+==================== .D.TS ====================
+
+export declare class ReadonlySatisfies {
+	readonly falseSatisfies;
+}
+
+
+==================== Errors ====================
+
+  x TS9012: Property must have an explicit type annotation with
+  | --isolatedDeclarations.
+   ,-[2:12]
+ 1 | export class ReadonlySatisfies {
+ 2 |   readonly falseSatisfies = (false satisfies boolean);
+   :            ^^^^^^^^^^^^^^
+ 3 | }
+   `----
+
+
+```