Use readonly fields for type meta data

Author: msujew

packages/langium/src/syntax-tree.ts

@@ -257,39 +257,39 @@ export abstract class AbstractAstReflection implements AstReflection {
  * A map of all AST node types and their meta data.
  */
 export interface AstMetaData {
- [type: string]: TypeMetaData
+ readonly [type: string]: TypeMetaData
 }
 
 /**
  * Represents runtime meta data about an AST node type.
  */
 export interface TypeMetaData {
  /** The name of this AST node type. Corresponds to the `AstNode.$type` value. */
- name: string
+ readonly name: string
  /** A list of properties with their relevant meta data. */
- properties: {
- [name: string]: PropertyMetaData
+ readonly properties: {
+ readonly [name: string]: PropertyMetaData
  }
  /** The super types of this AST node type. */
- superTypes: string[]
+ readonly superTypes: readonly string[]
 }
 
 /**
  * Describes the meta data of a property of an AST node.
  */
 export interface PropertyMetaData {
  /** The name of this property. */
- name: string
+ readonly name: string
  /**
  * Indicates that the property is mandatory in the AST node.
  * For example, if an AST node contains an array, but no elements of this array have been parsed,
  * we still expect an empty array instead of `undefined`.
  */
- defaultValue?: PropertyType
+ readonly defaultValue?: PropertyType
  /**
  * If the property is a reference, this is the type of the reference target.
  */
- referenceType?: string
+ readonly referenceType?: string
 }
 
 /**