chore: make Binding a class (#15359)

* chore: make Binding a class

* reorder

* regenerate

Author: Rich-Harris

packages/svelte/src/compiler/phases/scope.js

@@ -1,6 +1,6 @@
 /** @import { ClassDeclaration, Expression, FunctionDeclaration, Identifier, ImportDeclaration, MemberExpression, Node, Pattern, VariableDeclarator } from 'estree' */
 /** @import { Context, Visitor } from 'zimmerframe' */
-/** @import { AST, Binding, DeclarationKind } from '#compiler' */
+/** @import { AST, BindingKind, DeclarationKind } from '#compiler' */
 import is_reference from 'is-reference';
 import { walk } from 'zimmerframe';
 import { create_expression_metadata } from './nodes.js';
@@ -16,6 +16,69 @@ import { is_reserved, is_rune } from '../../utils.js';
 import { determine_slot } from '../utils/slot.js';
 import { validate_identifier_name } from './2-analyze/visitors/shared/utils.js';
 
+export class Binding {
+	/** @type {Scope} */
+	scope;
+
+	/** @type {Identifier} */
+	node;
+
+	/** @type {BindingKind} */
+	kind;
+
+	/** @type {DeclarationKind} */
+	declaration_kind;
+
+	/**
+	 * What the value was initialized with.
+	 * For destructured props such as `let { foo = 'bar' } = $props()` this is `'bar'` and not `$props()`
+	 * @type {null | Expression | FunctionDeclaration | ClassDeclaration | ImportDeclaration | AST.EachBlock | AST.SnippetBlock}
+	 */
+	initial;
+
+	/** @type {Array<{ node: Identifier; path: AST.SvelteNode[] }>} */
+	references = [];
+
+	/**
+	 * For `legacy_reactive`: its reactive dependencies
+	 * @type {Binding[]}
+	 */
+	legacy_dependencies = [];
+
+	/**
+	 * Legacy props: the `class` in `{ export klass as class}`. $props(): The `class` in { class: klass } = $props()
+	 * @type {string | null}
+	 */
+	prop_alias = null;
+
+	/**
+	 * Additional metadata, varies per binding type
+	 * @type {null | { inside_rest?: boolean }}
+	 */
+	metadata = null;
+
+	is_called = false;
+	mutated = false;
+	reassigned = false;
+	updated = false;
+
+	/**
+	 *
+	 * @param {Scope} scope
+	 * @param {Identifier} node
+	 * @param {BindingKind} kind
+	 * @param {DeclarationKind} declaration_kind
+	 * @param {Binding['initial']} initial
+	 */
+	constructor(scope, node, kind, declaration_kind, initial) {
+		this.scope = scope;
+		this.node = node;
+		this.initial = initial;
+		this.kind = kind;
+		this.declaration_kind = declaration_kind;
+	}
+}
+
 export class Scope {
 	/** @type {ScopeRoot} */
 	root;
@@ -100,22 +163,7 @@ export class Scope {
 			e.declaration_duplicate(node, node.name);
 		}
 
-		/** @type {Binding} */
-		const binding = {
-			node,
-			references: [],
-			legacy_dependencies: [],
-			initial,
-			reassigned: false,
-			mutated: false,
-			updated: false,
-			scope: this,
-			kind,
-			declaration_kind,
-			is_called: false,
-			prop_alias: null,
-			metadata: null
-		};
+		const binding = new Binding(this, node, kind, declaration_kind, initial);
 
 		validate_identifier_name(binding, this.function_depth);
 

packages/svelte/src/compiler/types/index.d.ts

@@ -1,12 +1,5 @@
-import type {
-	ClassDeclaration,
-	Expression,
-	FunctionDeclaration,
-	Identifier,
-	ImportDeclaration
-} from 'estree';
 import type { SourceMap } from 'magic-string';
-import type { Scope } from '../phases/scope.js';
+import type { Binding } from '../phases/scope.js';
 import type { AST, Namespace } from './template.js';
 import type { ICompileDiagnostic } from '../utils/compile_diagnostic.js';
 
@@ -241,6 +234,20 @@ export type ValidatedCompileOptions = ValidatedModuleCompileOptions &
 		hmr: CompileOptions['hmr'];
 	};
 
+export type BindingKind =
+	| 'normal' // A variable that is not in any way special
+	| 'prop' // A normal prop (possibly reassigned or mutated)
+	| 'bindable_prop' // A prop one can `bind:` to (possibly reassigned or mutated)
+	| 'rest_prop' // A rest prop
+	| 'raw_state' // A state variable
+	| 'state' // A deeply reactive state variable
+	| 'derived' // A derived variable
+	| 'each' // An each block parameter
+	| 'snippet' // A snippet parameter
+	| 'store_sub' // A $store value
+	| 'legacy_reactive' // A `$:` declaration
+	| 'template'; // A binding declared in the template, e.g. in an `await` block or `const` tag
+
 export type DeclarationKind =
 	| 'var'
 	| 'let'
@@ -251,66 +258,6 @@ export type DeclarationKind =
 	| 'rest_param'
 	| 'synthetic';
 
-export interface Binding {
-	node: Identifier;
-	/**
-	 * - `normal`: A variable that is not in any way special
-	 * - `prop`: A normal prop (possibly reassigned or mutated)
-	 * - `bindable_prop`: A prop one can `bind:` to (possibly reassigned or mutated)
-	 * - `rest_prop`: A rest prop
-	 * - `state`: A state variable
-	 * - `derived`: A derived variable
-	 * - `each`: An each block parameter
-	 * - `snippet`: A snippet parameter
-	 * - `store_sub`: A $store value
-	 * - `legacy_reactive`: A `$:` declaration
-	 * - `template`: A binding declared in the template, e.g. in an `await` block or `const` tag
-	 */
-	kind:
-		| 'normal'
-		| 'prop'
-		| 'bindable_prop'
-		| 'rest_prop'
-		| 'state'
-		| 'raw_state'
-		| 'derived'
-		| 'each'
-		| 'snippet'
-		| 'store_sub'
-		| 'legacy_reactive'
-		| 'template'
-		| 'snippet';
-	declaration_kind: DeclarationKind;
-	/**
-	 * What the value was initialized with.
-	 * For destructured props such as `let { foo = 'bar' } = $props()` this is `'bar'` and not `$props()`
-	 */
-	initial:
-		| null
-		| Expression
-		| FunctionDeclaration
-		| ClassDeclaration
-		| ImportDeclaration
-		| AST.EachBlock
-		| AST.SnippetBlock;
-	is_called: boolean;
-	references: { node: Identifier; path: AST.SvelteNode[] }[];
-	mutated: boolean;
-	reassigned: boolean;
-	/** `true` if mutated _or_ reassigned */
-	updated: boolean;
-	scope: Scope;
-	/** For `legacy_reactive`: its reactive dependencies */
-	legacy_dependencies: Binding[];
-	/** Legacy props: the `class` in `{ export klass as class}`. $props(): The `class` in { class: klass } = $props() */
-	prop_alias: string | null;
-	/** Additional metadata, varies per binding type */
-	metadata: {
-		/** `true` if is (inside) a rest parameter */
-		inside_rest?: boolean;
-	} | null;
-}
-
 export interface ExpressionMetadata {
 	/** All the bindings that are referenced inside this expression */
 	dependencies: Set<Binding>;
@@ -322,5 +269,7 @@ export interface ExpressionMetadata {
 
 export * from './template.js';
 
+export { Binding, Scope } from '../phases/scope.js';
+
 // TODO this chain is a bit weird
 export { ReactiveStatement } from '../phases/types.js';

packages/svelte/types/index.d.ts

@@ -622,8 +622,8 @@ declare module 'svelte/animate' {
 }
 
 declare module 'svelte/compiler' {
-	import type { Expression, Identifier, ArrayExpression, ArrowFunctionExpression, VariableDeclaration, VariableDeclarator, MemberExpression, Node, ObjectExpression, Pattern, Program, ChainExpression, SimpleCallExpression, SequenceExpression } from 'estree';
 	import type { SourceMap } from 'magic-string';
+	import type { ArrayExpression, ArrowFunctionExpression, VariableDeclaration, VariableDeclarator, Expression, Identifier, MemberExpression, Node, ObjectExpression, Pattern, Program, ChainExpression, SimpleCallExpression, SequenceExpression } from 'estree';
 	import type { Location } from 'locate-character';
 	/**
 	 * `compile` converts your `.svelte` source code into a JavaScript module that exports a component