remove mutables in favour of unified mutability tracking

src/compile/Component.ts

@@ -170,11 +170,6 @@ export default class Component {
 			// TODO remove this
 			this.props = props.map(name => ({ name, as: name }));
 		}
-
-		// tell the root fragment scope about all of the mutable names we know from the script
-		this.vars.forEach(variable => {
-			if (variable.mutated) this.fragment.scope.mutables.add(name);
-		});
 	}
 
 	add_var(variable: Var) {
@@ -933,7 +928,7 @@ export default class Component {
 
 		this.ast.instance.content.body.forEach(node => {
 			if (node.type === 'VariableDeclaration') {
-				if (node.declarations.every(d => d.init && d.init.type === 'Literal' && !this.var_lookup.get(d.id.name).mutated && !template_scope.containsMutable([d.id.name]))) {
+				if (node.declarations.every(d => d.init && d.init.type === 'Literal' && !this.var_lookup.get(d.id.name).mutated)) {
 					node.declarations.forEach(d => {
 						hoistable_names.add(d.id.name);
 					});

src/compile/nodes/shared/TemplateScope.ts

@@ -9,7 +9,6 @@ type NodeWithScope = EachBlock | ThenBlock | CatchBlock | InlineComponent | Elem
 export default class TemplateScope {
 	names: Set<string>;
 	dependenciesForName: Map<string, Set<string>>;
-	mutables: Set<string> = new Set();
 	owners: Map<string, NodeWithScope> = new Map();
 	parent?: TemplateScope;
 
@@ -31,21 +30,6 @@ export default class TemplateScope {
 		return child;
 	}
 
-	containsMutable(names: Iterable<string>) {
-		for (const name of names) {
-			const owner = this.getOwner(name);
-			const is_let = owner && (owner.type === 'InlineComponent' || owner.type === 'Element');
-			if (is_let) return true;
-
-			if (name[0] === '$') return true;
-			if (this.mutables.has(name)) return true;
-			else if (this.dependenciesForName.has(name) && this.containsMutable(this.dependenciesForName.get(name))) return true;
-		}
-
-		if (this.parent) return this.parent.containsMutable(names);
-		else return false;
-	}
-
 	isTopLevel(name: string) {
 		return !this.parent || !this.names.has(name) && this.parent.isTopLevel(name);
 	}