check most local scopes first

src/compiler/compile/Component.ts

@@ -789,7 +789,7 @@ export default class Component {
 				}
 
 				let deep = false;
-				let names: string[] | null;
+				let names: string[] | undefined; 
 
 				if (node.type === 'AssignmentExpression') {
 						deep = node.left.type === 'MemberExpression';
@@ -804,8 +804,18 @@ export default class Component {
 
 				if (names) {
 					names.forEach(name => {
-						const variable = component.var_lookup.get(name);
-						if (variable && variable.writable === false && !deep) {
+						let current_scope = scope;
+						let declaration;
+
+						while (current_scope) {
+							if (current_scope.declarations.has(name)) {
+								declaration = current_scope.declarations.get(name);
+								break;
+							}
+							current_scope = current_scope.parent;
+						}
+
+						if (declaration && declaration.kind === 'const' && !deep) {
 							component.error(node as any, {
 								code: 'assignment-to-const',
 								message: 'You are assigning to a const'

src/compiler/compile/nodes/shared/Expression.ts

@@ -151,13 +151,29 @@ export default class Expression {
 
 							if (variable) {
 								variable[deep ? 'mutated' : 'reassigned'] = true;
+							}
+
+							let current_scope = scope;
+							let declaration;
 
-								if (!deep && variable.writable === false) {
-									component.error(node as any, {
-										code: 'assignment-to-const',
-										message: 'You are assigning to a const'
-									});
+							while (current_scope) {
+								if (current_scope.declarations.has(name)) {
+									declaration = current_scope.declarations.get(name);
+									break;
 								}
+								current_scope = current_scope.parent;
+							}
+
+							if (declaration && declaration.kind === 'const' && !deep) {
+								component.error(node as any, {
+									code: 'assignment-to-const',
+									message: 'You are assigning to a const'
+								});
+							} else if (variable && variable.writable === false && !deep) {
+								component.error(node as any, {
+									code: 'assignment-to-const',
+									message: 'You are assigning to a const'
+								});
 							}
 						}
 					});