refactor: _ParseAST.isAssignmentOperator to type guard

Update `_ParseAST.isAssignmentOperator` to type guard

packages/compiler/src/expression_parser/ast.ts

@@ -268,7 +268,17 @@ export class Interpolation extends AST {
   }
 }
 
-type AssignmentOperation = '=' | '+=' | '-=' | '*=' | '/=' | '%=' | '**=' | '&&=' | '||=' | '??=';
+export type AssignmentOperation =
+  | '='
+  | '+='
+  | '-='
+  | '*='
+  | '/='
+  | '%='
+  | '**='
+  | '&&='
+  | '||='
+  | '??=';
 type BinaryOperation =
   | AssignmentOperation
   // Logical

packages/compiler/src/expression_parser/parser.ts

@@ -56,6 +56,7 @@ import {
   Unary,
   VariableBinding,
   VoidExpression,
+  type AssignmentOperation,
 } from './ast';
 import {EOF, Lexer, StringTokenKind, Token, TokenType} from './lexer';
 export interface InterpolationPiece {
@@ -730,7 +731,10 @@ class _ParseAST {
     }
   }
 
-  private isAssignmentOperator(token: Token): boolean {
+  private isAssignmentOperator(token: Token): token is Token & {
+    type: typeof TokenType.Operator;
+    strValue: AssignmentOperation;
+  } {
     return token.type === TokenType.Operator && Binary.isAssignmentOperation(token.strValue);
   }