perf: introduce AST to avoid reparse

src/parser/parser.ts

@@ -1,13 +1,13 @@
 import { ParseError } from '../util/error'
 import { Liquid } from '../liquid'
 import { ParseStream } from './parse-stream'
-import { Token } from './token'
-import { TagToken } from './tag-token'
-import { OutputToken } from './output-token'
+import { isTagToken, isOutputToken } from '../util/type-guards'
+import { OutputToken } from '../tokens/output-token'
 import { Tag } from '../template/tag/tag'
 import { Output } from '../template/output'
 import { HTML } from '../template/html'
 import { Template } from '../template/template'
+import { TopLevelToken } from '../tokens/toplevel-token'
 
 export default class Parser {
   private liquid: Liquid
@@ -15,7 +15,7 @@ export default class Parser {
   public constructor (liquid: Liquid) {
     this.liquid = liquid
   }
-  public parse (tokens: Token[]) {
+  public parse (tokens: TopLevelToken[]) {
     let token
     const templates: Template[] = []
     while ((token = tokens.shift())) {
@@ -23,12 +23,12 @@ export default class Parser {
     }
     return templates
   }
-  public parseToken (token: Token, remainTokens: Token[]) {
+  public parseToken (token: TopLevelToken, remainTokens: TopLevelToken[]) {
     try {
-      if (TagToken.is(token)) {
+      if (isTagToken(token)) {
         return new Tag(token, remainTokens, this.liquid)
       }
-      if (OutputToken.is(token)) {
+      if (isOutputToken(token)) {
         return new Output(token as OutputToken, this.liquid.filters)
       }
       return new HTML(token)
@@ -36,7 +36,7 @@ export default class Parser {
       throw new ParseError(e, token)
     }
   }
-  public parseStream (tokens: Token[]) {
+  public parseStream (tokens: TopLevelToken[]) {
     return new ParseStream(tokens, (token, tokens) => this.parseToken(token, tokens))
   }
 }