forked from Fediversity/Fediversity
105 lines
3 KiB
JavaScript
105 lines
3 KiB
JavaScript
import {eat, finishToken, lookaheadTypeAndKeyword, match, nextTokenStart} from "../tokenizer/index";
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import {formatTokenType, TokenType as tt} from "../tokenizer/types";
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import {charCodes} from "../util/charcodes";
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import {input, state} from "./base";
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// ## Parser utilities
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// Tests whether parsed token is a contextual keyword.
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export function isContextual(contextualKeyword) {
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return state.contextualKeyword === contextualKeyword;
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}
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export function isLookaheadContextual(contextualKeyword) {
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const l = lookaheadTypeAndKeyword();
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return l.type === tt.name && l.contextualKeyword === contextualKeyword;
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}
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// Consumes contextual keyword if possible.
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export function eatContextual(contextualKeyword) {
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return state.contextualKeyword === contextualKeyword && eat(tt.name);
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}
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// Asserts that following token is given contextual keyword.
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export function expectContextual(contextualKeyword) {
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if (!eatContextual(contextualKeyword)) {
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unexpected();
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}
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}
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// Test whether a semicolon can be inserted at the current position.
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export function canInsertSemicolon() {
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return match(tt.eof) || match(tt.braceR) || hasPrecedingLineBreak();
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}
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export function hasPrecedingLineBreak() {
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const prevToken = state.tokens[state.tokens.length - 1];
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const lastTokEnd = prevToken ? prevToken.end : 0;
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for (let i = lastTokEnd; i < state.start; i++) {
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const code = input.charCodeAt(i);
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if (
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code === charCodes.lineFeed ||
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code === charCodes.carriageReturn ||
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code === 0x2028 ||
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code === 0x2029
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) {
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return true;
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}
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}
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return false;
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}
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export function hasFollowingLineBreak() {
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const nextStart = nextTokenStart();
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for (let i = state.end; i < nextStart; i++) {
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const code = input.charCodeAt(i);
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if (
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code === charCodes.lineFeed ||
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code === charCodes.carriageReturn ||
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code === 0x2028 ||
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code === 0x2029
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) {
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return true;
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}
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}
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return false;
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}
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export function isLineTerminator() {
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return eat(tt.semi) || canInsertSemicolon();
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}
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// Consume a semicolon, or, failing that, see if we are allowed to
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// pretend that there is a semicolon at this position.
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export function semicolon() {
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if (!isLineTerminator()) {
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unexpected('Unexpected token, expected ";"');
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}
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}
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// Expect a token of a given type. If found, consume it, otherwise,
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// raise an unexpected token error at given pos.
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export function expect(type) {
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const matched = eat(type);
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if (!matched) {
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unexpected(`Unexpected token, expected "${formatTokenType(type)}"`);
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}
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}
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/**
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* Transition the parser to an error state. All code needs to be written to naturally unwind in this
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* state, which allows us to backtrack without exceptions and without error plumbing everywhere.
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*/
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export function unexpected(message = "Unexpected token", pos = state.start) {
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if (state.error) {
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return;
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}
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// eslint-disable-next-line @typescript-eslint/no-explicit-any
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const err = new SyntaxError(message);
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err.pos = pos;
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state.error = err;
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state.pos = input.length;
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finishToken(tt.eof);
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}
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