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