parser.ParseFile hangs when parsing "`"

[mrduncan]

I'm not entirely sure what's happening but calls to parser.ParseFile with a source of "`" seem to hang instead of returning an error.

A few cases I've tried:

"`"  // hangs
" `" // hangs
"` " // returns error

package main

import "github.com/dop251/goja/parser"

func main() {
	parser.ParseFile(nil, "", "`", 0)
}

goroutine 1 [runnable]:
github.com/dop251/goja/parser.(*_parser).parseTemplateLiteral(0xc00013a000, 0x1)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:469 +0x45
github.com/dop251/goja/parser.(*_parser).parseTaggedTemplateLiteral(0xc00013a000, {0x112b2a8, 0xc07d475180})
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:503 +0x2d
github.com/dop251/goja/parser.(*_parser).parseLeftHandSideExpressionAllowCall(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:665 +0xf4
github.com/dop251/goja/parser.(*_parser).parsePostfixExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:675 +0x25
github.com/dop251/goja/parser.(*_parser).parseUnaryExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:737 +0x2fe
github.com/dop251/goja/parser.(*_parser).parseMultiplicativeExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:742 +0x42
github.com/dop251/goja/parser.(*_parser).parseAdditiveExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:760 +0x42
github.com/dop251/goja/parser.(*_parser).parseShiftExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:777 +0x42
github.com/dop251/goja/parser.(*_parser).parseRelationalExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:795 +0x68
github.com/dop251/goja/parser.(*_parser).parseEqualityExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:839 +0x42
github.com/dop251/goja/parser.(*_parser).parseBitwiseAndExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:858 +0x42
github.com/dop251/goja/parser.(*_parser).parseBitwiseExclusiveOrExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:875 +0x42
github.com/dop251/goja/parser.(*_parser).parseBitwiseOrExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:892 +0x42
github.com/dop251/goja/parser.(*_parser).parseLogicalAndExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:909 +0x42
github.com/dop251/goja/parser.(*_parser).parseLogicalOrExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:926 +0x42
github.com/dop251/goja/parser.(*_parser).parseConditionalExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:942 +0x25
github.com/dop251/goja/parser.(*_parser).parseAssignmentExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:968 +0x12b
github.com/dop251/goja/parser.(*_parser).parseExpression(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/expression.go:1064 +0x62
github.com/dop251/goja/parser.(*_parser).parseStatement(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/statement.go:90 +0x2e9
github.com/dop251/goja/parser.(*_parser).parseSourceElements(...)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/statement.go:644
github.com/dop251/goja/parser.(*_parser).parseProgram(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/statement.go:654 +0x10e
github.com/dop251/goja/parser.(*_parser).parse(0xc00013a000)
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/parser.go:216 +0x85
github.com/dop251/goja/parser.ParseFile(0x0, {0x0, 0x1005359}, {0x10e5820, 0x11285d0}, 0x0, {0x0, 0x0, 0x0})
	/Users/matt/go/pkg/mod/github.com/dop251/goja@v0.0.0-20211207134806-acd374ca9c94/parser/parser.go:182 +0x252
main.main()
	/Users/matt/code/scratch/main.go:6 +0x39