code of "`" should throw unterminated template literal error

[jdalton]

At the moment code of a single tick ` throws an unexpected token error but it should be an unterminated template literal error.

It errors at the this.expect(tt.dollarBraceL) check at

acorn/src/expression.js

Lines 527 to 534 in a2f254a

	pp.parseTemplate = function({isTagged = false} = {}) {
	let node = this.startNode()
	this.next()
	node.expressions = []
	let curElt = this.parseTemplateElement({isTagged})
	node.quasis = [curElt]
	while (!curElt.tail) {
	this.expect(tt.dollarBraceL)

It could be handled in parseTemplateElement() with a check before setting the .tail to throw the appropriate error or somewhere in readTmplToken.

[jdalton]

Thanks @marijnh!