Regression in 5.1.1 related to template literals

[shnhrrsn]

I'm seeing an issue in 5.1.1 that’s not present prior (tested 5.0.3 and 5.1.0).

Here’s my how I’m testing:

sample.js:

console.log(`${JSON.stringify({
	class: 'testing'
})}`)

test.js:

const acorn = require('acorn')
const fs = require('fs')
const sample = fs.readFileSync('./sample.js').toString()
acorn.parse(sample)

Running this in both Node 8.2 and through acorn.parse in 5.0.3 and 5.1.0 works fine. Trying to parse it in 5.1.1 yields the following:

node acorn.js       
./node_modules/acorn/dist/acorn.js:3457
      throw err
      ^

SyntaxError: Unterminated template (3:4)
    at Parser.pp$4.raise (./node_modules/acorn/dist/acorn.js:2610:13)
    at Parser.pp$8.readTmplToken (./node_modules/acorn/dist/acorn.js:3477:53)
    at Parser.pp$8.tryReadTemplateToken (./node_modules/acorn/dist/acorn.js:3452:10)
    at TokContext.types$1.q_tmpl [as override] (./node_modules/acorn/dist/acorn.js:2764:67)
    at Parser.pp$8.nextToken (./node_modules/acorn/dist/acorn.js:2965:48)
    at Parser.pp$8.next (./node_modules/acorn/dist/acorn.js:2923:8)
    at Parser.pp$3.parseTemplateElement (./node_modules/acorn/dist/acorn.js:2235:8)
    at Parser.pp$3.parseTemplate (./node_modules/acorn/dist/acorn.js:2254:38)
    at Parser.pp$3.parseExprAtom (./node_modules/acorn/dist/acorn.js:2091:17)
    at Parser.pp$3.parseExprSubscripts (./node_modules/acorn/dist/acorn.js:1955:19)

It appears to be the class key, if I quote it it works fine. Interestingly, if I keep the same JSON.stringify block of code without template literals, acorn parses it just fine.

[mysticatea]

I have the same issue.

Repro steps

1. Execute the following code with acorn@latest (5.1.1)

const acorn = require("acorn")
const code = `
    \`\${ foo({class: 1}) }\`
`

console.log(acorn.version)
console.log(code)
console.log(acorn.parse(code, {ecmaVersion: 8}))

Expected result

※ This is the result of acorn@5.0.3.

5.0.3

    `${ foo({class: 1}) }`

Node {
  type: 'Program',
  start: 0,
  end: 28,
  body:
   [ Node {
       type: 'ExpressionStatement',
       start: 5,
       end: 27,
       expression: [Object] } ],
  sourceType: 'script' }

Actual result

※ This is the result of acorn@5.1.1.

5.1.1

    `${ foo({class: 1}) }`

C:\Users\t-nagashima.MSS\dev\sandbox\node_modules\acorn\dist\acorn.js:3457
      throw err
      ^

SyntaxError: Unterminated template (2:26)
    at Parser.pp$4.raise (C:\Users\t-nagashima.MSS\dev\sandbox\node_modules\acorn\dist\acorn.js:2610:13)
    at Parser.pp$8.readTmplToken (C:\Users\t-nagashima.MSS\dev\sandbox\node_modules\acorn\dist\acorn.js:3477:53)
    at Parser.pp$8.tryReadTemplateToken (C:\Users\t-nagashima.MSS\dev\sandbox\node_modules\acorn\dist\acorn.js:3452:10)
    at TokContext.types$1.q_tmpl [as override] (C:\Users\t-nagashima.MSS\dev\sandbox\node_modules\acorn\dist\acorn.js:2764:67)
    at Parser.pp$8.nextToken (C:\Users\t-nagashima.MSS\dev\sandbox\node_modules\acorn\dist\acorn.js:2965:48)
    at Parser.pp$8.next (C:\Users\t-nagashima.MSS\dev\sandbox\node_modules\acorn\dist\acorn.js:2923:8)
    at Parser.pp$3.parseTemplateElement (C:\Users\t-nagashima.MSS\dev\sandbox\node_modules\acorn\dist\acorn.js:2235:8)
    at Parser.pp$3.parseTemplate (C:\Users\t-nagashima.MSS\dev\sandbox\node_modules\acorn\dist\acorn.js:2254:38)
    at Parser.pp$3.parseExprAtom (C:\Users\t-nagashima.MSS\dev\sandbox\node_modules\acorn\dist\acorn.js:2091:17)
    at Parser.pp$3.parseExprSubscripts (C:\Users\t-nagashima.MSS\d