Illegal quote/splice syntax passing through parser

[nicolasstucki]

Compiler version

3.1.1

Minimized code

import scala.quoted.*

def q1(using Quotes): Expr[Int] = '{ 1 }
def q2(using Quotes): Expr[Int] = ' { 1 } // compiles but should not
def q3(using Quotes): Expr[Int] = '{ ${ foo } }
def q4(using Quotes): Expr[Int] = '{ $ { foo } } // compiles but should not

Expectation

They should have the same syntactic rules as string interpolators. ' or $ must be immediately followed by a {.

For examples the equivalent string interpolators

def s1 = s"abc"

def s2 = s "abc" // does not compile

def s3 = s"<${"abc"}>"

def s4 = s"<$ {"abc"}>" // does not compile

Also see

• https://github.com/lampepfl/dotty/blob/master/compiler/src/dotty/tools/dotc/parsing/Parsers.scala#L2247-L2248
• https://github.com/lampepfl/dotty/blob/master/compiler/src/dotty/tools/dotc/parsing/Parsers.scala#L2232
• https://github.com/lampepfl/dotty/blob/master/compiler/src/dotty/tools/dotc/parsing/Parsers.scala#L1569-L1570

[tgodzik]

If this gets removed we should also revert https://github.com/scalameta/scalameta/pull/2487/files

[nicolasstucki]

Even stranger

import scala.quoted.*

def q2(using Quotes): Expr[Int] = ' /*aa*/ {
  println("hello")
  $/*a*/{ println(2); ' /*a*/ {3} }

}

[odersky]

That's not what the rules say. string interpolators are different since we are in a string where whitespace counts. For quotes and splices, they are technically a two token sequences.