@som-snytt I'll assign you for now, let me know if you'll have the time for this

I'll take a look. It's a little strange to rewrite a bug.

Edit: I see it's analogous to the existing new warning, but for the zero-arg case.

Implicit parameters should be provided with a `using` clause.

Just noticed that you don't get rewrites on errors (I knew that). Since this is "just a bug" and not a syntax migration "per se", maybe it should just supply an extra-helpful message.

I forgot to check that the bug was introduced at some point (maybe in the change I reverted):

➜  dotty git:(issue/22792-rewrite-bad-parens) ✗ scala-cli compile --server=false -S 3.3.3 tests/rewrites/i22792.scala
Downloading Scala 3.3.3 compiler
-- [E171] Type Error: /home/amarki/projects/dotty/tests/rewrites/i22792.scala:8:30
8 |@main def Test = new Foo().run()
  |                 ^^^^^^^^^^^^^^^
  |missing argument for parameter ev of method run in class Foo: (implicit ev: Permit): Unit
1 error found
Compilation failed
➜  dotty git:(issue/22792-rewrite-bad-parens) ✗ scala-cli compile --server=false -S 3.3.4 tests/rewrites/i22792.scala
Downloading Scala 3.3.4 compiler
➜  dotty git:(issue/22792-rewrite-bad-parens) ✗

Probably backported to LTS in 3.3.4? (Edit: from 3.4.2. 2024 was quite a busy year. I remember I restored code from early in the year; 3.4.2 was May; 3.3.4 was Sept, I'm not sure it inherited all the changes.)

For the record, I see how to emit the patch when failing the application -- there is no position to use when the error is emitted, as there are no args...

Edit: that is, at the one-liner that caused the regression last year, there is no position to emit a warning with a patch; failing allows checking the diagnostics up the stack, mapping it to a warning, and restarting the adapt to no args (i.e. effectively dropping the spurious parens). (Keeping the 3.6 behavior as "bug-compatible" seems dubious to me, but I'll think about it more.)