@annotation.nowarn ignored/lost during inlining

[MartinHH]

Compiler version

3.6.3, 3.3.5 (and many others)

Minimized code

A minimal library (use scala publish local <first_filename> to publish it locally):

//> using scala "3.6.3"

//> using option "-Xfatal-warnings"

//> using publish.organization "io.bar.foo"
//> using publish.name "deprecation-bug-example"
//> using publish.version "0.0.1"

package io.bar.foo.example

@annotation.nowarn("cat=deprecation")
inline def dooFoo: String =
  val stream = Stream.empty
  stream.toString

Then a usage of that library:

//> using scala "3.6.3"

//> using dep "io.bar.foo::deprecation-bug-example::0.0.1"

val x = io.bar.foo.example.dooFoo

Use scala compile <second_filename> to compile it

Output

Compiling project (Scala 3.6.3, JVM (23))
Warning: there was 1 deprecation warning; re-run with -deprecation for details
Compiled project (Scala 3.6.3, JVM (23))

Expectation

No deprecation warning is emitted (as it is the case if dooFoo is not declared inline).

[som-snytt]

There are a few issues.

Taking a step back, it's not obvious that the expectation is correct. @nowarn is for "local warning suppression".

Inlining checks the "call site", so that inlining a deprecated method will warn.

CrossVersionChecks checks the expansion; the diagnostic is issued at the inlined position, which under separate compilation is not a current source. It would be more natural to see the warning at the non-inlined position, with an explanation that inlined code was involved. This may depend on a hypothetical option that selects how warnings and lints are applied to expanded code.

Apparently, it currently does not respect:

//> using option "-Werror"

Please note the correct spelling of the option to turn warnings into errors without using -Wconf:any:e.

$ scala-cli compile --server=false -S 3.6.3 -d ~/sandbox -cp ~/sandbox tests/warn/i22672/usage_2.scala
-- Deprecation Warning: lib_1.scala:11:2 ---------------------------------------
11 |  g
   |  ^
   |  method g in package p is deprecated since 1.0: old api
1 warning found

after adding a noninlined deprecation, it works (fails the compilation)

-- Deprecation Warning: /home/amarki/projects/dotty/tests/warn/i22672/usage_2.scala:11:14
11 |def failing = huh
   |              ^^^
   |method huh in package q is deprecated since 0.1: do I even know how it works
No warnings can be incurred under -Werror (or -Xfatal-warnings)
-- Deprecation Warning: lib_1.scala:11:2 ---------------------------------------
11 |  g
   |  ^
   |  method g in package p is deprecated since 1.0: old api
2 warnings found
1 error found
Compilation failed

To satisfy the expectation, inlining should inline the symbol's @nowarn at the inlined body. That sounds reasonable and doable.

But currently, annotating the inlined expression doesn't work (the annotations are collected in typer on a per-file basis).

-- Deprecation Warning: lib_1.scala:11:2 ---------------------------------------
11 |  g: @nowarn
   |  ^
   |  method g in package p is deprecated since 1.0: old api

I haven't checked yet if transparent inline conforms to expectations. (Edit: It correctly warns posttyper.)

[som-snytt]

The PR uses any annotation it finds on the inline method or its body to "register" the suppression.

All positions are in terms of the inlined source.