Merge back #21799

[hamzaremmal]

#21799 was reverted as it broke main. See #21895 for more details.

The following error was reported on multiple merge commits to main

 Wrong number of warnings encountered when compiling tests\warn\i21860.scala
expected: 0, actual: 1

Unexpected warnings:
tests\warn\i21860.scala:11
-> following the diagnostics:
 at 11: Unreachable case
Error:  Test dotty.tools.dotc.CompilationTests.warn failed: java.lang.AssertionError: Warn test failed, but should not, reasons:
Error:  encountered 1 test failure(s):
Error:    - generic failure (see test output), took 18.087 sec
Error:      at dotty.tools.vulpix.ParallelTesting$CompilationTest.checkPass(ParallelTesting.scala:1257)
Error:      at dotty.tools.vulpix.ParallelTesting$CompilationTest.checkWarnings(ParallelTesting.scala:1176)
Error:      at dotty.tools.dotc.CompilationTests.warn(CompilationTests.scala:132)
Error:      ...