Infix operation desugaring should preserve original span

[rochala]

Found during debugging of #22566

Basically, we created new apply based on arg inside Parens that led to shorter span.

        case Parens(arg) =>
          Apply(sel, assignToNamedArg(arg) :: Nil)

[som-snytt]

Sample diff of my suggestion that moves the point

--- a/tests/explicit-nulls/neg/byname-nullables1.check
+++ b/tests/explicit-nulls/neg/byname-nullables1.check.out
@@ -1,4 +1,4 @@
--- Error: tests/explicit-nulls/neg/byname-nullables1.scala:10:6 --------------------------------------------------------
+-- Error: tests/explicit-nulls/neg/byname-nullables1.scala:10:12 -------------------------------------------------------
 10 |    f(x.fld != null) // error
    |      ^^^^^^^^^^^^^
    |      This argument was typed using flow assumptions about mutable variables

showing point (column of the error pos) is the op of the infix op, not start of left operand.

[som-snytt]

I'll look at the other pos diffs from my suggestion, to check if they also make sense.

I agree with the logic of the original change here, but can't explain why "composition of positions" is so hard. I understand my suggested change without thinking much.

[Gedochao]

@rochala @som-snytt What's the status of this PR? is this still being worked on?

[som-snytt]

I rebased with a minor tweak. Probably will require an updated check file.

[rochala]

@som-snytt do you want to finish this or should I do it ?

[som-snytt]

@rochala I will keep pushing. "Learning by breaking." I will notify if I hit my perplexity budget. Thanks!

[rochala]

Thanks again, had similar idea but for me it was Claude :D

[som-snytt]

The CB c failure is mill, of course.

[94](https://github.com/scala/scala3/actions/runs/22076565460/job/63792831770?pr=22703#step:5:19095)
[127-1] - test.utest.AssertsTestsVersionSpecific 8ms
[127-1]   - assertCompileError 8ms
[127-1]     - failure 8ms
[127-1]       + 0 5ms  
[127-1]       + 1 0ms  
[127-1]       X 2 3ms 
[127-1]         java.lang.AssertionError: assertion failed: Compile error positions do not match
[127-1]         Expected Position
[127-1]         assertCompileError("1" * 2).check("")
[127-1]                            ^
[127-1]         Actual Position
[127-1]         assertCompileError("1" * 2).check("")
[127-1]                                ^
[127-1]           scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:10)
[127-1]           utest.CompileError.check(Errors.scala:184)
[127-1]           utest.CompileError.check$(Errors.scala:152)
[127-1]           utest.CompileError$Type.check(Errors.scala:204)
[127-1]           test.utest.AssertsTestsVersionSpecific$.tests$$anonfun$1$$anonfun$1$$anonfun$1$$anonfun$3(AssertsTestsVersionSpecific.scala:35)