Refine the type of inline vals with literal rhs

[mbovel]

Closes #24321.

This PR changes the type of inline vals to be the exact type of the right-hand side if it is a literal, such that in following snippet, x would have type (4: Int):

inline val x: Int = 4

> scalac -Xprint:typer test.scala
...
[[syntax trees at end of                     typer]] // test.scala
...
    inline val x: (4 : Int) = 4
...

Previously, it would not compile:

$ scala -S 3.7.3 test.scala
Compiling project (Scala 3.7.3, JVM (17))
[error] ./test.scala:1:15
[error] inline value must have a literal constant type
[error] inline val x: Int = 4
[error]               ^^^
Error compiling project (Scala 3.7.3, JVM (17))
Compilation failed

[mbovel]

@sjrd do you think that would require a SIP?

[hamzaremmal]

@sjrd do you think that would require a SIP?

At least a minor release.

[sjrd]

It definitely needs a minor release.

In theory this is SIP material ... but IMO the SIP process is way too heavy for this. Let's add it to the next agenda, and hopefully there will be quick consensus.

[hamzaremmal]

Couldn't we have just reused the tracked system?

Nevermind, but I think it's worth checking the interactions between the two.

[mbovel]

I think it's worth checking the interactions between the two.

I added a test that checks that: https://github.com/dotty-staging/dotty/blob/345fcba592e8e9e276fc0cbcd4396682cb8739e7/tests/neg/inline-tracked-val.scala ✅