Add the possibility to create a typeSymbol in the Quotes API

[hamzaremmal]

Closes #19448

[hamzaremmal]

Note that I didn't add a test for TypeBounds because calling tree.show will not print the bounds that were generated by TypeRepr.of[...]. Nevertheless, if we comment out the following two lines, the bounds will be printed too:

scala3/compiler/src/scala/quoted/runtime/impl/printers/SourceCode.scala

Line 1369 in 6af2bcf

case Inferred() =>

scala3/compiler/src/scala/quoted/runtime/impl/printers/SourceCode.scala

Line 1375 in 6af2bcf

case Inferred() => this

This is due to the fact that when a user writes the following code: type X >: Int, the compiler will infer the upper bound to Any. The following user written code (type X >: Int) will be represented as such in the Quotes API:

TypeDef(X,TypeBoundsTree(Ident(Int),TypeTree[TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Any)],EmptyTree))

The same type tree generated with the Quotes API will the represented as this:

TypeDef(X,TypeTree[TypeBounds(TypeRef(ThisType(TypeRef(NoPrefix,module class scala)),class Int),TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class <root>)),object scala),Any))])

Both representations are equivalent but due to how the printer is designed, we cannot show the bounds of the second representation at the moment

[smarter]

In the compiler, the info of a type symbol can either be a ClassInfo (if we're defining a class) or a TypeBounds (if we're defining a type parameter, a type alias, an abstract type member or an opaque type). So String is not a valid info, it should be TypeAlias(String), but giving the user higher-level methods like newTypeAlias and newTypeBounds would be better.

[jchyb]

We should also have a test of the use case from the original discussion:
Two macro methods: both a transparent inline and an inline macro method returning a trait with a bounded type member and a type alias type member, so the incorrect stuff we generate there can be caught by -Ycheck and -Xcheck-macros

[jchyb]

But great work so far! Especially with investigating the printer issue with the type bounds. I personally think showing the inferred stuff would be better than showing nothing, but this is something we can change in the future.

The TypeAlias issue makes me wonder whether the previous uses of TypeDef.apply were correct (I thought the only way to use it was to get the symbol from elsewhere and effectively use it as a type alias, but I don't think we wrap it with TypeAlias anywhere)

[jchyb]

Missing @experimental here and in def test I believe