[SymbolGraphGen] Automatically use new generics notation

[karwa]

Feature Name

Use new generics notation

Description

It would be nice if DocC had the ability to rewrite function signatures using the new generics notation. Package developers who need to support older versions of the compiler may need to keep using the angle-bracket notation, even in cases where it would be possible to use some types or primary associated types instead.

But for documentation, we still want to present the clearest interface to users, and both notations have equivalent meaning.
For example, if I write:

func foo<T: BinaryInteger>(_ value: T)

It would be nice if it appeared in documentation as:

func foo(_ value: some BinaryInteger)

Similarly, for primary associated types. I write:

func foo<Source: Collection>(_ value: Source) where Source.Element == UInt8

But that's long and wraps to multiple lines in the topics list. It's not very readable - type names ("Source") get introduced at the start, used in the middle, then explained using constraints at the end.

And it would be nice if DocC could present this as:

func foo(_ value: some Collection<UInt8>)

Even if I need to keep writing it the old way for compatibility purposes.

Motivation

No response

Importance

No response

Alternatives Considered

No response

[d-ronnqvist]

DocC itself isn't tied to any specific language so it wouldn't rewrite function signatures. Instead the symbol information that's displayed in DocC comes from the source language's compilers.

In order for DocC to display a Swift function defined like

func foo<Source: Collection>(_ value: Source) where Source.Element == UInt8

as some other format, for example

func foo(_ value: some Collection<UInt8>)

the Swift compiler would need to emit that declaration in the symbol graph file it passes to DocC. I'm not sure if that's a syntax transformation that possible to do on the AST.

[d-ronnqvist]

cc @QuietMisdreavus