Implement inlay hints

[resolritter]

Announcement: https://devblogs.microsoft.com/typescript/announcing-typescript-4-4-beta/#inlay-hints
Linked PR: microsoft/TypeScript#42089 (was already merged)

I believe this has not yet landed on a stable release although 4.4 is scheduled for next month already

[chemzqm]

It's not possible to add inline virtual text on both vim and neovim, so send your feature request to vim/neovim fist.

[resolritter]

It could work with virtual text at the end of the line in Neovim, like coc-rust-analyzer

[fannheyward]

I'll take a look on this after TS 4.4 released. There're several works:

1. tsserver makes its own inlayHint protocol implementation, but LSP is working on a new/standard protocol on Add proposed textDocument/inlayHints to protocol & client. microsoft/vscode-languageserver-node#772
2. display with virtual text, it works but not perfect, this needs vim/nvim more works

[fannheyward]

Test code:

// enumMemberValues
enum E1 {
  A,
  B,
}

enum E2 {
  A = 0,
  B = 1,
}

// functionLikeReturnTypes
function foo() {
  return Date.now()
}

function bar(): number {
  return Date.now()
}

// parameterNames
parseInt('123', 8)

// parameterTypes
document.addEventListener('click', e => {
  console.log(e)
})

// propertyDeclarationTypes
class Bar {
  prop = Date.now;
}

// variableTypes
const xxf = Date.now()

In VSCode:

In coc, only enumMemberValues, functionLikeReturnTypes and variableTypes are enabled.

Because we can't set inline virtual text, parameterNames, parameterTypes and propertyDeclarationTypes are disabled.

@chemzqm any thoughts on this? Do we need to add this in coc-tsserver?

[fannheyward]

The variableTypes hints should be disabled too.

[hadnet]

How is this going, guys? Any updates? When can we use this feature?