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This looks like a great alternative to TypeScript + Node.js which I currently use. My main gripe with Lua (and thus Luau) is colons. It's so easy to forget the

This looks like a great alternative to TypeScript + Node.js which I currently use. My main gripe with Lua (and thus Luau) is colons. It's so easy to forget them. Does the type checker catch this error? And if so, does it catch it every time, provided you always use types? If so, that could be good enough for me. Especially if it has strong LSP + VS Code support.

gsck 1y ago
Do you mean colons for calling methods of an object, or semicolons at the end of lines?
- LoganDark 1y ago
  Lua doesn't require semicolons at the end of lines. (Or lines at all.) Meanwhile accidentally using a period instead of a colon (field call instead of namecall) is completely semantically different (namecall passes self).
Moomoomoo309 1y ago
Oh, Lua's type checker doesn't check function calls at all. Pass too few arguments? The rest are nil. Pass too many? The extras are dropped. An editor could check for it relatively easily (and some do, I think), but the language doesn't care at all.
- debugnik 1y ago
  Is this true of Luau as well, which is the dialect used here? Or are you talking about just Lua (which doesn't have a type checker at all) or LuaLS? I'd check for myself but Luau's web demo seems to lack the most important feature of their dialect, type checking.
  - parenwielder 1y ago
    Hi there, I’m from the Luau team. Just wanted to clarify that no, nothing they said about the type system is true of Luau. It reads like a comment about Lua’s runtime typechecking maybe (which is as limited as you’d expect from a dynamically typed language).
    - debugnik 1y ago
      Thanks, I suspected as much! Since you're here: Is it reasonably feasible for users to add declaration files for code exported from the host application? The lack of documentation got me stuck the last time I tried to embed Luau. Aside from that, I'm very excited about it!
      - deviaze 1y ago
        Yes! As an embedder you can write definition and declaration files! Declaration files are usually named like `globals.d.luau` and have a slightly different syntax than regular Luau. But it's really easy to set up global def files that you can pass to luau-lsp. Atm for my Luau runtime (seal), I have a small globals.d.luau and just bundle all the stdlib type files in a typedefs folder that gets included alongside my binary: https://github.com/deviaze/seal/tree/main/.seal https://github.com/deviaze/seal/tree/main/.seal This is just because definition files don't support doc comments yet (for hovers w/ luau-lsp)
- SkiFire13 1y ago
  > Lua's type checker Lua has a type checker?
parenwielder 1y ago
Luau’s type system does arity checking and type checking for function calls, and even has a specialized error that detects when you probably meant to write a colon instead of a dot.
CompeyDev 1y ago
Luau is gradually typed, so as long as you type it strictly (which is a little bit more than just defining the method with colon-notation, but there has been interest in making it simpler), it will catch this. Unless you're using metatables, this would just be manually defining `self` with a type containing the fields you want it to represent. For example: ```luau local Module = {} export type Module = { field: string } function Module.Something(self: Module) print(self.field) end return Module ``` EDIT: oops, new to this site; expected codeblocks to be a thing :p

gsck 1y ago

Do you mean colons for calling methods of an object, or semicolons at the end of lines?

LoganDark 1y ago
Lua doesn't require semicolons at the end of lines. (Or lines at all.) Meanwhile accidentally using a period instead of a colon (field call instead of namecall) is completely semantically different (namecall passes self).

Moomoomoo309 1y ago

Oh, Lua's type checker doesn't check function calls at all. Pass too few arguments? The rest are nil. Pass too many? The extras are dropped. An editor could check for it relatively easily (and some do, I think), but the language doesn't care at all.

debugnik 1y ago
Is this true of Luau as well, which is the dialect used here? Or are you talking about just Lua (which doesn't have a type checker at all) or LuaLS? I'd check for myself but Luau's web demo seems to lack the most important feature of their dialect, type checking.
- parenwielder 1y ago
  Hi there, I’m from the Luau team. Just wanted to clarify that no, nothing they said about the type system is true of Luau. It reads like a comment about Lua’s runtime typechecking maybe (which is as limited as you’d expect from a dynamically typed language).
  - debugnik 1y ago
    Thanks, I suspected as much! Since you're here: Is it reasonably feasible for users to add declaration files for code exported from the host application? The lack of documentation got me stuck the last time I tried to embed Luau. Aside from that, I'm very excited about it!
    - deviaze 1y ago
      Yes! As an embedder you can write definition and declaration files! Declaration files are usually named like `globals.d.luau` and have a slightly different syntax than regular Luau. But it's really easy to set up global def files that you can pass to luau-lsp. Atm for my Luau runtime (seal), I have a small globals.d.luau and just bundle all the stdlib type files in a typedefs folder that gets included alongside my binary: https://github.com/deviaze/seal/tree/main/.seal https://github.com/deviaze/seal/tree/main/.seal This is just because definition files don't support doc comments yet (for hovers w/ luau-lsp)
SkiFire13 1y ago
> Lua's type checker Lua has a type checker?

parenwielder 1y ago

Luau’s type system does arity checking and type checking for function calls, and even has a specialized error that detects when you probably meant to write a colon instead of a dot.

CompeyDev 1y ago

Luau is gradually typed, so as long as you type it strictly (which is a little bit more than just defining the method with colon-notation, but there has been interest in making it simpler), it will catch this. Unless you're using metatables, this would just be manually defining `self` with a type containing the fields you want it to represent. For example: ```luau local Module = {} export type Module = { field: string } function Module.Something(self: Module) print(self.field) end return Module ``` EDIT: oops, new to this site; expected codeblocks to be a thing :p