Define: Go to definition, declaration, implementation, type definition

[kjeremy]

The LSP (as of 3.15) supports go to definition, declaration, implementation and type definition.

What do these mean in a rust world? Does supporting all of the above features make sense? We should define what each of the above operations mean and figure out what makes sense for rust.

Context: #2538 (comment)

[flodiebold]

Thinking out loud...

For a file module:

• definition goes to the file
• declaration goes to the mod foo;
• implementation N/A or same as definition?
• type definition N/A

For a variable, const or static:

• definition goes to the let/const/static foo
• declaration same
• implementation N/A
• type definition goes to the ... definition of the type

For a trait method (call or implementation):

• declaration goes to the fn foo in the trait
• definition same? or same as implementation?
• implementation goes to the fn foo in the impl if we know it
• type definition N/A

For an inherent method (call):

• definition/declaration/implementation go to the fn foo in the impl
• type definition N/A

[matklad]

definition same? or same as implementation?

Same as implementation. You can unambigiously go from that to declaration, but not in the opposite direction.

IntelliJ Rust recently implemented a crazily neat feature where, when to you go to def for a method, it remembers the substitution, and subsequent goto defs take these substitutions into account.

Ie, goto def 92.to_string() brings you to blanket impl of ToString for display, and second goto there brings you to imp Display for i32 ⚡ ⚡ ⚡

[tigregalis]

I'm using VS Code. I'm not sure if this is the right issue to ask. I expected go to definition (F12) to go to the fn foo in the impl, but it goes to the fn foo in the trait. And go to implementation (Ctrl+F12) goes nowhere. I don't see go to declaration.

For a trait method (call or implementation):

• declaration goes to the fn foo in the trait

• definition same? or same as implementation?

• implementation goes to the fn foo in the impl if we know it

• type definition N/A

[flodiebold]

We don't have a way to find the trait implementation yet. There's e.g. #4558 for this, and it's mostly why this issue is still open as well.