Associated items support

[lnicola]

struct Foo;

impl Foo {
    const BAR: i32 = 42;
}

fn main() {
    let x = Foo::BAR;
}

Foo::BAR does not get resolved.

[DJMcNab]

Neither do associated functions (or types, if they can exist without a trait)

[matklad]

Given that we already can detect inherent impls, this shouldn't be too hard to add.

The relevant completion code is here:

https://github.com/rust-analyzer/rust-analyzer/blob/db6d214411505de6534fce183e9bea8109bc5283/crates/ra_ide_api/src/completion/complete_path.rs#L9

impls_in_crate query could be used to get the set of the impls. Using this set, one can find impls for a particular type:

https://github.com/rust-analyzer/rust-analyzer/blob/db6d214411505de6534fce183e9bea8109bc5283/crates/ra_hir/src/ty/method_resolution.rs#L43-L56

To get the ty to find the impls, we should resolve path prefix (Foo) to a Def and then use a type_for_def query. Note that this is slightly inaccurate, because it won't take possible substitutions into account, but this should be OK for completion.

[lnicola]

I tried to look into it, but for some reason I have trouble building the code after making any changes. It did work after I added the first log calls, but now it doesn't compile any more.

$ cargo install-code
[snip]
$ git stash pop
On branch master
Your branch is up to date with 'origin/master'.

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

	modified:   complete_path.rs

no changes added to commit (use "git add" and/or "git commit -a")
Dropped refs/stash@{0} (0d39549b2709395fc5569444efdb9ab2b919202c)
$ cargo install-code # why is it rebuilding the tools?
   Compiling num-traits v0.2.6
   Compiling serde v1.0.87
   Compiling spin v0.4.10
   Compiling syn v0.15.26
   Compiling lazy_static v1.2.0
   Compiling thread_local v0.3.6
   Compiling regex v1.1.0
   Compiling num-integer v0.1.39
   Compiling serde_derive v1.0.87
   Compiling pest_generator v2.1.0
   Compiling synstructure v0.10.1
   Compiling pest_derive v2.1.0
   Compiling failure_derive v0.1.5
   Compiling failure v0.1.5
   Compiling chrono v0.4.6
   Compiling serde_json v1.0.38
   Compiling ron v0.4.1
   Compiling tera v0.11.20
   Compiling teraron v0.0.1
   Compiling tools v0.1.0 (/home/grayshade/rust-analyzer/crates/tools)
    Finished dev [unoptimized + debuginfo] target(s) in 32.41s
     Running `/home/grayshade/rust-analyzer/target/debug/tools install-code`

will run: cargo install --path crates/ra_lsp_server --force
  Installing ra_lsp_server v0.1.0 (/home/grayshade/rust-analyzer/crates/ra_lsp_server)
   Compiling ra_ide_api v0.1.0 (/home/grayshade/rust-analyzer/crates/ra_ide_api)
error[E0599]: no method named `parse` found for type `&db::RootDatabase` in the current scope
  --> crates/ra_ide_api/src/completion.rs:49:28
   |
49 |     let original_file = db.parse(position.file_id);
   |                            ^^^^^
   |
   = note: the method `parse` exists but the following trait bounds were not satisfied:
           `&db::RootDatabase : ra_db::SourceDatabase`
           `db::RootDatabase : ra_db::SourceDatabase`
   = help: items from traits can only be used if the trait is implemented and in scope
   = note: the following trait defines an item `parse`, perhaps you need to implement it:
           candidate #1: `ra_db::SourceDatabase`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0599`.
error: failed to compile `ra_lsp_server v0.1.0 (/home/grayshade/rust-analyzer/crates/ra_lsp_server)`, intermediate artifacts can be found at `/home/grayshade/rust-analyzer/target`

Caused by:
  Could not compile `ra_ide_api`.

To learn more, run the command again with --verbose.
Error: ErrorMessage { msg: "`cargo install --path crates/ra_lsp_server --force` exited with exit code: 101" }
$ git status
On branch master
Your branch is up to date with 'origin/master'.

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

	modified:   complete_path.rs

no changes added to commit (use "git add" and/or "git commit -a")
$ git diff                 
diff --git i/crates/ra_ide_api/src/completion/complete_path.rs w/crates/ra_ide_api/src/completion/complete_path.rs
index 39aefdb1..e05b4eff 100644
--- i/crates/ra_ide_api/src/completion/complete_path.rs
+++ w/crates/ra_ide_api/src/completion/complete_path.rs
@@ -7,14 +7,17 @@ use crate::{
 };
 
 pub(super) fn complete_path(acc: &mut Completions, ctx: &CompletionContext) {
+    log::info!("complete_path");
     let path = match &ctx.path_prefix {
         Some(path) => path.clone(),
         _ => return,
     };
+    log::info!("{:?}", path);
     let def = match ctx.resolver.resolve_path(ctx.db, &path).take_types() {
         Some(Resolution::Def(def)) => def,
         _ => return,
     };
+    log::info!("{:?}", def);
     match def {
         hir::ModuleDef::Module(module) => {
             let module_scope = module.scope(ctx.db);
@@ -48,6 +51,10 @@ pub(super) fn complete_path(acc: &mut Completions, ctx: &CompletionContext) {
                 }
             });
         }
+        // hir::ModuleDef::Struct(s) => {
+        //     let ty = s.ty(ctx.db);
+        //     log::info!("{:?}", ty);
+        // }
         _ => return,
     };
 }

Notice that I haven't touched the file it complains about.

[lnicola]

Ah, rust-lang/rust#58291.

[lnicola]

Filed #801.