Merge #429

429: Reorganize hir public API in terms of code model r=matklad a=matklad

Recently, I've been thinking about introducing "object orient code model" API for rust: a set of APIs with types like `Function`, `Module`, etc, with methods like `get_containing_declaration()`, `get_type()`, etc. 

Here's how a similar API might look like in .Net land:

https://docs.microsoft.com/en-us/dotnet/api/microsoft.codeanalysis.semanticmodel?view=roslyn-dotnet

https://docs.microsoft.com/en-us/dotnet/api/microsoft.codeanalysis.imethodsymbol?view=roslyn-dotnet

The main feature of such API is that it can be powered by different backends. For example, one can imagine a backend based on salsa, and a backend which reads all the data from a specially prepared JSON file. The "OO" bit is interesting mostly in this "can swap implementations via dynamic dispatch" aspect, the actual API could have a more database/ECS flavored feeling.

It's not clear at this moment how exactly should we implement such a dynamically (or if we even need dynamism in the first pace) swapable API in Rust, but I'd love to experiment with this a bit. 

For starters, I propose creating a `code_model_api` which contains various definition types and their public methods (mandatory implemented as one-liners, so that the API has a header-file feel). Specifically, I propose that each type is a wrapper around some integer ID, and that all methods of it accept a `&db` argument.  The actual impl goes elsewhere: into the db queries or, absent a better place, into the `code_model_api_impl`. In the first commit, I've moved the simplest type, `Crate`, over to this pattern.

I *think* that we, at least initially, will be used types from `code_model_api` *inside* `hir` as well, but this is not required: we might pick a different implementation down the line, while preserving the API. 

Long term I'd love to replace the `db: &impl HirDatabase` argument by a `mp: &dyn ModelProvider`, implement `ModelProvider` for `T: HirDatabase`, and move `code_model_api` into the separate crate, which does not depend on `hir`. 

@flodiebold you've recently done some `Def`s work, would do you think of this plan? Could it become a good API in the future, or is it just a useless boilerplate duplicating method signatures between `code_model_api` and `code_model_impl`?


Co-authored-by: Aleksey Kladov <[email protected]>

1 files changed, 4 insertions, 55 deletions

diff --git a/crates/ra_hir/src/query_definitions.rs b/crates/ra_hir/src/query_definitions.rs
index d9ee9d37f..f4b380022 100644
--- a/crates/ra_hir/src/query_definitions.rs
+++ b/crates/ra_hir/src/query_definitions.rs
@@ -6,20 +6,17 @@ use std::{
 use rustc_hash::FxHashMap;
 use ra_syntax::{
     AstNode, SyntaxNode,
-    ast::{self, NameOwner, ModuleItemOwner}
+    ast::{self, ModuleItemOwner}
 };
 use ra_db::{SourceRootId, Cancelable,};
 
 use crate::{
-    SourceFileItems, SourceItemId, DefKind, DefId, Name, AsName, HirFileId,
+    SourceFileItems, SourceItemId, DefKind, DefId, HirFileId,
     MacroCallLoc,
     db::HirDatabase,
     function::FnScopes,
-    module::{
-        ModuleSource, ModuleSourceNode, ModuleId,
-        imp::Submodule,
-        nameres::{InputModuleItems, ItemMap, Resolver},
-    },
+    module_tree::{ModuleId, ModuleSourceNode},
+    nameres::{InputModuleItems, ItemMap, Resolver},
     adt::{StructData, EnumData},
 };
 
@@ -61,54 +58,6 @@ pub(super) fn file_item(db: &impl HirDatabase, source_item_id: SourceItemId) ->
     }
 }
 
-pub(crate) fn submodules(
-    db: &impl HirDatabase,
-    source: ModuleSource,
-) -> Cancelable<Arc<Vec<Submodule>>> {
-    db.check_canceled()?;
-    let file_id = source.file_id();
-    let submodules = match source.resolve(db) {
-        ModuleSourceNode::SourceFile(it) => collect_submodules(db, file_id, it.borrowed()),
-        ModuleSourceNode::Module(it) => it
-            .borrowed()
-            .item_list()
-            .map(|it| collect_submodules(db, file_id, it))
-            .unwrap_or_else(Vec::new),
-    };
-    return Ok(Arc::new(submodules));
-
-    fn collect_submodules<'a>(
-        db: &impl HirDatabase,
-        file_id: HirFileId,
-        root: impl ast::ModuleItemOwner<'a>,
-    ) -> Vec<Submodule> {
-        modules(root)
-            .map(|(name, m)| {
-                if m.has_semi() {
-                    Submodule::Declaration(name)
-                } else {
-                    let src = ModuleSource::new_inline(db, file_id, m);
-                    Submodule::Definition(name, src)
-                }
-            })
-            .collect()
-    }
-}
-
-pub(crate) fn modules<'a>(
-    root: impl ast::ModuleItemOwner<'a>,
-) -> impl Iterator<Item = (Name, ast::Module<'a>)> {
-    root.items()
-        .filter_map(|item| match item {
-            ast::ModuleItem::Module(m) => Some(m),
-            _ => None,
-        })
-        .filter_map(|module| {
-            let name = module.name()?.as_name();
-            Some((name, module))
-        })
-}
-
 pub(super) fn input_module_items(
     db: &impl HirDatabase,
     source_root_id: SourceRootId,