move fuzzy source binding to a separete mode

crates/ra_hir/src/source_binder.rs

@@ -0,0 +1,94 @@
+/// Lookup hir elements using position in the source code. This is a lossy
+/// transformation: in general, a single source might correspond to several
+/// modules, functions, etc, due to macros, cfgs and `#[path=]` attributes on
+/// modules.
+///
+/// So, this modules should not be used during hir construction, it exists
+/// purely for "IDE needs".
+use ra_db::{FileId, FilePosition, Cancelable};
+use ra_editor::find_node_at_offset;
+use ra_syntax::{
+    ast::{self, AstNode},
+    SyntaxNodeRef,
+};
+
+use crate::{
+    HirDatabase, Module, Function, SourceItemId,
+    module::ModuleSource,
+    DefKind, DefLoc
+};
+
+/// Locates the module by `FileId`. Picks topmost module in the file.
+pub fn module_from_file_id(db: &impl HirDatabase, file_id: FileId) -> Cancelable<Option<Module>> {
+    let module_source = ModuleSource::new_file(db, file_id);
+    module_from_source(db, module_source)
+}
+
+/// Locates the module by position in the source code.
+pub fn module_from_position(
+    db: &impl HirDatabase,
+    position: FilePosition,
+) -> Cancelable<Option<Module>> {
+    let file = db.source_file(position.file_id);
+    let module_source = match find_node_at_offset::<ast::Module>(file.syntax(), position.offset) {
+        Some(m) if !m.has_semi() => ModuleSource::new_inline(db, position.file_id, m),
+        _ => ModuleSource::new_file(db, position.file_id),
+    };
+    module_from_source(db, module_source)
+}
+
+/// Locates the module by child syntax element within the module
+pub fn module_from_child_node(
+    db: &impl HirDatabase,
+    file_id: FileId,
+    child: SyntaxNodeRef,
+) -> Cancelable<Option<Module>> {
+    let module_source = if let Some(m) = child
+        .ancestors()
+        .filter_map(ast::Module::cast)
+        .find(|it| !it.has_semi())
+    {
+        ModuleSource::new_inline(db, file_id, m)
+    } else {
+        ModuleSource::new_file(db, file_id)
+    };
+    module_from_source(db, module_source)
+}
+
+fn module_from_source(
+    db: &impl HirDatabase,
+    module_source: ModuleSource,
+) -> Cancelable<Option<Module>> {
+    let source_root_id = db.file_source_root(module_source.file_id());
+    let module_tree = db.module_tree(source_root_id)?;
+
+    let module_id = ctry!(module_tree.any_module_for_source(module_source));
+    Ok(Some(Module::new(db, source_root_id, module_id)?))
+}
+
+pub fn function_from_source(
+    db: &impl HirDatabase,
+    file_id: FileId,
+    fn_def: ast::FnDef,
+) -> Cancelable<Option<Function>> {
+    let module = ctry!(module_from_child_node(db, file_id, fn_def.syntax())?);
+    let file_items = db.file_items(file_id);
+    let item_id = file_items.id_of(fn_def.syntax());
+    let source_item_id = SourceItemId { file_id, item_id };
+    let def_loc = DefLoc {
+        kind: DefKind::Function,
+        source_root_id: module.source_root_id,
+        module_id: module.module_id,
+        source_item_id,
+    };
+    Ok(Some(Function::new(def_loc.id(db))))
+}
+
+pub fn function_from_child_node(
+    db: &impl HirDatabase,
+    file_id: FileId,
+    node: SyntaxNodeRef,
+) -> Cancelable<Option<Function>> {
+    let fn_def = ctry!(node.ancestors().find_map(ast::FnDef::cast));
+    function_from_source(db, file_id, fn_def)
+}