complete_import: add new import resolver infrastructure with some hardcoded importable name.

Changes complete_scope to support that.

crates/ra_hir/src/resolve.rs

@@ -3,6 +3,8 @@ use std::sync::Arc;
 
 use rustc_hash::FxHashMap;
 
+use ra_syntax::SmolStr;
+
 use crate::{
     ModuleDef,
     code_model_api::Crate,
@@ -12,8 +14,12 @@ use crate::{
     generics::GenericParams,
     expr::{scope::{ExprScopes, ScopeId}, PatId},
     impl_block::ImplBlock,
+<<<<<<< HEAD
     path::Path,
     Trait
+=======
+    path::Path, Trait,
+>>>>>>> complete_import: add new import resolver infrastructure with some hardcoded importable name.
 };
 
 #[derive(Debug, Clone, Default)]
@@ -21,6 +27,12 @@ pub(crate) struct Resolver {
     scopes: Vec<Scope>,
 }
 
+#[derive(Debug, Clone, Default)]
+pub(crate) struct ImportResolver {
+    // todo: use fst crate or something like that
+    dummy_names: Vec<(SmolStr, Vec<SmolStr>)>,
+}
+
 // FIXME how to store these best
 #[derive(Debug, Clone)]
 pub(crate) struct ModuleItemMap {
@@ -309,3 +321,56 @@ impl Scope {
         }
     }
 }
+
+impl ImportResolver {
+    pub(crate) fn new() -> Self {
+        let dummy_names = vec![
+            (SmolStr::new("fmt"), vec![SmolStr::new("std"), SmolStr::new("fmt")]),
+            (SmolStr::new("io"), vec![SmolStr::new("std"), SmolStr::new("io")]),
+            (SmolStr::new("iter"), vec![SmolStr::new("std"), SmolStr::new("iter")]),
+            (SmolStr::new("hash"), vec![SmolStr::new("std"), SmolStr::new("hash")]),
+            (
+                SmolStr::new("Debug"),
+                vec![SmolStr::new("std"), SmolStr::new("fmt"), SmolStr::new("Debug")],
+            ),
+            (
+                SmolStr::new("Display"),
+                vec![SmolStr::new("std"), SmolStr::new("fmt"), SmolStr::new("Display")],
+            ),
+            (
+                SmolStr::new("Hash"),
+                vec![SmolStr::new("std"), SmolStr::new("hash"), SmolStr::new("Hash")],
+            ),
+            (
+                SmolStr::new("Hasher"),
+                vec![SmolStr::new("std"), SmolStr::new("hash"), SmolStr::new("Hasher")],
+            ),
+            (
+                SmolStr::new("Iterator"),
+                vec![SmolStr::new("std"), SmolStr::new("iter"), SmolStr::new("Iterator")],
+            ),
+        ];
+
+        ImportResolver { dummy_names }
+    }
+
+    // Returns a map of importable items filtered by name.
+    // The map associates item name with its full path.
+    // todo: should return Resolutions
+    pub(crate) fn all_names(
+        &self,
+        _db: &impl HirDatabase,
+        name: &Name,
+    ) -> FxHashMap<SmolStr, Vec<SmolStr>> {
+        let name = name.to_smolstr();
+        if name.len() > 1 {
+            self.dummy_names
+                .iter()
+                .filter(|(n, _)| n.as_str().contains(name.as_str()))
+                .cloned()
+                .collect()
+        } else {
+            FxHashMap::default()
+        }
+    }
+}