style: rename crates to kebab case

crates/hir-ty/src/autoderef.rs

@@ -0,0 +1,142 @@
+//! In certain situations, rust automatically inserts derefs as necessary: for
+//! example, field accesses `foo.bar` still work when `foo` is actually a
+//! reference to a type with the field `bar`. This is an approximation of the
+//! logic in rustc (which lives in librustc_typeck/check/autoderef.rs).
+
+use std::sync::Arc;
+
+use chalk_ir::cast::Cast;
+use hir_expand::name::name;
+use limit::Limit;
+use syntax::SmolStr;
+
+use crate::{
+    db::HirDatabase, infer::unify::InferenceTable, Canonical, Goal, Interner, ProjectionTyExt,
+    TraitEnvironment, Ty, TyBuilder, TyKind,
+};
+
+static AUTODEREF_RECURSION_LIMIT: Limit = Limit::new(10);
+
+pub(crate) enum AutoderefKind {
+    Builtin,
+    Overloaded,
+}
+
+pub(crate) struct Autoderef<'a, 'db> {
+    pub(crate) table: &'a mut InferenceTable<'db>,
+    ty: Ty,
+    at_start: bool,
+    steps: Vec<(AutoderefKind, Ty)>,
+}
+
+impl<'a, 'db> Autoderef<'a, 'db> {
+    pub(crate) fn new(table: &'a mut InferenceTable<'db>, ty: Ty) -> Self {
+        let ty = table.resolve_ty_shallow(&ty);
+        Autoderef { table, ty, at_start: true, steps: Vec::new() }
+    }
+
+    pub(crate) fn step_count(&self) -> usize {
+        self.steps.len()
+    }
+
+    pub(crate) fn steps(&self) -> &[(AutoderefKind, Ty)] {
+        &self.steps
+    }
+
+    pub(crate) fn final_ty(&self) -> Ty {
+        self.ty.clone()
+    }
+}
+
+impl Iterator for Autoderef<'_, '_> {
+    type Item = (Ty, usize);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.at_start {
+            self.at_start = false;
+            return Some((self.ty.clone(), 0));
+        }
+
+        if AUTODEREF_RECURSION_LIMIT.check(self.steps.len() + 1).is_err() {
+            return None;
+        }
+
+        let (kind, new_ty) = autoderef_step(self.table, self.ty.clone())?;
+
+        self.steps.push((kind, self.ty.clone()));
+        self.ty = new_ty;
+
+        Some((self.ty.clone(), self.step_count()))
+    }
+}
+
+pub(crate) fn autoderef_step(table: &mut InferenceTable, ty: Ty) -> Option<(AutoderefKind, Ty)> {
+    if let Some(derefed) = builtin_deref(&ty) {
+        Some((AutoderefKind::Builtin, table.resolve_ty_shallow(derefed)))
+    } else {
+        Some((AutoderefKind::Overloaded, deref_by_trait(table, ty)?))
+    }
+}
+
+// FIXME: replace uses of this with Autoderef above
+pub fn autoderef<'a>(
+    db: &'a dyn HirDatabase,
+    env: Arc<TraitEnvironment>,
+    ty: Canonical<Ty>,
+) -> impl Iterator<Item = Canonical<Ty>> + 'a {
+    let mut table = InferenceTable::new(db, env);
+    let ty = table.instantiate_canonical(ty);
+    let mut autoderef = Autoderef::new(&mut table, ty);
+    let mut v = Vec::new();
+    while let Some((ty, _steps)) = autoderef.next() {
+        v.push(autoderef.table.canonicalize(ty).value);
+    }
+    v.into_iter()
+}
+
+pub(crate) fn deref(table: &mut InferenceTable, ty: Ty) -> Option<Ty> {
+    let _p = profile::span("deref");
+    autoderef_step(table, ty).map(|(_, ty)| ty)
+}
+
+fn builtin_deref(ty: &Ty) -> Option<&Ty> {
+    match ty.kind(Interner) {
+        TyKind::Ref(.., ty) => Some(ty),
+        TyKind::Raw(.., ty) => Some(ty),
+        _ => None,
+    }
+}
+
+fn deref_by_trait(table: &mut InferenceTable, ty: Ty) -> Option<Ty> {
+    let _p = profile::span("deref_by_trait");
+    if table.resolve_ty_shallow(&ty).inference_var(Interner).is_some() {
+        // don't try to deref unknown variables
+        return None;
+    }
+
+    let db = table.db;
+    let deref_trait = db
+        .lang_item(table.trait_env.krate, SmolStr::new_inline("deref"))
+        .and_then(|l| l.as_trait())?;
+    let target = db.trait_data(deref_trait).associated_type_by_name(&name![Target])?;
+
+    let projection = {
+        let b = TyBuilder::assoc_type_projection(db, target);
+        if b.remaining() != 1 {
+            // the Target type + Deref trait should only have one generic parameter,
+            // namely Deref's Self type
+            return None;
+        }
+        b.push(ty).build()
+    };
+
+    // Check that the type implements Deref at all
+    let trait_ref = projection.trait_ref(db);
+    let implements_goal: Goal = trait_ref.cast(Interner);
+    table.try_obligation(implements_goal.clone())?;
+
+    table.register_obligation(implements_goal);
+
+    let result = table.normalize_projection_ty(projection);
+    Some(table.resolve_ty_shallow(&result))
+}