1 files changed, 318 insertions, 0 deletions

diff --git a/crates/ra_hir/src/ty/lower.rs b/crates/ra_hir/src/ty/lower.rs
new file mode 100644
index 000000000..cc9e0fd40
--- /dev/null
+++ b/crates/ra_hir/src/ty/lower.rs
@@ -0,0 +1,318 @@
+//! Methods for lowering the HIR to types. There are two main cases here:
+//!
+//!  - Lowering a type reference like `&usize` or `Option<foo::bar::Baz>` to a
+//!    type: The entry point for this is `Ty::from_hir`.
+//!  - Building the type for an item: This happens through the `type_for_def` query.
+//!
+//! This usually involves resolving names, collecting generic arguments etc.
+
+use std::sync::Arc;
+
+use crate::{
+    Function, Struct, StructField, Enum, EnumVariant, Path, Name,
+    ModuleDef,
+    HirDatabase,
+    type_ref::TypeRef,
+    name::KnownName,
+    nameres::Namespace,
+    resolve::{Resolver, Resolution},
+    path::GenericArg,
+    generics::GenericParams,
+    adt::VariantDef,
+};
+use super::{Ty, primitive, FnSig, Substs};
+
+impl Ty {
+    pub(crate) fn from_hir(db: &impl HirDatabase, resolver: &Resolver, type_ref: &TypeRef) -> Self {
+        match type_ref {
+            TypeRef::Never => Ty::Never,
+            TypeRef::Tuple(inner) => {
+                let inner_tys =
+                    inner.iter().map(|tr| Ty::from_hir(db, resolver, tr)).collect::<Vec<_>>();
+                Ty::Tuple(inner_tys.into())
+            }
+            TypeRef::Path(path) => Ty::from_hir_path(db, resolver, path),
+            TypeRef::RawPtr(inner, mutability) => {
+                let inner_ty = Ty::from_hir(db, resolver, inner);
+                Ty::RawPtr(Arc::new(inner_ty), *mutability)
+            }
+            TypeRef::Array(inner) => {
+                let inner_ty = Ty::from_hir(db, resolver, inner);
+                Ty::Array(Arc::new(inner_ty))
+            }
+            TypeRef::Slice(inner) => {
+                let inner_ty = Ty::from_hir(db, resolver, inner);
+                Ty::Slice(Arc::new(inner_ty))
+            }
+            TypeRef::Reference(inner, mutability) => {
+                let inner_ty = Ty::from_hir(db, resolver, inner);
+                Ty::Ref(Arc::new(inner_ty), *mutability)
+            }
+            TypeRef::Placeholder => Ty::Unknown,
+            TypeRef::Fn(params) => {
+                let mut inner_tys =
+                    params.iter().map(|tr| Ty::from_hir(db, resolver, tr)).collect::<Vec<_>>();
+                let return_ty =
+                    inner_tys.pop().expect("TypeRef::Fn should always have at least return type");
+                let sig = FnSig { input: inner_tys, output: return_ty };
+                Ty::FnPtr(Arc::new(sig))
+            }
+            TypeRef::Error => Ty::Unknown,
+        }
+    }
+
+    pub(crate) fn from_hir_path(db: &impl HirDatabase, resolver: &Resolver, path: &Path) -> Self {
+        if let Some(name) = path.as_ident() {
+            // TODO handle primitive type names in resolver as well?
+            if let Some(int_ty) = primitive::UncertainIntTy::from_name(name) {
+                return Ty::Int(int_ty);
+            } else if let Some(float_ty) = primitive::UncertainFloatTy::from_name(name) {
+                return Ty::Float(float_ty);
+            } else if let Some(known) = name.as_known_name() {
+                match known {
+                    KnownName::Bool => return Ty::Bool,
+                    KnownName::Char => return Ty::Char,
+                    KnownName::Str => return Ty::Str,
+                    _ => {}
+                }
+            }
+        }
+
+        // Resolve the path (in type namespace)
+        let resolution = resolver.resolve_path(db, path).take_types();
+
+        let def = match resolution {
+            Some(Resolution::Def(def)) => def,
+            Some(Resolution::LocalBinding(..)) => {
+                // this should never happen
+                panic!("path resolved to local binding in type ns");
+            }
+            Some(Resolution::GenericParam(idx)) => {
+                return Ty::Param {
+                    idx,
+                    // TODO: maybe return name in resolution?
+                    name: path
+                        .as_ident()
+                        .expect("generic param should be single-segment path")
+                        .clone(),
+                };
+            }
+            Some(Resolution::SelfType(impl_block)) => {
+                return impl_block.target_ty(db);
+            }
+            None => return Ty::Unknown,
+        };
+
+        let typable: TypableDef = match def.into() {
+            None => return Ty::Unknown,
+            Some(it) => it,
+        };
+        let ty = db.type_for_def(typable, Namespace::Types);
+        let substs = Ty::substs_from_path(db, resolver, path, typable);
+        ty.apply_substs(substs)
+    }
+
+    /// Collect generic arguments from a path into a `Substs`. See also
+    /// `create_substs_for_ast_path` and `def_to_ty` in rustc.
+    pub(super) fn substs_from_path(
+        db: &impl HirDatabase,
+        resolver: &Resolver,
+        path: &Path,
+        resolved: TypableDef,
+    ) -> Substs {
+        let mut substs = Vec::new();
+        let last = path.segments.last().expect("path should have at least one segment");
+        let (def_generics, segment) = match resolved {
+            TypableDef::Function(func) => (func.generic_params(db), last),
+            TypableDef::Struct(s) => (s.generic_params(db), last),
+            TypableDef::Enum(e) => (e.generic_params(db), last),
+            TypableDef::EnumVariant(var) => {
+                // the generic args for an enum variant may be either specified
+                // on the segment referring to the enum, or on the segment
+                // referring to the variant. So `Option::<T>::None` and
+                // `Option::None::<T>` are both allowed (though the former is
+                // preferred). See also `def_ids_for_path_segments` in rustc.
+                let len = path.segments.len();
+                let segment = if len >= 2 && path.segments[len - 2].args_and_bindings.is_some() {
+                    // Option::<T>::None
+                    &path.segments[len - 2]
+                } else {
+                    // Option::None::<T>
+                    last
+                };
+                (var.parent_enum(db).generic_params(db), segment)
+            }
+        };
+        let parent_param_count = def_generics.count_parent_params();
+        substs.extend((0..parent_param_count).map(|_| Ty::Unknown));
+        if let Some(generic_args) = &segment.args_and_bindings {
+            // if args are provided, it should be all of them, but we can't rely on that
+            let param_count = def_generics.params.len();
+            for arg in generic_args.args.iter().take(param_count) {
+                match arg {
+                    GenericArg::Type(type_ref) => {
+                        let ty = Ty::from_hir(db, resolver, type_ref);
+                        substs.push(ty);
+                    }
+                }
+            }
+        }
+        // add placeholders for args that were not provided
+        // TODO: handle defaults
+        let supplied_params = substs.len();
+        for _ in supplied_params..def_generics.count_params_including_parent() {
+            substs.push(Ty::Unknown);
+        }
+        assert_eq!(substs.len(), def_generics.count_params_including_parent());
+        Substs(substs.into())
+    }
+}
+
+/// Build the declared type of an item. This depends on the namespace; e.g. for
+/// `struct Foo(usize)`, we have two types: The type of the struct itself, and
+/// the constructor function `(usize) -> Foo` which lives in the values
+/// namespace.
+pub(crate) fn type_for_def(db: &impl HirDatabase, def: TypableDef, ns: Namespace) -> Ty {
+    match (def, ns) {
+        (TypableDef::Function(f), Namespace::Values) => type_for_fn(db, f),
+        (TypableDef::Struct(s), Namespace::Types) => type_for_struct(db, s),
+        (TypableDef::Struct(s), Namespace::Values) => type_for_struct_constructor(db, s),
+        (TypableDef::Enum(e), Namespace::Types) => type_for_enum(db, e),
+        (TypableDef::EnumVariant(v), Namespace::Values) => type_for_enum_variant_constructor(db, v),
+
+        // 'error' cases:
+        (TypableDef::Function(_), Namespace::Types) => Ty::Unknown,
+        (TypableDef::Enum(_), Namespace::Values) => Ty::Unknown,
+        (TypableDef::EnumVariant(_), Namespace::Types) => Ty::Unknown,
+    }
+}
+
+/// Build the type of a specific field of a struct or enum variant.
+pub(crate) fn type_for_field(db: &impl HirDatabase, field: StructField) -> Ty {
+    let parent_def = field.parent_def(db);
+    let resolver = match parent_def {
+        VariantDef::Struct(it) => it.resolver(db),
+        VariantDef::EnumVariant(it) => it.parent_enum(db).resolver(db),
+    };
+    let var_data = parent_def.variant_data(db);
+    let type_ref = &var_data.fields().unwrap()[field.id].type_ref;
+    Ty::from_hir(db, &resolver, type_ref)
+}
+
+/// Build the declared type of a function. This should not need to look at the
+/// function body.
+fn type_for_fn(db: &impl HirDatabase, def: Function) -> Ty {
+    let signature = def.signature(db);
+    let resolver = def.resolver(db);
+    let generics = def.generic_params(db);
+    let name = def.name(db);
+    let input =
+        signature.params().iter().map(|tr| Ty::from_hir(db, &resolver, tr)).collect::<Vec<_>>();
+    let output = Ty::from_hir(db, &resolver, signature.ret_type());
+    let sig = Arc::new(FnSig { input, output });
+    let substs = make_substs(&generics);
+    Ty::FnDef { def: def.into(), sig, name, substs }
+}
+
+/// Build the type of a tuple struct constructor.
+fn type_for_struct_constructor(db: &impl HirDatabase, def: Struct) -> Ty {
+    let var_data = def.variant_data(db);
+    let fields = match var_data.fields() {
+        Some(fields) => fields,
+        None => return type_for_struct(db, def), // Unit struct
+    };
+    let resolver = def.resolver(db);
+    let generics = def.generic_params(db);
+    let name = def.name(db).unwrap_or_else(Name::missing);
+    let input = fields
+        .iter()
+        .map(|(_, field)| Ty::from_hir(db, &resolver, &field.type_ref))
+        .collect::<Vec<_>>();
+    let output = type_for_struct(db, def);
+    let sig = Arc::new(FnSig { input, output });
+    let substs = make_substs(&generics);
+    Ty::FnDef { def: def.into(), sig, name, substs }
+}
+
+/// Build the type of a tuple enum variant constructor.
+fn type_for_enum_variant_constructor(db: &impl HirDatabase, def: EnumVariant) -> Ty {
+    let var_data = def.variant_data(db);
+    let fields = match var_data.fields() {
+        Some(fields) => fields,
+        None => return type_for_enum(db, def.parent_enum(db)), // Unit variant
+    };
+    let resolver = def.parent_enum(db).resolver(db);
+    let generics = def.parent_enum(db).generic_params(db);
+    let name = def.name(db).unwrap_or_else(Name::missing);
+    let input = fields
+        .iter()
+        .map(|(_, field)| Ty::from_hir(db, &resolver, &field.type_ref))
+        .collect::<Vec<_>>();
+    let substs = make_substs(&generics);
+    let output = type_for_enum(db, def.parent_enum(db)).apply_substs(substs.clone());
+    let sig = Arc::new(FnSig { input, output });
+    Ty::FnDef { def: def.into(), sig, name, substs }
+}
+
+fn make_substs(generics: &GenericParams) -> Substs {
+    Substs(
+        generics
+            .params_including_parent()
+            .into_iter()
+            .map(|p| Ty::Param { idx: p.idx, name: p.name.clone() })
+            .collect::<Vec<_>>()
+            .into(),
+    )
+}
+
+fn type_for_struct(db: &impl HirDatabase, s: Struct) -> Ty {
+    let generics = s.generic_params(db);
+    Ty::Adt {
+        def_id: s.into(),
+        name: s.name(db).unwrap_or_else(Name::missing),
+        substs: make_substs(&generics),
+    }
+}
+
+fn type_for_enum(db: &impl HirDatabase, s: Enum) -> Ty {
+    let generics = s.generic_params(db);
+    Ty::Adt {
+        def_id: s.into(),
+        name: s.name(db).unwrap_or_else(Name::missing),
+        substs: make_substs(&generics),
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum TypableDef {
+    Function(Function),
+    Struct(Struct),
+    Enum(Enum),
+    EnumVariant(EnumVariant),
+}
+impl_froms!(TypableDef: Function, Struct, Enum, EnumVariant);
+
+impl From<ModuleDef> for Option<TypableDef> {
+    fn from(def: ModuleDef) -> Option<TypableDef> {
+        let res = match def {
+            ModuleDef::Function(f) => f.into(),
+            ModuleDef::Struct(s) => s.into(),
+            ModuleDef::Enum(e) => e.into(),
+            ModuleDef::EnumVariant(v) => v.into(),
+            ModuleDef::Const(_)
+            | ModuleDef::Static(_)
+            | ModuleDef::Module(_)
+            | ModuleDef::Trait(_)
+            | ModuleDef::Type(_) => return None,
+        };
+        Some(res)
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum CallableDef {
+    Function(Function),
+    Struct(Struct),
+    EnumVariant(EnumVariant),
+}
+impl_froms!(CallableDef: Function, Struct, EnumVariant);