Auto merge of #12513 - Veykril:ty-utils, r=Veykril

internal: Simplify `hir_ty::utils`

4 files changed, 48 insertions, 69 deletions

diff --git a/crates/hir-def/src/data.rs b/crates/hir-def/src/data.rs
index 3ef10297241..f2d8318f7d7 100644
--- a/crates/hir-def/src/data.rs
+++ b/crates/hir-def/src/data.rs
@@ -28,7 +28,7 @@ pub struct FunctionData {
     pub attrs: Attrs,
     pub visibility: RawVisibility,
     pub abi: Option<Interned<str>>,
-    pub legacy_const_generics_indices: Vec<u32>,
+    pub legacy_const_generics_indices: Box<[u32]>,
     flags: FnFlags,
 }
 
@@ -131,7 +131,7 @@ impl FunctionData {
     }
 }
 
-fn parse_rustc_legacy_const_generics(tt: &tt::Subtree) -> Vec<u32> {
+fn parse_rustc_legacy_const_generics(tt: &tt::Subtree) -> Box<[u32]> {
     let mut indices = Vec::new();
     for args in tt.token_trees.chunks(2) {
         match &args[0] {
@@ -150,7 +150,7 @@ fn parse_rustc_legacy_const_generics(tt: &tt::Subtree) -> Vec<u32> {
         }
     }
 
-    indices
+    indices.into_boxed_slice()
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
diff --git a/crates/hir-def/src/lib.rs b/crates/hir-def/src/lib.rs
index 974a2ab8f25..4431d1b3c81 100644
--- a/crates/hir-def/src/lib.rs
+++ b/crates/hir-def/src/lib.rs
@@ -356,8 +356,8 @@ impl From<TypeParamId> for TypeOrConstParamId {
     }
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 /// A TypeOrConstParamId with an invariant that it actually belongs to a const
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct ConstParamId(TypeOrConstParamId);
 
 impl ConstParamId {
diff --git a/crates/hir-ty/src/infer/expr.rs b/crates/hir-ty/src/infer/expr.rs
index 2e645bf52ba..8be236421fb 100644
--- a/crates/hir-ty/src/infer/expr.rs
+++ b/crates/hir-ty/src/infer/expr.rs
@@ -1211,28 +1211,28 @@ impl<'a> InferenceContext<'a> {
     }
 
     /// Returns the argument indices to skip.
-    fn check_legacy_const_generics(&mut self, callee: Ty, args: &[ExprId]) -> Vec<u32> {
+    fn check_legacy_const_generics(&mut self, callee: Ty, args: &[ExprId]) -> Box<[u32]> {
         let (func, subst) = match callee.kind(Interner) {
             TyKind::FnDef(fn_id, subst) => {
                 let callable = CallableDefId::from_chalk(self.db, *fn_id);
                 let func = match callable {
                     CallableDefId::FunctionId(f) => f,
-                    _ => return Vec::new(),
+                    _ => return Default::default(),
                 };
                 (func, subst)
             }
-            _ => return Vec::new(),
+            _ => return Default::default(),
         };
 
         let data = self.db.function_data(func);
         if data.legacy_const_generics_indices.is_empty() {
-            return Vec::new();
+            return Default::default();
         }
 
         // only use legacy const generics if the param count matches with them
         if data.params.len() + data.legacy_const_generics_indices.len() != args.len() {
             if args.len() <= data.params.len() {
-                return Vec::new();
+                return Default::default();
             } else {
                 // there are more parameters than there should be without legacy
                 // const params; use them
diff --git a/crates/hir-ty/src/utils.rs b/crates/hir-ty/src/utils.rs
index fb39e6095c0..e608f857741 100644
--- a/crates/hir-ty/src/utils.rs
+++ b/crates/hir-ty/src/utils.rs
@@ -177,21 +177,19 @@ pub(crate) fn generics(db: &dyn DefDatabase, def: GenericDefId) -> Generics {
     let parent_generics = parent_generic_def(db, def).map(|def| Box::new(generics(db, def)));
     if parent_generics.is_some() && matches!(def, GenericDefId::TypeAliasId(_)) {
         let params = db.generic_params(def);
-        if params
-            .type_or_consts
-            .iter()
-            .any(|(_, x)| matches!(x, TypeOrConstParamData::ConstParamData(_)))
-        {
+        let has_consts =
+            params.iter().any(|(_, x)| matches!(x, TypeOrConstParamData::ConstParamData(_)));
+        return if has_consts {
             // XXX: treat const generic associated types as not existing to avoid crashes (#11769)
             //
             // Chalk expects the inner associated type's parameters to come
             // *before*, not after the trait's generics as we've always done it.
             // Adapting to this requires a larger refactoring
             cov_mark::hit!(ignore_gats);
-            return Generics { def, params: Interned::new(Default::default()), parent_generics };
+            Generics { def, params: Interned::new(Default::default()), parent_generics }
         } else {
-            return Generics { def, params, parent_generics };
-        }
+            Generics { def, params, parent_generics }
+        };
     }
     Generics { def, params: db.generic_params(def), parent_generics }
 }
@@ -219,68 +217,46 @@ impl Generics {
     pub(crate) fn iter<'a>(
         &'a self,
     ) -> impl DoubleEndedIterator<Item = (TypeOrConstParamId, &'a TypeOrConstParamData)> + 'a {
-        self.parent_generics
-            .as_ref()
+        let to_toc_id = |it: &'a Generics| {
+            move |(local_id, p)| (TypeOrConstParamId { parent: it.def, local_id }, p)
+        };
+        self.parent_generics()
             .into_iter()
-            .flat_map(|it| {
-                it.params
-                    .iter()
-                    .map(move |(local_id, p)| (TypeOrConstParamId { parent: it.def, local_id }, p))
-            })
-            .chain(
-                self.params.iter().map(move |(local_id, p)| {
-                    (TypeOrConstParamId { parent: self.def, local_id }, p)
-                }),
-            )
+            .flat_map(move |it| it.params.iter().map(to_toc_id(it)))
+            .chain(self.params.iter().map(to_toc_id(self)))
     }
 
     /// Iterator over types and const params of parent.
     pub(crate) fn iter_parent<'a>(
         &'a self,
     ) -> impl Iterator<Item = (TypeOrConstParamId, &'a TypeOrConstParamData)> + 'a {
-        self.parent_generics.as_ref().into_iter().flat_map(|it| {
-            it.params
-                .type_or_consts
-                .iter()
-                .map(move |(local_id, p)| (TypeOrConstParamId { parent: it.def, local_id }, p))
+        self.parent_generics().into_iter().flat_map(|it| {
+            let to_toc_id =
+                move |(local_id, p)| (TypeOrConstParamId { parent: it.def, local_id }, p);
+            it.params.iter().map(to_toc_id)
         })
     }
 
     pub(crate) fn len(&self) -> usize {
-        self.len_split().0
-    }
-
-    /// (total, parents, child)
-    pub(crate) fn len_split(&self) -> (usize, usize, usize) {
-        let parent = self.parent_generics.as_ref().map_or(0, |p| p.len());
+        let parent = self.parent_generics().map_or(0, Generics::len);
         let child = self.params.type_or_consts.len();
-        (parent + child, parent, child)
+        parent + child
     }
 
     /// (parent total, self param, type param list, const param list, impl trait)
     pub(crate) fn provenance_split(&self) -> (usize, usize, usize, usize, usize) {
-        let parent = self.parent_generics.as_ref().map_or(0, |p| p.len());
-        let self_params = self
-            .params
-            .iter()
-            .filter_map(|x| x.1.type_param())
-            .filter(|p| p.provenance == TypeParamProvenance::TraitSelf)
-            .count();
-        let type_params = self
-            .params
-            .type_or_consts
-            .iter()
-            .filter_map(|x| x.1.type_param())
-            .filter(|p| p.provenance == TypeParamProvenance::TypeParamList)
-            .count();
+        let ty_iter = || self.params.iter().filter_map(|x| x.1.type_param());
+
+        let self_params =
+            ty_iter().filter(|p| p.provenance == TypeParamProvenance::TraitSelf).count();
+        let type_params =
+            ty_iter().filter(|p| p.provenance == TypeParamProvenance::TypeParamList).count();
+        let impl_trait_params =
+            ty_iter().filter(|p| p.provenance == TypeParamProvenance::ArgumentImplTrait).count();
         let const_params = self.params.iter().filter_map(|x| x.1.const_param()).count();
-        let impl_trait_params = self
-            .params
-            .iter()
-            .filter_map(|x| x.1.type_param())
-            .filter(|p| p.provenance == TypeParamProvenance::ArgumentImplTrait)
-            .count();
-        (parent, self_params, type_params, const_params, impl_trait_params)
+
+        let parent_len = self.parent_generics().map_or(0, Generics::len);
+        (parent_len, self_params, type_params, const_params, impl_trait_params)
     }
 
     pub(crate) fn param_idx(&self, param: TypeOrConstParamId) -> Option<usize> {
@@ -291,18 +267,21 @@ impl Generics {
         if param.parent == self.def {
             let (idx, (_local_id, data)) = self
                 .params
-                .type_or_consts
                 .iter()
                 .enumerate()
                 .find(|(_, (idx, _))| *idx == param.local_id)
                 .unwrap();
-            let (_total, parent_len, _child) = self.len_split();
+            let parent_len = self.parent_generics().map_or(0, Generics::len);
             Some((parent_len + idx, data))
         } else {
-            self.parent_generics.as_ref().and_then(|g| g.find_param(param))
+            self.parent_generics().and_then(|g| g.find_param(param))
         }
     }
 
+    fn parent_generics(&self) -> Option<&Generics> {
+        self.parent_generics.as_ref().map(|it| &**it)
+    }
+
     /// Returns a Substitution that replaces each parameter by a bound variable.
     pub(crate) fn bound_vars_subst(
         &self,
@@ -377,10 +356,10 @@ pub fn is_fn_unsafe_to_call(db: &dyn HirDatabase, func: FunctionId) -> bool {
             // Function in an `extern` block are always unsafe to call, except when it has
             // `"rust-intrinsic"` ABI there are a few exceptions.
             let id = block.lookup(db.upcast()).id;
-            match id.item_tree(db.upcast())[id.value].abi.as_deref() {
-                Some("rust-intrinsic") => is_intrinsic_fn_unsafe(&data.name),
-                _ => true,
-            }
+            !matches!(
+                id.item_tree(db.upcast())[id.value].abi.as_deref(),
+                Some("rust-intrinsic") if !is_intrinsic_fn_unsafe(&data.name)
+            )
         }
         _ => false,
     }