1 files changed, 351 insertions, 0 deletions

diff --git a/crates/hir_def/src/path.rs b/crates/hir_def/src/path.rs
new file mode 100644
index 000000000..74d26f08b
--- /dev/null
+++ b/crates/hir_def/src/path.rs
@@ -0,0 +1,351 @@
+//! A desugared representation of paths like `crate::foo` or `<Type as Trait>::bar`.
+mod lower;
+
+use std::{
+    fmt::{self, Display},
+    iter,
+    sync::Arc,
+};
+
+use crate::body::LowerCtx;
+use base_db::CrateId;
+use hir_expand::{
+    hygiene::Hygiene,
+    name::{AsName, Name},
+};
+use syntax::ast;
+
+use crate::{
+    type_ref::{TypeBound, TypeRef},
+    InFile,
+};
+
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ModPath {
+    pub kind: PathKind,
+    pub segments: Vec<Name>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum PathKind {
+    Plain,
+    /// `self::` is `Super(0)`
+    Super(u8),
+    Crate,
+    /// Absolute path (::foo)
+    Abs,
+    /// `$crate` from macro expansion
+    DollarCrate(CrateId),
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ImportAlias {
+    /// Unnamed alias, as in `use Foo as _;`
+    Underscore,
+    /// Named alias
+    Alias(Name),
+}
+
+impl ModPath {
+    pub fn from_src(path: ast::Path, hygiene: &Hygiene) -> Option<ModPath> {
+        lower::lower_path(path, hygiene).map(|it| it.mod_path)
+    }
+
+    pub fn from_segments(kind: PathKind, segments: impl IntoIterator<Item = Name>) -> ModPath {
+        let segments = segments.into_iter().collect::<Vec<_>>();
+        ModPath { kind, segments }
+    }
+
+    pub(crate) fn from_name_ref(name_ref: &ast::NameRef) -> ModPath {
+        name_ref.as_name().into()
+    }
+
+    /// Converts an `tt::Ident` into a single-identifier `Path`.
+    pub(crate) fn from_tt_ident(ident: &tt::Ident) -> ModPath {
+        ident.as_name().into()
+    }
+
+    /// Calls `cb` with all paths, represented by this use item.
+    pub(crate) fn expand_use_item(
+        item_src: InFile<ast::Use>,
+        hygiene: &Hygiene,
+        mut cb: impl FnMut(ModPath, &ast::UseTree, /* is_glob */ bool, Option<ImportAlias>),
+    ) {
+        if let Some(tree) = item_src.value.use_tree() {
+            lower::lower_use_tree(None, tree, hygiene, &mut cb);
+        }
+    }
+
+    /// Returns the number of segments in the path (counting special segments like `$crate` and
+    /// `super`).
+    pub fn len(&self) -> usize {
+        self.segments.len()
+            + match self.kind {
+                PathKind::Plain => 0,
+                PathKind::Super(i) => i as usize,
+                PathKind::Crate => 1,
+                PathKind::Abs => 0,
+                PathKind::DollarCrate(_) => 1,
+            }
+    }
+
+    pub fn is_ident(&self) -> bool {
+        self.kind == PathKind::Plain && self.segments.len() == 1
+    }
+
+    pub fn is_self(&self) -> bool {
+        self.kind == PathKind::Super(0) && self.segments.is_empty()
+    }
+
+    /// If this path is a single identifier, like `foo`, return its name.
+    pub fn as_ident(&self) -> Option<&Name> {
+        if self.kind != PathKind::Plain || self.segments.len() > 1 {
+            return None;
+        }
+        self.segments.first()
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Path {
+    /// Type based path like `<T>::foo`.
+    /// Note that paths like `<Type as Trait>::foo` are desugard to `Trait::<Self=Type>::foo`.
+    type_anchor: Option<Box<TypeRef>>,
+    mod_path: ModPath,
+    /// Invariant: the same len as `self.mod_path.segments`
+    generic_args: Vec<Option<Arc<GenericArgs>>>,
+}
+
+/// Generic arguments to a path segment (e.g. the `i32` in `Option<i32>`). This
+/// also includes bindings of associated types, like in `Iterator<Item = Foo>`.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct GenericArgs {
+    pub args: Vec<GenericArg>,
+    /// This specifies whether the args contain a Self type as the first
+    /// element. This is the case for path segments like `<T as Trait>`, where
+    /// `T` is actually a type parameter for the path `Trait` specifying the
+    /// Self type. Otherwise, when we have a path `Trait<X, Y>`, the Self type
+    /// is left out.
+    pub has_self_type: bool,
+    /// Associated type bindings like in `Iterator<Item = T>`.
+    pub bindings: Vec<AssociatedTypeBinding>,
+}
+
+/// An associated type binding like in `Iterator<Item = T>`.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct AssociatedTypeBinding {
+    /// The name of the associated type.
+    pub name: Name,
+    /// The type bound to this associated type (in `Item = T`, this would be the
+    /// `T`). This can be `None` if there are bounds instead.
+    pub type_ref: Option<TypeRef>,
+    /// Bounds for the associated type, like in `Iterator<Item:
+    /// SomeOtherTrait>`. (This is the unstable `associated_type_bounds`
+    /// feature.)
+    pub bounds: Vec<TypeBound>,
+}
+
+/// A single generic argument.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum GenericArg {
+    Type(TypeRef),
+    // or lifetime...
+}
+
+impl Path {
+    /// Converts an `ast::Path` to `Path`. Works with use trees.
+    #[deprecated = "Doesn't handle hygiene, don't add new calls, remove old ones"]
+    pub fn from_ast(path: ast::Path) -> Option<Path> {
+        lower::lower_path(path, &Hygiene::new_unhygienic())
+    }
+
+    /// Converts an `ast::Path` to `Path`. Works with use trees.
+    /// It correctly handles `$crate` based path from macro call.
+    pub fn from_src(path: ast::Path, hygiene: &Hygiene) -> Option<Path> {
+        lower::lower_path(path, hygiene)
+    }
+
+    /// Converts a known mod path to `Path`.
+    pub(crate) fn from_known_path(
+        path: ModPath,
+        generic_args: Vec<Option<Arc<GenericArgs>>>,
+    ) -> Path {
+        Path { type_anchor: None, mod_path: path, generic_args }
+    }
+
+    pub fn kind(&self) -> &PathKind {
+        &self.mod_path.kind
+    }
+
+    pub fn type_anchor(&self) -> Option<&TypeRef> {
+        self.type_anchor.as_deref()
+    }
+
+    pub fn segments(&self) -> PathSegments<'_> {
+        PathSegments {
+            segments: self.mod_path.segments.as_slice(),
+            generic_args: self.generic_args.as_slice(),
+        }
+    }
+
+    pub fn mod_path(&self) -> &ModPath {
+        &self.mod_path
+    }
+
+    pub fn qualifier(&self) -> Option<Path> {
+        if self.mod_path.is_ident() {
+            return None;
+        }
+        let res = Path {
+            type_anchor: self.type_anchor.clone(),
+            mod_path: ModPath {
+                kind: self.mod_path.kind.clone(),
+                segments: self.mod_path.segments[..self.mod_path.segments.len() - 1].to_vec(),
+            },
+            generic_args: self.generic_args[..self.generic_args.len() - 1].to_vec(),
+        };
+        Some(res)
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct PathSegment<'a> {
+    pub name: &'a Name,
+    pub args_and_bindings: Option<&'a GenericArgs>,
+}
+
+pub struct PathSegments<'a> {
+    segments: &'a [Name],
+    generic_args: &'a [Option<Arc<GenericArgs>>],
+}
+
+impl<'a> PathSegments<'a> {
+    pub const EMPTY: PathSegments<'static> = PathSegments { segments: &[], generic_args: &[] };
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+    pub fn len(&self) -> usize {
+        self.segments.len()
+    }
+    pub fn first(&self) -> Option<PathSegment<'a>> {
+        self.get(0)
+    }
+    pub fn last(&self) -> Option<PathSegment<'a>> {
+        self.get(self.len().checked_sub(1)?)
+    }
+    pub fn get(&self, idx: usize) -> Option<PathSegment<'a>> {
+        assert_eq!(self.segments.len(), self.generic_args.len());
+        let res = PathSegment {
+            name: self.segments.get(idx)?,
+            args_and_bindings: self.generic_args.get(idx).unwrap().as_ref().map(|it| &**it),
+        };
+        Some(res)
+    }
+    pub fn skip(&self, len: usize) -> PathSegments<'a> {
+        assert_eq!(self.segments.len(), self.generic_args.len());
+        PathSegments { segments: &self.segments[len..], generic_args: &self.generic_args[len..] }
+    }
+    pub fn take(&self, len: usize) -> PathSegments<'a> {
+        assert_eq!(self.segments.len(), self.generic_args.len());
+        PathSegments { segments: &self.segments[..len], generic_args: &self.generic_args[..len] }
+    }
+    pub fn iter(&self) -> impl Iterator<Item = PathSegment<'a>> {
+        self.segments.iter().zip(self.generic_args.iter()).map(|(name, args)| PathSegment {
+            name,
+            args_and_bindings: args.as_ref().map(|it| &**it),
+        })
+    }
+}
+
+impl GenericArgs {
+    pub(crate) fn from_ast(lower_ctx: &LowerCtx, node: ast::GenericArgList) -> Option<GenericArgs> {
+        lower::lower_generic_args(lower_ctx, node)
+    }
+
+    pub(crate) fn empty() -> GenericArgs {
+        GenericArgs { args: Vec::new(), has_self_type: false, bindings: Vec::new() }
+    }
+}
+
+impl From<Name> for Path {
+    fn from(name: Name) -> Path {
+        Path {
+            type_anchor: None,
+            mod_path: ModPath::from_segments(PathKind::Plain, iter::once(name)),
+            generic_args: vec![None],
+        }
+    }
+}
+
+impl From<Name> for ModPath {
+    fn from(name: Name) -> ModPath {
+        ModPath::from_segments(PathKind::Plain, iter::once(name))
+    }
+}
+
+impl Display for ModPath {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut first_segment = true;
+        let mut add_segment = |s| -> fmt::Result {
+            if !first_segment {
+                f.write_str("::")?;
+            }
+            first_segment = false;
+            f.write_str(s)?;
+            Ok(())
+        };
+        match self.kind {
+            PathKind::Plain => {}
+            PathKind::Super(n) => {
+                if n == 0 {
+                    add_segment("self")?;
+                }
+                for _ in 0..n {
+                    add_segment("super")?;
+                }
+            }
+            PathKind::Crate => add_segment("crate")?,
+            PathKind::Abs => add_segment("")?,
+            PathKind::DollarCrate(_) => add_segment("$crate")?,
+        }
+        for segment in &self.segments {
+            if !first_segment {
+                f.write_str("::")?;
+            }
+            first_segment = false;
+            write!(f, "{}", segment)?;
+        }
+        Ok(())
+    }
+}
+
+pub use hir_expand::name as __name;
+
+#[macro_export]
+macro_rules! __known_path {
+    (core::iter::IntoIterator) => {};
+    (core::result::Result) => {};
+    (core::ops::Range) => {};
+    (core::ops::RangeFrom) => {};
+    (core::ops::RangeFull) => {};
+    (core::ops::RangeTo) => {};
+    (core::ops::RangeToInclusive) => {};
+    (core::ops::RangeInclusive) => {};
+    (core::future::Future) => {};
+    (core::ops::Try) => {};
+    ($path:path) => {
+        compile_error!("Please register your known path in the path module")
+    };
+}
+
+#[macro_export]
+macro_rules! __path {
+    ($start:ident $(:: $seg:ident)*) => ({
+        $crate::__known_path!($start $(:: $seg)*);
+        $crate::path::ModPath::from_segments($crate::path::PathKind::Abs, vec![
+            $crate::path::__name![$start], $($crate::path::__name![$seg],)*
+        ])
+    });
+}
+
+pub use crate::__path as path;