1 files changed, 201 insertions, 0 deletions

diff --git a/crates/ide_helpers/src/lib.rs b/crates/ide_helpers/src/lib.rs
new file mode 100644
index 000000000..069cb2bdd
--- /dev/null
+++ b/crates/ide_helpers/src/lib.rs
@@ -0,0 +1,201 @@
+use hir::{Crate, Enum, Module, ScopeDef, Semantics, Trait};
+use ide_db::RootDatabase;
+use syntax::ast::{self, make};
+
+pub mod insert_use;
+
+pub fn mod_path_to_ast(path: &hir::ModPath) -> ast::Path {
+    let _p = profile::span("mod_path_to_ast");
+    
+    let mut segments = Vec::new();
+    let mut is_abs = false;
+    match path.kind {
+        hir::PathKind::Plain => {}
+        hir::PathKind::Super(0) => segments.push(make::path_segment_self()),
+        hir::PathKind::Super(n) => segments.extend((0..n).map(|_| make::path_segment_super())),
+        hir::PathKind::DollarCrate(_) | hir::PathKind::Crate => {
+            segments.push(make::path_segment_crate())
+        }
+        hir::PathKind::Abs => is_abs = true,
+    }
+
+    segments.extend(
+        path.segments
+            .iter()
+            .map(|segment| make::path_segment(make::name_ref(&segment.to_string()))),
+    );
+    make::path_from_segments(segments, is_abs)
+}
+
+/// Helps with finding well-know things inside the standard library. This is
+/// somewhat similar to the known paths infra inside hir, but it different; We
+/// want to make sure that IDE specific paths don't become interesting inside
+/// the compiler itself as well.
+pub struct FamousDefs<'a, 'b>(pub &'a Semantics<'b, RootDatabase>, pub Option<Crate>);
+
+#[allow(non_snake_case)]
+impl FamousDefs<'_, '_> {
+    pub const FIXTURE: &'static str = r#"//- /libcore.rs crate:core
+pub mod convert {
+    pub trait From<T> {
+        fn from(t: T) -> Self;
+    }
+}
+
+pub mod default {
+    pub trait Default {
+       fn default() -> Self;
+    }
+}
+
+pub mod iter {
+    pub use self::traits::{collect::IntoIterator, iterator::Iterator};
+    mod traits {
+        pub(crate) mod iterator {
+            use crate::option::Option;
+            pub trait Iterator {
+                type Item;
+                fn next(&mut self) -> Option<Self::Item>;
+                fn by_ref(&mut self) -> &mut Self {
+                    self
+                }
+                fn take(self, n: usize) -> crate::iter::Take<Self> {
+                    crate::iter::Take { inner: self }
+                }
+            }
+
+            impl<I: Iterator> Iterator for &mut I {
+                type Item = I::Item;
+                fn next(&mut self) -> Option<I::Item> {
+                    (**self).next()
+                }
+            }
+        }
+        pub(crate) mod collect {
+            pub trait IntoIterator {
+                type Item;
+            }
+        }
+    }
+
+    pub use self::sources::*;
+    pub(crate) mod sources {
+        use super::Iterator;
+        use crate::option::Option::{self, *};
+        pub struct Repeat<A> {
+            element: A,
+        }
+
+        pub fn repeat<T>(elt: T) -> Repeat<T> {
+            Repeat { element: elt }
+        }
+
+        impl<A> Iterator for Repeat<A> {
+            type Item = A;
+
+            fn next(&mut self) -> Option<A> {
+                None
+            }
+        }
+    }
+
+    pub use self::adapters::*;
+    pub(crate) mod adapters {
+        use super::Iterator;
+        use crate::option::Option::{self, *};
+        pub struct Take<I> { pub(crate) inner: I }
+        impl<I> Iterator for Take<I> where I: Iterator {
+            type Item = <I as Iterator>::Item;
+            fn next(&mut self) -> Option<<I as Iterator>::Item> {
+                None
+            }
+        }
+    }
+}
+
+pub mod option {
+    pub enum Option<T> { None, Some(T)}
+}
+
+pub mod prelude {
+    pub use crate::{convert::From, iter::{IntoIterator, Iterator}, option::Option::{self, *}, default::Default};
+}
+#[prelude_import]
+pub use prelude::*;
+"#;
+
+    pub fn core(&self) -> Option<Crate> {
+        self.find_crate("core")
+    }
+
+    pub fn core_convert_From(&self) -> Option<Trait> {
+        self.find_trait("core:convert:From")
+    }
+
+    pub fn core_option_Option(&self) -> Option<Enum> {
+        self.find_enum("core:option:Option")
+    }
+
+    pub fn core_default_Default(&self) -> Option<Trait> {
+        self.find_trait("core:default:Default")
+    }
+
+    pub fn core_iter_Iterator(&self) -> Option<Trait> {
+        self.find_trait("core:iter:traits:iterator:Iterator")
+    }
+
+    pub fn core_iter(&self) -> Option<Module> {
+        self.find_module("core:iter")
+    }
+
+    fn find_trait(&self, path: &str) -> Option<Trait> {
+        match self.find_def(path)? {
+            hir::ScopeDef::ModuleDef(hir::ModuleDef::Trait(it)) => Some(it),
+            _ => None,
+        }
+    }
+
+    fn find_enum(&self, path: &str) -> Option<Enum> {
+        match self.find_def(path)? {
+            hir::ScopeDef::ModuleDef(hir::ModuleDef::Adt(hir::Adt::Enum(it))) => Some(it),
+            _ => None,
+        }
+    }
+
+    fn find_module(&self, path: &str) -> Option<Module> {
+        match self.find_def(path)? {
+            hir::ScopeDef::ModuleDef(hir::ModuleDef::Module(it)) => Some(it),
+            _ => None,
+        }
+    }
+
+    fn find_crate(&self, name: &str) -> Option<Crate> {
+        let krate = self.1?;
+        let db = self.0.db;
+        let res =
+            krate.dependencies(db).into_iter().find(|dep| dep.name.to_string() == name)?.krate;
+        Some(res)
+    }
+
+    fn find_def(&self, path: &str) -> Option<ScopeDef> {
+        let db = self.0.db;
+        let mut path = path.split(':');
+        let trait_ = path.next_back()?;
+        let std_crate = path.next()?;
+        let std_crate = self.find_crate(std_crate)?;
+        let mut module = std_crate.root_module(db);
+        for segment in path {
+            module = module.children(db).find_map(|child| {
+                let name = child.name(db)?;
+                if name.to_string() == segment {
+                    Some(child)
+                } else {
+                    None
+                }
+            })?;
+        }
+        let def =
+            module.scope(db, None).into_iter().find(|(name, _def)| name.to_string() == trait_)?.1;
+        Some(def)
+    }
+}