10 files changed, 430 insertions, 31 deletions

diff --git a/crates/ra_hir/src/nameres.rs b/crates/ra_hir/src/nameres.rs
index bd920bfea..8067b8415 100644
--- a/crates/ra_hir/src/nameres.rs
+++ b/crates/ra_hir/src/nameres.rs
@@ -297,7 +297,14 @@ where
             );
             (res, if res.is_none() { ReachedFixedPoint::No } else { ReachedFixedPoint::Yes })
         } else {
-            self.result.resolve_path_fp(self.db, ResolveMode::Import, original_module, &import.path)
+            let res = self.result.resolve_path_fp(
+                self.db,
+                ResolveMode::Import,
+                original_module,
+                &import.path,
+            );
+
+            (res.resolved_def, res.reached_fixedpoint)
         };
 
         if reached_fixedpoint != ReachedFixedPoint::Yes {
@@ -435,6 +442,27 @@ where
     }
 }
 
+#[derive(Debug, Clone)]
+struct ResolvePathResult {
+    resolved_def: PerNs<ModuleDef>,
+    segment_index: Option<usize>,
+    reached_fixedpoint: ReachedFixedPoint,
+}
+
+impl ResolvePathResult {
+    fn empty(reached_fixedpoint: ReachedFixedPoint) -> ResolvePathResult {
+        ResolvePathResult::with(PerNs::none(), reached_fixedpoint, None)
+    }
+
+    fn with(
+        resolved_def: PerNs<ModuleDef>,
+        reached_fixedpoint: ReachedFixedPoint,
+        segment_index: Option<usize>,
+    ) -> ResolvePathResult {
+        ResolvePathResult { resolved_def, reached_fixedpoint, segment_index }
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 enum ResolveMode {
     Import,
@@ -468,8 +496,9 @@ impl ItemMap {
         db: &impl PersistentHirDatabase,
         original_module: Module,
         path: &Path,
-    ) -> PerNs<ModuleDef> {
-        self.resolve_path_fp(db, ResolveMode::Other, original_module, path).0
+    ) -> (PerNs<ModuleDef>, Option<usize>) {
+        let res = self.resolve_path_fp(db, ResolveMode::Other, original_module, path);
+        (res.resolved_def, res.segment_index)
     }
 
     fn resolve_in_prelude(
@@ -534,7 +563,7 @@ impl ItemMap {
         mode: ResolveMode,
         original_module: Module,
         path: &Path,
-    ) -> (PerNs<ModuleDef>, ReachedFixedPoint) {
+    ) -> ResolvePathResult {
         let mut segments = path.segments.iter().enumerate();
         let mut curr_per_ns: PerNs<ModuleDef> = match path.kind {
             PathKind::Crate => PerNs::types(original_module.crate_root(db).into()),
@@ -549,7 +578,7 @@ impl ItemMap {
             {
                 let segment = match segments.next() {
                     Some((_, segment)) => segment,
-                    None => return (PerNs::none(), ReachedFixedPoint::Yes),
+                    None => return ResolvePathResult::empty(ReachedFixedPoint::Yes),
                 };
                 log::debug!("resolving {:?} in crate root (+ extern prelude)", segment);
                 self.resolve_name_in_crate_root_or_extern_prelude(
@@ -561,7 +590,7 @@ impl ItemMap {
             PathKind::Plain => {
                 let segment = match segments.next() {
                     Some((_, segment)) => segment,
-                    None => return (PerNs::none(), ReachedFixedPoint::Yes),
+                    None => return ResolvePathResult::empty(ReachedFixedPoint::Yes),
                 };
                 log::debug!("resolving {:?} in module", segment);
                 self.resolve_name_in_module(db, original_module, &segment.name)
@@ -571,20 +600,20 @@ impl ItemMap {
                     PerNs::types(p.into())
                 } else {
                     log::debug!("super path in root module");
-                    return (PerNs::none(), ReachedFixedPoint::Yes);
+                    return ResolvePathResult::empty(ReachedFixedPoint::Yes);
                 }
             }
             PathKind::Abs => {
                 // 2018-style absolute path -- only extern prelude
                 let segment = match segments.next() {
                     Some((_, segment)) => segment,
-                    None => return (PerNs::none(), ReachedFixedPoint::Yes),
+                    None => return ResolvePathResult::empty(ReachedFixedPoint::Yes),
                 };
                 if let Some(def) = self.extern_prelude.get(&segment.name) {
                     log::debug!("absolute path {:?} resolved to crate {:?}", path, def);
                     PerNs::types(*def)
                 } else {
-                    return (PerNs::none(), ReachedFixedPoint::No); // extern crate declarations can add to the extern prelude
+                    return ResolvePathResult::empty(ReachedFixedPoint::No); // extern crate declarations can add to the extern prelude
                 }
             }
         };
@@ -598,7 +627,7 @@ impl ItemMap {
                     // (don't break here because `curr_per_ns` might contain
                     // something in the value namespace, and it would be wrong
                     // to return that)
-                    return (PerNs::none(), ReachedFixedPoint::No);
+                    return ResolvePathResult::empty(ReachedFixedPoint::No);
                 }
             };
             // resolve segment in curr
@@ -612,15 +641,15 @@ impl ItemMap {
                         };
                         log::debug!("resolving {:?} in other crate", path);
                         let item_map = db.item_map(module.krate);
-                        let def = item_map.resolve_path(db, *module, &path);
-                        return (def, ReachedFixedPoint::Yes);
+                        let (def, s) = item_map.resolve_path(db, *module, &path);
+                        return ResolvePathResult::with(def, ReachedFixedPoint::Yes, s);
                     }
 
                     match self[module.module_id].items.get(&segment.name) {
                         Some(res) if !res.def.is_none() => res.def,
                         _ => {
                             log::debug!("path segment {:?} not found", segment.name);
-                            return (PerNs::none(), ReachedFixedPoint::No);
+                            return ResolvePathResult::empty(ReachedFixedPoint::No);
                         }
                     }
                 }
@@ -629,23 +658,33 @@ impl ItemMap {
                     tested_by!(item_map_enum_importing);
                     match e.variant(db, &segment.name) {
                         Some(variant) => PerNs::both(variant.into(), variant.into()),
-                        None => PerNs::none(),
+                        None => {
+                            return ResolvePathResult::with(
+                                PerNs::types((*e).into()),
+                                ReachedFixedPoint::Yes,
+                                Some(i),
+                            );
+                        }
                     }
                 }
-                _ => {
+                s => {
                     // could be an inherent method call in UFCS form
-                    // (`Struct::method`), or some other kind of associated
-                    // item... Which we currently don't handle (TODO)
+                    // (`Struct::method`), or some other kind of associated item
                     log::debug!(
                         "path segment {:?} resolved to non-module {:?}, but is not last",
                         segment.name,
                         curr,
                     );
-                    return (PerNs::none(), ReachedFixedPoint::Yes);
+
+                    return ResolvePathResult::with(
+                        PerNs::types((*s).into()),
+                        ReachedFixedPoint::Yes,
+                        Some(i),
+                    );
                 }
             };
         }
-        (curr_per_ns, ReachedFixedPoint::Yes)
+        ResolvePathResult::with(curr_per_ns, ReachedFixedPoint::Yes, None)
     }
 }
 
diff --git a/crates/ra_hir/src/resolve.rs b/crates/ra_hir/src/resolve.rs
index 91a531801..57e7d0b9a 100644
--- a/crates/ra_hir/src/resolve.rs
+++ b/crates/ra_hir/src/resolve.rs
@@ -33,6 +33,67 @@ pub(crate) struct ExprScope {
 }
 
 #[derive(Debug, Clone)]
+pub(crate) struct PathResult {
+    /// The actual path resolution
+    resolution: PerNs<Resolution>,
+    /// The first index in the path that we
+    /// were unable to resolve.
+    /// When path is fully resolved, this is 0.
+    remaining_index: usize,
+}
+
+impl PathResult {
+    /// Returns the remaining index in the result
+    /// returns None if the path was fully resolved
+    pub(crate) fn remaining_index(&self) -> Option<usize> {
+        if self.remaining_index > 0 {
+            Some(self.remaining_index)
+        } else {
+            None
+        }
+    }
+
+    /// Consumes `PathResult` and returns the contained `PerNs<Resolution>`
+    /// if the path was fully resolved, meaning we have no remaining items
+    pub(crate) fn into_fully_resolved(self) -> PerNs<Resolution> {
+        if self.is_fully_resolved() {
+            self.resolution
+        } else {
+            PerNs::none()
+        }
+    }
+
+    /// Consumes `PathResult` and returns the resolution and the
+    /// remaining_index as a tuple.
+    pub(crate) fn into_inner(self) -> (PerNs<Resolution>, Option<usize>) {
+        let index = self.remaining_index();
+        (self.resolution, index)
+    }
+
+    /// Path is fully resolved when `remaining_index` is none
+    /// and the resolution contains anything
+    pub(crate) fn is_fully_resolved(&self) -> bool {
+        !self.resolution.is_none() && self.remaining_index().is_none()
+    }
+
+    fn empty() -> PathResult {
+        PathResult { resolution: PerNs::none(), remaining_index: 0 }
+    }
+
+    fn from_resolution(res: PerNs<Resolution>) -> PathResult {
+        PathResult::from_resolution_with_index(res, 0)
+    }
+
+    fn from_resolution_with_index(res: PerNs<Resolution>, remaining_index: usize) -> PathResult {
+        if res.is_none() {
+            PathResult::empty()
+        } else {
+            PathResult { resolution: res, remaining_index }
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
 pub(crate) enum Scope {
     /// All the items and imported names of a module
     ModuleScope(ModuleItemMap),
@@ -67,21 +128,37 @@ impl Resolver {
         resolution
     }
 
-    pub fn resolve_path(&self, db: &impl HirDatabase, path: &Path) -> PerNs<Resolution> {
+    /// Returns the resolved path segments
+    /// Which may be fully resolved, empty or partially resolved.
+    pub(crate) fn resolve_path_segments(&self, db: &impl HirDatabase, path: &Path) -> PathResult {
         if let Some(name) = path.as_ident() {
-            self.resolve_name(db, name)
+            PathResult::from_resolution(self.resolve_name(db, name))
         } else if path.is_self() {
-            self.resolve_name(db, &Name::self_param())
+            PathResult::from_resolution(self.resolve_name(db, &Name::self_param()))
         } else {
             let (item_map, module) = match self.module() {
                 Some(m) => m,
-                _ => return PerNs::none(),
+                _ => return PathResult::empty(),
             };
-            let module_res = item_map.resolve_path(db, module, path);
-            module_res.map(Resolution::Def)
+            let (module_res, segment_index) = item_map.resolve_path(db, module, path);
+
+            let def = module_res.map(Resolution::Def);
+
+            if let Some(index) = segment_index {
+                PathResult::from_resolution_with_index(def, index)
+            } else {
+                PathResult::from_resolution(def)
+            }
         }
     }
 
+    /// Returns the fully resolved path if we were able to resolve it.
+    /// otherwise returns `PerNs::none`
+    pub fn resolve_path(&self, db: &impl HirDatabase, path: &Path) -> PerNs<Resolution> {
+        // into_fully_resolved() returns the fully resolved path or PerNs::none() otherwise
+        self.resolve_path_segments(db, path).into_fully_resolved()
+    }
+
     pub fn all_names(&self, db: &impl HirDatabase) -> FxHashMap<Name, PerNs<Resolution>> {
         let mut names = FxHashMap::default();
         for scope in self.scopes.iter().rev() {
diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index 1a3e1994f..ae595c16d 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -37,7 +37,7 @@ use crate::{
     FnSignature, ModuleDef, AdtDef,
     HirDatabase,
     type_ref::{TypeRef, Mutability},
-    name::KnownName,
+    name::{KnownName},
     expr::{Body, Expr, BindingAnnotation, Literal, ExprId, Pat, PatId, UnaryOp, BinaryOp, Statement, FieldPat, self},
     generics::GenericParams,
     path::{ GenericArgs, GenericArg},
@@ -1166,15 +1166,55 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
     }
 
     fn infer_path_expr(&mut self, resolver: &Resolver, path: &Path) -> Option<Ty> {
-        let resolved = resolver.resolve_path(self.db, &path).take_values()?;
+        let resolved = resolver.resolve_path_segments(self.db, &path);
+
+        let (def, remaining_index) = resolved.into_inner();
+
+        // if the remaining_index is None, we expect the path
+        // to be fully resolved, in this case we continue with
+        // the default by attempting to `take_values´ from the resolution.
+        // Otherwise the path was partially resolved, which means
+        // we might have resolved into a type for which
+        // we may find some associated item starting at the
+        // path.segment pointed to by `remaining_index´
+        let resolved =
+            if remaining_index.is_none() { def.take_values()? } else { def.take_types()? };
+
         match resolved {
             Resolution::Def(def) => {
                 let typable: Option<TypableDef> = def.into();
                 let typable = typable?;
-                let substs = Ty::substs_from_path(self.db, &self.resolver, path, typable);
-                let ty = self.db.type_for_def(typable, Namespace::Values).apply_substs(substs);
-                let ty = self.insert_type_vars(ty);
-                Some(ty)
+
+                if let Some(remaining_index) = remaining_index {
+                    let ty = self.db.type_for_def(typable, Namespace::Types);
+                    // TODO: Keep resolving the segments
+                    // if we have more segments to process
+                    let segment = &path.segments[remaining_index];
+
+                    // Attempt to find an impl_item for the type which has a name matching
+                    // the current segment
+                    let ty = ty.iterate_impl_items(self.db, |item| match item {
+                        crate::ImplItem::Method(func) => {
+                            let sig = func.signature(self.db);
+                            if segment.name == *sig.name() {
+                                return Some(type_for_fn(self.db, func));
+                            }
+                            None
+                        }
+
+                        // TODO: Resolve associated const
+                        crate::ImplItem::Const(_) => None,
+
+                        // TODO: Resolve associated types
+                        crate::ImplItem::Type(_) => None,
+                    });
+                    ty
+                } else {
+                    let substs = Ty::substs_from_path(self.db, &self.resolver, path, typable);
+                    let ty = self.db.type_for_def(typable, Namespace::Values).apply_substs(substs);
+                    let ty = self.insert_type_vars(ty);
+                    Some(ty)
+                }
             }
             Resolution::LocalBinding(pat) => {
                 let ty = self.type_of_pat.get(pat)?;
diff --git a/crates/ra_hir/src/ty/snapshots/tests__infer_associated_const.snap b/crates/ra_hir/src/ty/snapshots/tests__infer_associated_const.snap
new file mode 100644
index 000000000..131d1fa16
--- /dev/null
+++ b/crates/ra_hir/src/ty/snapshots/tests__infer_associated_const.snap
@@ -0,0 +1,14 @@
+---
+created: "2019-02-21T21:51:46.497925200Z"
+creator: [email protected]
+source: crates/ra_hir/src/ty/tests.rs
+expression: "&result"
+---
+[227; 305) '{     ...:ID; }': ()
+[237; 238) 'x': [unknown]
+[241; 252) 'Struct::FOO': [unknown]
+[262; 263) 'y': [unknown]
+[266; 275) 'Enum::BAR': [unknown]
+[285; 286) 'z': [unknown]
+[289; 302) 'TraitTest::ID': [unknown]
+
diff --git a/crates/ra_hir/src/ty/snapshots/tests__infer_associated_method_enum.snap b/crates/ra_hir/src/ty/snapshots/tests__infer_associated_method_enum.snap
new file mode 100644
index 000000000..8f27af88c
--- /dev/null
+++ b/crates/ra_hir/src/ty/snapshots/tests__infer_associated_method_enum.snap
@@ -0,0 +1,20 @@
+---
+created: "2019-02-20T11:04:56.553382800Z"
+creator: [email protected]
+source: crates/ra_hir/src/ty/tests.rs
+expression: "&result"
+---
+[48; 68) '{     ...     }': A
+[58; 62) 'A::B': A
+[89; 109) '{     ...     }': A
+[99; 103) 'A::C': A
+[122; 179) '{     ...  c; }': ()
+[132; 133) 'a': A
+[136; 140) 'A::b': fn b() -> A
+[136; 142) 'A::b()': A
+[148; 149) 'a': A
+[159; 160) 'c': A
+[163; 167) 'A::c': fn c() -> A
+[163; 169) 'A::c()': A
+[175; 176) 'c': A
+
diff --git a/crates/ra_hir/src/ty/snapshots/tests__infer_associated_method_generics.snap b/crates/ra_hir/src/ty/snapshots/tests__infer_associated_method_generics.snap
new file mode 100644
index 000000000..fe5d6590e
--- /dev/null
+++ b/crates/ra_hir/src/ty/snapshots/tests__infer_associated_method_generics.snap
@@ -0,0 +1,16 @@
+---
+created: "2019-02-21T10:25:18.568887300Z"
+creator: [email protected]
+source: crates/ra_hir/src/ty/tests.rs
+expression: "&result"
+---
+[64; 67) 'val': T
+[82; 109) '{     ...     }': Gen<T>
+[92; 103) 'Gen { val }': Gen<T>
+[98; 101) 'val': T
+[123; 155) '{     ...32); }': ()
+[133; 134) 'a': Gen<[unknown]>
+[137; 146) 'Gen::make': fn make<[unknown]>(T) -> Gen<T>
+[137; 152) 'Gen::make(0u32)': Gen<[unknown]>
+[147; 151) '0u32': u32
+
diff --git a/crates/ra_hir/src/ty/snapshots/tests__infer_associated_method_struct.snap b/crates/ra_hir/src/ty/snapshots/tests__infer_associated_method_struct.snap
new file mode 100644
index 000000000..29ca9b0ea
--- /dev/null
+++ b/crates/ra_hir/src/ty/snapshots/tests__infer_associated_method_struct.snap
@@ -0,0 +1,16 @@
+---
+created: "2019-02-20T11:04:56.553382800Z"
+creator: [email protected]
+source: crates/ra_hir/src/ty/tests.rs
+expression: "&result"
+---
+[50; 76) '{     ...     }': A
+[60; 70) 'A { x: 0 }': A
+[67; 68) '0': u32
+[89; 123) '{     ...a.x; }': ()
+[99; 100) 'a': A
+[103; 109) 'A::new': fn new() -> A
+[103; 111) 'A::new()': A
+[117; 118) 'a': A
+[117; 120) 'a.x': u32
+
diff --git a/crates/ra_hir/src/ty/snapshots/tests__infer_associated_method_with_modules.snap b/crates/ra_hir/src/ty/snapshots/tests__infer_associated_method_with_modules.snap
new file mode 100644
index 000000000..6584bef39
--- /dev/null
+++ b/crates/ra_hir/src/ty/snapshots/tests__infer_associated_method_with_modules.snap
@@ -0,0 +1,23 @@
+---
+created: "2019-02-21T08:55:53.926725400Z"
+creator: [email protected]
+source: crates/ra_hir/src/ty/tests.rs
+expression: "&result"
+---
+[56; 64) '{ A {} }': A
+[58; 62) 'A {}': A
+[126; 132) '{ 99 }': u32
+[128; 130) '99': u32
+[202; 210) '{ C {} }': C
+[204; 208) 'C {}': C
+[241; 325) '{     ...g(); }': ()
+[251; 252) 'x': A
+[255; 266) 'a::A::thing': fn thing() -> A
+[255; 268) 'a::A::thing()': A
+[278; 279) 'y': u32
+[282; 293) 'b::B::thing': fn thing() -> u32
+[282; 295) 'b::B::thing()': u32
+[305; 306) 'z': C
+[309; 320) 'c::C::thing': fn thing() -> C
+[309; 322) 'c::C::thing()': C
+
diff --git a/crates/ra_hir/src/ty/tests.rs b/crates/ra_hir/src/ty/tests.rs
index 3affcb4fe..f04e9109c 100644
--- a/crates/ra_hir/src/ty/tests.rs
+++ b/crates/ra_hir/src/ty/tests.rs
@@ -608,6 +608,140 @@ fn test() -> i128 {
 }
 
 #[test]
+fn infer_associated_const() {
+    check_inference(
+        "infer_associated_const",
+        r#"
+struct Struct;
+
+impl Struct {
+    const FOO: u32 = 1;
+}
+
+enum Enum;
+
+impl Enum {
+    const BAR: u32 = 2;
+}
+
+trait Trait {
+    const ID: u32;
+}
+
+struct TraitTest;
+
+impl Trait for TraitTest {
+    const ID: u32 = 5;
+}
+
+fn test() {
+    let x = Struct::FOO;
+    let y = Enum::BAR;
+    let z = TraitTest::ID;
+}
+"#,
+    );
+}
+
+#[test]
+fn infer_associated_method_struct() {
+    check_inference(
+        "infer_associated_method_struct",
+        r#"
+struct A { x: u32 };
+
+impl A {
+    fn new() -> A {
+        A { x: 0 }
+    }
+}
+fn test() {
+    let a = A::new();
+    a.x;
+}
+"#,
+    );
+}
+
+#[test]
+fn infer_associated_method_enum() {
+    check_inference(
+        "infer_associated_method_enum",
+        r#"
+enum A { B, C };
+
+impl A {
+    pub fn b() -> A {
+        A::B
+    }
+    pub fn c() -> A {
+        A::C
+    }
+}
+fn test() {
+    let a = A::b();
+    a;
+    let c = A::c();
+    c;
+}
+"#,
+    );
+}
+
+#[test]
+fn infer_associated_method_with_modules() {
+    check_inference(
+        "infer_associated_method_with_modules",
+        r#"
+mod a {
+    struct A;
+    impl A { pub fn thing() -> A { A {} }}
+}
+
+mod b {
+    struct B;
+    impl B { pub fn thing() -> u32 { 99 }}
+
+    mod c {
+        struct C;
+        impl C { pub fn thing() -> C { C {} }}
+    }
+}
+use b::c;
+
+fn test() {
+    let x = a::A::thing();
+    let y = b::B::thing();
+    let z = c::C::thing();
+}
+"#,
+    );
+}
+
+#[test]
+#[ignore] // FIXME: After https://github.com/rust-analyzer/rust-analyzer/pull/866 is merged
+fn infer_associated_method_generics() {
+    check_inference(
+        "infer_associated_method_generics",
+        r#"
+struct Gen<T> {
+    val: T
+}
+
+impl<T> Gen<T> {
+    pub fn make(val: T) -> Gen<T> {
+        Gen { val }
+    }
+}
+
+fn test() {
+    let a = Gen::make(0u32);
+}
+"#,
+    );
+}
+
+#[test]
 fn no_panic_on_field_of_enum() {
     check_inference(
         "no_panic_on_field_of_enum",
diff --git a/crates/ra_ide_api/src/hover.rs b/crates/ra_ide_api/src/hover.rs
index a41c4e546..c62683ad4 100644
--- a/crates/ra_ide_api/src/hover.rs
+++ b/crates/ra_ide_api/src/hover.rs
@@ -240,4 +240,24 @@ mod tests {
         assert_eq!("usize", &type_name);
     }
 
+    #[test]
+    fn test_hover_infer_associated_method_result() {
+        let (analysis, position) = single_file_with_position(
+            "
+            struct Thing { x: u32 };
+
+            impl Thing {
+                fn new() -> Thing {
+                    Thing { x: 0 }
+                }
+            }
+
+            fn main() {
+                let foo_<|>test = Thing::new();
+            }
+            ",
+        );
+        let hover = analysis.hover(position).unwrap().unwrap();
+        assert_eq!(hover.info, "Thing");
+    }
 }