Implement inline associated type bounds

Like `Iterator<Item: SomeTrait>`.

This is an unstable feature, but it's used in the standard library e.g. in the
definition of Flatten, so we can't get away with not implementing it :)

4 files changed, 51 insertions, 11 deletions

diff --git a/crates/ra_hir_def/src/data.rs b/crates/ra_hir_def/src/data.rs
index 56a20c5bd..b3c91fea2 100644
--- a/crates/ra_hir_def/src/data.rs
+++ b/crates/ra_hir_def/src/data.rs
@@ -15,7 +15,7 @@ use ra_syntax::ast::{
 use crate::{
     attr::Attrs,
     db::DefDatabase,
-    path::{path, GenericArgs, Path},
+    path::{path, AssociatedTypeBinding, GenericArgs, Path},
     src::HasSource,
     type_ref::{Mutability, TypeBound, TypeRef},
     visibility::RawVisibility,
@@ -95,7 +95,11 @@ fn desugar_future_path(orig: TypeRef) -> Path {
     let path = path![std::future::Future];
     let mut generic_args: Vec<_> = std::iter::repeat(None).take(path.segments.len() - 1).collect();
     let mut last = GenericArgs::empty();
-    last.bindings.push((name![Output], orig));
+    last.bindings.push(AssociatedTypeBinding {
+        name: name![Output],
+        type_ref: Some(orig),
+        bounds: Vec::new(),
+    });
     generic_args.push(Some(Arc::new(last)));
 
     Path::from_known_path(path, generic_args)
diff --git a/crates/ra_hir_def/src/path.rs b/crates/ra_hir_def/src/path.rs
index 91c7b3e09..162b3c8c7 100644
--- a/crates/ra_hir_def/src/path.rs
+++ b/crates/ra_hir_def/src/path.rs
@@ -14,7 +14,10 @@ use hir_expand::{
 use ra_db::CrateId;
 use ra_syntax::ast;
 
-use crate::{type_ref::TypeRef, InFile};
+use crate::{
+    type_ref::{TypeBound, TypeRef},
+    InFile,
+};
 
 #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct ModPath {
@@ -111,7 +114,21 @@ pub struct GenericArgs {
     /// is left out.
     pub has_self_type: bool,
     /// Associated type bindings like in `Iterator<Item = T>`.
-    pub bindings: Vec<(Name, TypeRef)>,
+    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.
diff --git a/crates/ra_hir_def/src/path/lower.rs b/crates/ra_hir_def/src/path/lower.rs
index 0f806d6fb..9ec2e0dcd 100644
--- a/crates/ra_hir_def/src/path/lower.rs
+++ b/crates/ra_hir_def/src/path/lower.rs
@@ -9,11 +9,12 @@ use hir_expand::{
     hygiene::Hygiene,
     name::{name, AsName},
 };
-use ra_syntax::ast::{self, AstNode, TypeAscriptionOwner};
+use ra_syntax::ast::{self, AstNode, TypeAscriptionOwner, TypeBoundsOwner};
 
+use super::AssociatedTypeBinding;
 use crate::{
     path::{GenericArg, GenericArgs, ModPath, Path, PathKind},
-    type_ref::TypeRef,
+    type_ref::{TypeBound, TypeRef},
 };
 
 pub(super) use lower_use::lower_use_tree;
@@ -136,10 +137,16 @@ pub(super) fn lower_generic_args(node: ast::TypeArgList) -> Option<GenericArgs>
     // lifetimes ignored for now
     let mut bindings = Vec::new();
     for assoc_type_arg in node.assoc_type_args() {
+        let assoc_type_arg: ast::AssocTypeArg = assoc_type_arg;
         if let Some(name_ref) = assoc_type_arg.name_ref() {
             let name = name_ref.as_name();
-            let type_ref = TypeRef::from_ast_opt(assoc_type_arg.type_ref());
-            bindings.push((name, type_ref));
+            let type_ref = assoc_type_arg.type_ref().map(TypeRef::from_ast);
+            let bounds = if let Some(l) = assoc_type_arg.type_bound_list() {
+                l.bounds().map(TypeBound::from_ast).collect()
+            } else {
+                Vec::new()
+            };
+            bindings.push(AssociatedTypeBinding { name, type_ref, bounds });
         }
     }
     if args.is_empty() && bindings.is_empty() {
@@ -168,7 +175,11 @@ fn lower_generic_args_from_fn_path(
     }
     if let Some(ret_type) = ret_type {
         let type_ref = TypeRef::from_ast_opt(ret_type.type_ref());
-        bindings.push((name![Output], type_ref))
+        bindings.push(AssociatedTypeBinding {
+            name: name![Output],
+            type_ref: Some(type_ref),
+            bounds: Vec::new(),
+        });
     }
     if args.is_empty() && bindings.is_empty() {
         None
diff --git a/crates/ra_hir_def/src/type_ref.rs b/crates/ra_hir_def/src/type_ref.rs
index ea29c4176..f308c6bdf 100644
--- a/crates/ra_hir_def/src/type_ref.rs
+++ b/crates/ra_hir_def/src/type_ref.rs
@@ -163,8 +163,16 @@ impl TypeRef {
                         let crate::path::GenericArg::Type(type_ref) = arg;
                         go(type_ref, f);
                     }
-                    for (_, type_ref) in &args_and_bindings.bindings {
-                        go(type_ref, f);
+                    for binding in &args_and_bindings.bindings {
+                        if let Some(type_ref) = &binding.type_ref {
+                            go(type_ref, f);
+                        }
+                        for bound in &binding.bounds {
+                            match bound {
+                                TypeBound::Path(path) => go_path(path, f),
+                                TypeBound::Error => (),
+                            }
+                        }
                     }
                 }
             }