13 files changed, 735 insertions, 120 deletions

diff --git a/crates/ra_hir_ty/src/_match.rs b/crates/ra_hir_ty/src/_match.rs
index 9e9a9d047..a64be9848 100644
--- a/crates/ra_hir_ty/src/_match.rs
+++ b/crates/ra_hir_ty/src/_match.rs
@@ -289,7 +289,7 @@ impl PatStack {
         Self::from_slice(&self.0[1..])
     }
 
-    fn replace_head_with(&self, pat_ids: &[PatId]) -> PatStack {
+    fn replace_head_with<T: Into<PatIdOrWild> + Copy>(&self, pat_ids: &[T]) -> PatStack {
         let mut patterns: PatStackInner = smallvec![];
         for pat in pat_ids {
             patterns.push((*pat).into());
@@ -320,12 +320,14 @@ impl PatStack {
         constructor: &Constructor,
     ) -> MatchCheckResult<Option<PatStack>> {
         let result = match (self.head().as_pat(cx), constructor) {
-            (Pat::Tuple(ref pat_ids), Constructor::Tuple { arity }) => {
-                debug_assert_eq!(
-                    pat_ids.len(),
-                    *arity,
-                    "we type check before calling this code, so we should never hit this case",
-                );
+            (Pat::Tuple { args: ref pat_ids, ellipsis }, Constructor::Tuple { arity: _ }) => {
+                if ellipsis.is_some() {
+                    // If there are ellipsis here, we should add the correct number of
+                    // Pat::Wild patterns to `pat_ids`. We should be able to use the
+                    // constructors arity for this, but at the time of writing we aren't
+                    // correctly calculating this arity when ellipsis are present.
+                    return Err(MatchCheckErr::NotImplemented);
+                }
 
                 Some(self.replace_head_with(pat_ids))
             }
@@ -351,19 +353,47 @@ impl PatStack {
                     Some(self.to_tail())
                 }
             }
-            (Pat::TupleStruct { args: ref pat_ids, .. }, Constructor::Enum(enum_constructor)) => {
+            (
+                Pat::TupleStruct { args: ref pat_ids, ellipsis, .. },
+                Constructor::Enum(enum_constructor),
+            ) => {
                 let pat_id = self.head().as_id().expect("we know this isn't a wild");
                 if !enum_variant_matches(cx, pat_id, *enum_constructor) {
                     None
                 } else {
-                    // If the enum variant matches, then we need to confirm
-                    // that the number of patterns aligns with the expected
-                    // number of patterns for that enum variant.
-                    if pat_ids.len() != constructor.arity(cx)? {
-                        return Err(MatchCheckErr::MalformedMatchArm);
+                    let constructor_arity = constructor.arity(cx)?;
+                    if let Some(ellipsis_position) = ellipsis {
+                        // If there are ellipsis in the pattern, the ellipsis must take the place
+                        // of at least one sub-pattern, so `pat_ids` should be smaller than the
+                        // constructor arity.
+                        if pat_ids.len() < constructor_arity {
+                            let mut new_patterns: Vec<PatIdOrWild> = vec![];
+
+                            for pat_id in &pat_ids[0..ellipsis_position] {
+                                new_patterns.push((*pat_id).into());
+                            }
+
+                            for _ in 0..(constructor_arity - pat_ids.len()) {
+                                new_patterns.push(PatIdOrWild::Wild);
+                            }
+
+                            for pat_id in &pat_ids[ellipsis_position..pat_ids.len()] {
+                                new_patterns.push((*pat_id).into());
+                            }
+
+                            Some(self.replace_head_with(&new_patterns))
+                        } else {
+                            return Err(MatchCheckErr::MalformedMatchArm);
+                        }
+                    } else {
+                        // If there is no ellipsis in the tuple pattern, the number
+                        // of patterns must equal the constructor arity.
+                        if pat_ids.len() == constructor_arity {
+                            Some(self.replace_head_with(pat_ids))
+                        } else {
+                            return Err(MatchCheckErr::MalformedMatchArm);
+                        }
                     }
-
-                    Some(self.replace_head_with(pat_ids))
                 }
             }
             (Pat::Or(_), _) => return Err(MatchCheckErr::NotImplemented),
@@ -644,7 +674,11 @@ impl Constructor {
 fn pat_constructor(cx: &MatchCheckCtx, pat: PatIdOrWild) -> MatchCheckResult<Option<Constructor>> {
     let res = match pat.as_pat(cx) {
         Pat::Wild => None,
-        Pat::Tuple(pats) => Some(Constructor::Tuple { arity: pats.len() }),
+        // FIXME somehow create the Tuple constructor with the proper arity. If there are
+        // ellipsis, the arity is not equal to the number of patterns.
+        Pat::Tuple { args: pats, ellipsis } if ellipsis.is_none() => {
+            Some(Constructor::Tuple { arity: pats.len() })
+        }
         Pat::Lit(lit_expr) => match cx.body.exprs[lit_expr] {
             Expr::Literal(Literal::Bool(val)) => Some(Constructor::Bool(val)),
             _ => return Err(MatchCheckErr::NotImplemented),
@@ -973,6 +1007,47 @@ mod tests {
     }
 
     #[test]
+    fn tuple_of_bools_with_ellipsis_at_end_no_diagnostic() {
+        let content = r"
+            fn test_fn() {
+                match (false, true, false) {
+                    (false, ..) => {},
+                    (true, ..) => {},
+                }
+            }
+        ";
+
+        check_no_diagnostic(content);
+    }
+
+    #[test]
+    fn tuple_of_bools_with_ellipsis_at_beginning_no_diagnostic() {
+        let content = r"
+            fn test_fn() {
+                match (false, true, false) {
+                    (.., false) => {},
+                    (.., true) => {},
+                }
+            }
+        ";
+
+        check_no_diagnostic(content);
+    }
+
+    #[test]
+    fn tuple_of_bools_with_ellipsis_no_diagnostic() {
+        let content = r"
+            fn test_fn() {
+                match (false, true, false) {
+                    (..) => {},
+                }
+            }
+        ";
+
+        check_no_diagnostic(content);
+    }
+
+    #[test]
     fn tuple_of_tuple_and_bools_no_arms() {
         let content = r"
             fn test_fn() {
@@ -1315,8 +1390,9 @@ mod tests {
             }
         ";
 
-        // Match arms with the incorrect type are filtered out.
-        check_diagnostic(content);
+        // Match statements with arms that don't match the
+        // expression pattern do not fire this diagnostic.
+        check_no_diagnostic(content);
     }
 
     #[test]
@@ -1330,8 +1406,9 @@ mod tests {
             }
         ";
 
-        // Match arms with the incorrect type are filtered out.
-        check_diagnostic(content);
+        // Match statements with arms that don't match the
+        // expression pattern do not fire this diagnostic.
+        check_no_diagnostic(content);
     }
 
     #[test]
@@ -1344,8 +1421,9 @@ mod tests {
             }
         ";
 
-        // Match arms with the incorrect type are filtered out.
-        check_diagnostic(content);
+        // Match statements with arms that don't match the
+        // expression pattern do not fire this diagnostic.
+        check_no_diagnostic(content);
     }
 
     #[test]
@@ -1383,6 +1461,163 @@ mod tests {
         // we don't create a diagnostic).
         check_no_diagnostic(content);
     }
+
+    #[test]
+    fn expr_diverges() {
+        let content = r"
+            enum Either {
+                A,
+                B,
+            }
+            fn test_fn() {
+                match loop {} {
+                    Either::A => (),
+                    Either::B => (),
+                }
+            }
+        ";
+
+        check_no_diagnostic(content);
+    }
+
+    #[test]
+    fn expr_loop_with_break() {
+        let content = r"
+            enum Either {
+                A,
+                B,
+            }
+            fn test_fn() {
+                match loop { break Foo::A } {
+                    Either::A => (),
+                    Either::B => (),
+                }
+            }
+        ";
+
+        check_no_diagnostic(content);
+    }
+
+    #[test]
+    fn expr_partially_diverges() {
+        let content = r"
+            enum Either<T> {
+                A(T),
+                B,
+            }
+            fn foo() -> Either<!> {
+                Either::B
+            }
+            fn test_fn() -> u32 {
+                match foo() {
+                    Either::A(val) => val,
+                    Either::B => 0,
+                }
+            }
+        ";
+
+        check_no_diagnostic(content);
+    }
+
+    #[test]
+    fn enum_tuple_partial_ellipsis_no_diagnostic() {
+        let content = r"
+            enum Either {
+                A(bool, bool, bool, bool),
+                B,
+            }
+            fn test_fn() {
+                match Either::B {
+                    Either::A(true, .., true) => {},
+                    Either::A(true, .., false) => {},
+                    Either::A(false, .., true) => {},
+                    Either::A(false, .., false) => {},
+                    Either::B => {},
+                }
+            }
+        ";
+
+        check_no_diagnostic(content);
+    }
+
+    #[test]
+    fn enum_tuple_partial_ellipsis_2_no_diagnostic() {
+        let content = r"
+            enum Either {
+                A(bool, bool, bool, bool),
+                B,
+            }
+            fn test_fn() {
+                match Either::B {
+                    Either::A(true, .., true) => {},
+                    Either::A(true, .., false) => {},
+                    Either::A(.., true) => {},
+                    Either::A(.., false) => {},
+                    Either::B => {},
+                }
+            }
+        ";
+
+        check_no_diagnostic(content);
+    }
+
+    #[test]
+    fn enum_tuple_partial_ellipsis_missing_arm() {
+        let content = r"
+            enum Either {
+                A(bool, bool, bool, bool),
+                B,
+            }
+            fn test_fn() {
+                match Either::B {
+                    Either::A(true, .., true) => {},
+                    Either::A(true, .., false) => {},
+                    Either::A(false, .., false) => {},
+                    Either::B => {},
+                }
+            }
+        ";
+
+        check_diagnostic(content);
+    }
+
+    #[test]
+    fn enum_tuple_partial_ellipsis_2_missing_arm() {
+        let content = r"
+            enum Either {
+                A(bool, bool, bool, bool),
+                B,
+            }
+            fn test_fn() {
+                match Either::B {
+                    Either::A(true, .., true) => {},
+                    Either::A(true, .., false) => {},
+                    Either::A(.., true) => {},
+                    Either::B => {},
+                }
+            }
+        ";
+
+        check_diagnostic(content);
+    }
+
+    #[test]
+    fn enum_tuple_ellipsis_no_diagnostic() {
+        let content = r"
+            enum Either {
+                A(bool, bool, bool, bool),
+                B,
+            }
+            fn test_fn() {
+                match Either::B {
+                    Either::A(..) => {},
+                    Either::B => {},
+                }
+            }
+        ";
+
+        check_no_diagnostic(content);
+    }
 }
 
 #[cfg(test)]
@@ -1452,4 +1687,75 @@ mod false_negatives {
         // We do not currently handle patterns with internal `or`s.
         check_no_diagnostic(content);
     }
+
+    #[test]
+    fn expr_diverges_missing_arm() {
+        let content = r"
+            enum Either {
+                A,
+                B,
+            }
+            fn test_fn() {
+                match loop {} {
+                    Either::A => (),
+                }
+            }
+        ";
+
+        // This is a false negative.
+        // Even though the match expression diverges, rustc fails
+        // to compile here since `Either::B` is missing.
+        check_no_diagnostic(content);
+    }
+
+    #[test]
+    fn expr_loop_missing_arm() {
+        let content = r"
+            enum Either {
+                A,
+                B,
+            }
+            fn test_fn() {
+                match loop { break Foo::A } {
+                    Either::A => (),
+                }
+            }
+        ";
+
+        // This is a false negative.
+        // We currently infer the type of `loop { break Foo::A }` to `!`, which
+        // causes us to skip the diagnostic since `Either::A` doesn't type check
+        // with `!`.
+        check_no_diagnostic(content);
+    }
+
+    #[test]
+    fn tuple_of_bools_with_ellipsis_at_end_missing_arm() {
+        let content = r"
+            fn test_fn() {
+                match (false, true, false) {
+                    (false, ..) => {},
+                }
+            }
+        ";
+
+        // This is a false negative.
+        // We don't currently handle tuple patterns with ellipsis.
+        check_no_diagnostic(content);
+    }
+
+    #[test]
+    fn tuple_of_bools_with_ellipsis_at_beginning_missing_arm() {
+        let content = r"
+            fn test_fn() {
+                match (false, true, false) {
+                    (.., false) => {},
+                }
+            }
+        ";
+
+        // This is a false negative.
+        // We don't currently handle tuple patterns with ellipsis.
+        check_no_diagnostic(content);
+    }
 }
diff --git a/crates/ra_hir_ty/src/db.rs b/crates/ra_hir_ty/src/db.rs
index 1462b053f..33da16b48 100644
--- a/crates/ra_hir_ty/src/db.rs
+++ b/crates/ra_hir_ty/src/db.rs
@@ -11,7 +11,7 @@ use ra_db::{impl_intern_key, salsa, CrateId, Upcast};
 use ra_prof::profile;
 
 use crate::{
-    method_resolution::CrateImplDefs,
+    method_resolution::{CrateImplDefs, TyFingerprint},
     traits::{chalk, AssocTyValue, Impl},
     Binders, CallableDef, GenericPredicate, InferenceResult, PolyFnSig, Substs, TraitRef, Ty,
     TyDefId, TypeCtor, ValueTyDefId,
@@ -65,7 +65,12 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
     fn impls_in_crate(&self, krate: CrateId) -> Arc<CrateImplDefs>;
 
     #[salsa::invoke(crate::traits::impls_for_trait_query)]
-    fn impls_for_trait(&self, krate: CrateId, trait_: TraitId) -> Arc<[ImplId]>;
+    fn impls_for_trait(
+        &self,
+        krate: CrateId,
+        trait_: TraitId,
+        self_ty_fp: Option<TyFingerprint>,
+    ) -> Arc<[ImplId]>;
 
     // Interned IDs for Chalk integration
     #[salsa::interned]
diff --git a/crates/ra_hir_ty/src/expr.rs b/crates/ra_hir_ty/src/expr.rs
index 827b687de..21abbcf1e 100644
--- a/crates/ra_hir_ty/src/expr.rs
+++ b/crates/ra_hir_ty/src/expr.rs
@@ -89,21 +89,19 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         let (_, source_map) = db.body_with_source_map(self.func.into());
 
         if let Ok(source_ptr) = source_map.expr_syntax(id) {
-            if let Some(expr) = source_ptr.value.as_ref().left() {
-                let root = source_ptr.file_syntax(db.upcast());
-                if let ast::Expr::RecordLit(record_lit) = expr.to_node(&root) {
-                    if let Some(field_list) = record_lit.record_field_list() {
-                        let variant_data = variant_data(db.upcast(), variant_def);
-                        let missed_fields = missed_fields
-                            .into_iter()
-                            .map(|idx| variant_data.fields()[idx].name.clone())
-                            .collect();
-                        self.sink.push(MissingFields {
-                            file: source_ptr.file_id,
-                            field_list: AstPtr::new(&field_list),
-                            missed_fields,
-                        })
-                    }
+            let root = source_ptr.file_syntax(db.upcast());
+            if let ast::Expr::RecordLit(record_lit) = &source_ptr.value.to_node(&root) {
+                if let Some(field_list) = record_lit.record_field_list() {
+                    let variant_data = variant_data(db.upcast(), variant_def);
+                    let missed_fields = missed_fields
+                        .into_iter()
+                        .map(|idx| variant_data.fields()[idx].name.clone())
+                        .collect();
+                    self.sink.push(MissingFields {
+                        file: source_ptr.file_id,
+                        field_list: AstPtr::new(&field_list),
+                        missed_fields,
+                    })
                 }
             }
         }
@@ -163,12 +161,6 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
 
         let mut seen = Matrix::empty();
         for pat in pats {
-            // We skip any patterns whose type we cannot resolve.
-            //
-            // This could lead to false positives in this diagnostic, so
-            // it might be better to skip the entire diagnostic if we either
-            // cannot resolve a match arm or determine that the match arm has
-            // the wrong type.
             if let Some(pat_ty) = infer.type_of_pat.get(pat) {
                 // We only include patterns whose type matches the type
                 // of the match expression. If we had a InvalidMatchArmPattern
@@ -191,8 +183,15 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
                     // to the matrix here.
                     let v = PatStack::from_pattern(pat);
                     seen.push(&cx, v);
+                    continue;
                 }
             }
+
+            // If we can't resolve the type of a pattern, or the pattern type doesn't
+            // fit the match expression, we skip this diagnostic. Skipping the entire
+            // diagnostic rather than just not including this match arm is preferred
+            // to avoid the chance of false positives.
+            return;
         }
 
         match is_useful(&cx, &seen, &PatStack::from_wild()) {
@@ -205,18 +204,16 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         }
 
         if let Ok(source_ptr) = source_map.expr_syntax(id) {
-            if let Some(expr) = source_ptr.value.as_ref().left() {
-                let root = source_ptr.file_syntax(db.upcast());
-                if let ast::Expr::MatchExpr(match_expr) = expr.to_node(&root) {
-                    if let (Some(match_expr), Some(arms)) =
-                        (match_expr.expr(), match_expr.match_arm_list())
-                    {
-                        self.sink.push(MissingMatchArms {
-                            file: source_ptr.file_id,
-                            match_expr: AstPtr::new(&match_expr),
-                            arms: AstPtr::new(&arms),
-                        })
-                    }
+            let root = source_ptr.file_syntax(db.upcast());
+            if let ast::Expr::MatchExpr(match_expr) = &source_ptr.value.to_node(&root) {
+                if let (Some(match_expr), Some(arms)) =
+                    (match_expr.expr(), match_expr.match_arm_list())
+                {
+                    self.sink.push(MissingMatchArms {
+                        file: source_ptr.file_id,
+                        match_expr: AstPtr::new(&match_expr),
+                        arms: AstPtr::new(&arms),
+                    })
                 }
             }
         }
@@ -247,9 +244,8 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
             let (_, source_map) = db.body_with_source_map(self.func.into());
 
             if let Ok(source_ptr) = source_map.expr_syntax(id) {
-                if let Some(expr) = source_ptr.value.left() {
-                    self.sink.push(MissingOkInTailExpr { file: source_ptr.file_id, expr });
-                }
+                self.sink
+                    .push(MissingOkInTailExpr { file: source_ptr.file_id, expr: source_ptr.value });
             }
         }
     }
diff --git a/crates/ra_hir_ty/src/infer/pat.rs b/crates/ra_hir_ty/src/infer/pat.rs
index 078476f76..8ec4d4ace 100644
--- a/crates/ra_hir_ty/src/infer/pat.rs
+++ b/crates/ra_hir_ty/src/infer/pat.rs
@@ -85,7 +85,7 @@ impl<'a> InferenceContext<'a> {
         let body = Arc::clone(&self.body); // avoid borrow checker problem
 
         let is_non_ref_pat = match &body[pat] {
-            Pat::Tuple(..)
+            Pat::Tuple { .. }
             | Pat::Or(..)
             | Pat::TupleStruct { .. }
             | Pat::Record { .. }
@@ -116,7 +116,7 @@ impl<'a> InferenceContext<'a> {
         let expected = expected;
 
         let ty = match &body[pat] {
-            Pat::Tuple(ref args) => {
+            Pat::Tuple { ref args, .. } => {
                 let expectations = match expected.as_tuple() {
                     Some(parameters) => &*parameters.0,
                     _ => &[],
@@ -155,7 +155,7 @@ impl<'a> InferenceContext<'a> {
                 let subty = self.infer_pat(*pat, expectation, default_bm);
                 Ty::apply_one(TypeCtor::Ref(*mutability), subty)
             }
-            Pat::TupleStruct { path: p, args: subpats } => {
+            Pat::TupleStruct { path: p, args: subpats, .. } => {
                 self.infer_tuple_struct_pat(p.as_ref(), subpats, expected, default_bm, pat)
             }
             Pat::Record { path: p, args: fields, ellipsis: _ } => {
diff --git a/crates/ra_hir_ty/src/lower.rs b/crates/ra_hir_ty/src/lower.rs
index 6c7bbc448..cc1ac8e3e 100644
--- a/crates/ra_hir_ty/src/lower.rs
+++ b/crates/ra_hir_ty/src/lower.rs
@@ -8,6 +8,8 @@
 use std::iter;
 use std::sync::Arc;
 
+use smallvec::SmallVec;
+
 use hir_def::{
     adt::StructKind,
     builtin_type::BuiltinType,
@@ -360,13 +362,23 @@ impl Ty {
             },
             Some(TypeNs::GenericParam(param_id)) => {
                 let predicates = ctx.db.generic_predicates_for_param(param_id);
-                predicates
+                let mut traits_: Vec<_> = predicates
                     .iter()
                     .filter_map(|pred| match &pred.value {
                         GenericPredicate::Implemented(tr) => Some(tr.trait_),
                         _ => None,
                     })
-                    .collect()
+                    .collect();
+                // Handle `Self::Type` referring to own associated type in trait definitions
+                if let GenericDefId::TraitId(trait_id) = param_id.parent {
+                    let generics = generics(ctx.db.upcast(), trait_id.into());
+                    if generics.params.types[param_id.local_id].provenance
+                        == TypeParamProvenance::TraitSelf
+                    {
+                        traits_.push(trait_id);
+                    }
+                }
+                traits_
             }
             _ => return Ty::Unknown,
         };
@@ -596,21 +608,35 @@ fn assoc_type_bindings_from_type_bound<'a>(
         .into_iter()
         .flat_map(|segment| segment.args_and_bindings.into_iter())
         .flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
-        .map(move |(name, type_ref)| {
+        .flat_map(move |binding| {
             let associated_ty = associated_type_by_name_including_super_traits(
                 ctx.db.upcast(),
                 trait_ref.trait_,
-                &name,
+                &binding.name,
             );
             let associated_ty = match associated_ty {
-                None => return GenericPredicate::Error,
+                None => return SmallVec::<[GenericPredicate; 1]>::new(),
                 Some(t) => t,
             };
             let projection_ty =
                 ProjectionTy { associated_ty, parameters: trait_ref.substs.clone() };
-            let ty = Ty::from_hir(ctx, type_ref);
-            let projection_predicate = ProjectionPredicate { projection_ty, ty };
-            GenericPredicate::Projection(projection_predicate)
+            let mut preds = SmallVec::with_capacity(
+                binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
+            );
+            if let Some(type_ref) = &binding.type_ref {
+                let ty = Ty::from_hir(ctx, type_ref);
+                let projection_predicate =
+                    ProjectionPredicate { projection_ty: projection_ty.clone(), ty };
+                preds.push(GenericPredicate::Projection(projection_predicate));
+            }
+            for bound in &binding.bounds {
+                preds.extend(GenericPredicate::from_type_bound(
+                    ctx,
+                    bound,
+                    Ty::Projection(projection_ty.clone()),
+                ));
+            }
+            preds
         })
 }
 
diff --git a/crates/ra_hir_ty/src/method_resolution.rs b/crates/ra_hir_ty/src/method_resolution.rs
index 74a0bc7db..657284fd0 100644
--- a/crates/ra_hir_ty/src/method_resolution.rs
+++ b/crates/ra_hir_ty/src/method_resolution.rs
@@ -34,7 +34,7 @@ impl TyFingerprint {
     /// Creates a TyFingerprint for looking up an impl. Only certain types can
     /// have impls: if we have some `struct S`, we can have an `impl S`, but not
     /// `impl &S`. Hence, this will return `None` for reference types and such.
-    fn for_impl(ty: &Ty) -> Option<TyFingerprint> {
+    pub(crate) fn for_impl(ty: &Ty) -> Option<TyFingerprint> {
         match ty {
             Ty::Apply(a_ty) => Some(TyFingerprint::Apply(a_ty.ctor)),
             _ => None,
@@ -45,7 +45,7 @@ impl TyFingerprint {
 #[derive(Debug, PartialEq, Eq)]
 pub struct CrateImplDefs {
     impls: FxHashMap<TyFingerprint, Vec<ImplId>>,
-    impls_by_trait: FxHashMap<TraitId, Vec<ImplId>>,
+    impls_by_trait: FxHashMap<TraitId, FxHashMap<Option<TyFingerprint>, Vec<ImplId>>>,
 }
 
 impl CrateImplDefs {
@@ -59,7 +59,14 @@ impl CrateImplDefs {
             for impl_id in module_data.scope.impls() {
                 match db.impl_trait(impl_id) {
                     Some(tr) => {
-                        res.impls_by_trait.entry(tr.value.trait_).or_default().push(impl_id);
+                        let self_ty = db.impl_self_ty(impl_id);
+                        let self_ty_fp = TyFingerprint::for_impl(&self_ty.value);
+                        res.impls_by_trait
+                            .entry(tr.value.trait_)
+                            .or_default()
+                            .entry(self_ty_fp)
+                            .or_default()
+                            .push(impl_id);
                     }
                     None => {
                         let self_ty = db.impl_self_ty(impl_id);
@@ -79,11 +86,39 @@ impl CrateImplDefs {
     }
 
     pub fn lookup_impl_defs_for_trait(&self, tr: TraitId) -> impl Iterator<Item = ImplId> + '_ {
-        self.impls_by_trait.get(&tr).into_iter().flatten().copied()
+        self.impls_by_trait
+            .get(&tr)
+            .into_iter()
+            .flat_map(|m| m.values().flat_map(|v| v.iter().copied()))
+    }
+
+    pub fn lookup_impl_defs_for_trait_and_ty(
+        &self,
+        tr: TraitId,
+        fp: TyFingerprint,
+    ) -> impl Iterator<Item = ImplId> + '_ {
+        self.impls_by_trait
+            .get(&tr)
+            .and_then(|m| m.get(&Some(fp)))
+            .into_iter()
+            .flatten()
+            .copied()
+            .chain(
+                self.impls_by_trait
+                    .get(&tr)
+                    .and_then(|m| m.get(&None))
+                    .into_iter()
+                    .flatten()
+                    .copied(),
+            )
     }
 
     pub fn all_impls<'a>(&'a self) -> impl Iterator<Item = ImplId> + 'a {
-        self.impls.values().chain(self.impls_by_trait.values()).flatten().copied()
+        self.impls
+            .values()
+            .chain(self.impls_by_trait.values().flat_map(|m| m.values()))
+            .flatten()
+            .copied()
     }
 }
 
diff --git a/crates/ra_hir_ty/src/tests.rs b/crates/ra_hir_ty/src/tests.rs
index 54e31602f..81fc0f63a 100644
--- a/crates/ra_hir_ty/src/tests.rs
+++ b/crates/ra_hir_ty/src/tests.rs
@@ -82,9 +82,7 @@ fn infer_with_mismatches(content: &str, include_mismatches: bool) -> String {
 
         for (expr, ty) in inference_result.type_of_expr.iter() {
             let syntax_ptr = match body_source_map.expr_syntax(expr) {
-                Ok(sp) => {
-                    sp.map(|ast| ast.either(|it| it.syntax_node_ptr(), |it| it.syntax_node_ptr()))
-                }
+                Ok(sp) => sp.map(|ast| ast.syntax_node_ptr()),
                 Err(SyntheticSyntax) => continue,
             };
             types.push((syntax_ptr.clone(), ty));
diff --git a/crates/ra_hir_ty/src/tests/patterns.rs b/crates/ra_hir_ty/src/tests/patterns.rs
index 6e5d2247c..07cbc521a 100644
--- a/crates/ra_hir_ty/src/tests/patterns.rs
+++ b/crates/ra_hir_ty/src/tests/patterns.rs
@@ -1,7 +1,8 @@
-use super::{infer, infer_with_mismatches};
 use insta::assert_snapshot;
 use test_utils::covers;
 
+use super::{infer, infer_with_mismatches};
+
 #[test]
 fn infer_pattern() {
     assert_snapshot!(
diff --git a/crates/ra_hir_ty/src/tests/regression.rs b/crates/ra_hir_ty/src/tests/regression.rs
index 3402e0cb5..d69115a2f 100644
--- a/crates/ra_hir_ty/src/tests/regression.rs
+++ b/crates/ra_hir_ty/src/tests/regression.rs
@@ -451,8 +451,7 @@ pub mod str {
 "#,
     );
 
-    // should be Option<char>, but currently not because of Chalk ambiguity problem
-    assert_eq!("(Option<{unknown}>, Option<{unknown}>)", super::type_at_pos(&db, pos));
+    assert_eq!("(Option<char>, Option<char>)", super::type_at_pos(&db, pos));
 }
 
 #[test]
diff --git a/crates/ra_hir_ty/src/tests/traits.rs b/crates/ra_hir_ty/src/tests/traits.rs
index 22ae6ca90..b3a2fc439 100644
--- a/crates/ra_hir_ty/src/tests/traits.rs
+++ b/crates/ra_hir_ty/src/tests/traits.rs
@@ -1803,7 +1803,7 @@ fn test<T, U>() where T::Item: Trait2, T: Trait<U::Item>, U: Trait<()> {
 }
 
 #[test]
-fn unselected_projection_on_trait_self() {
+fn unselected_projection_on_impl_self() {
     assert_snapshot!(infer(
         r#"
 //- /main.rs
@@ -1844,6 +1844,30 @@ impl Trait for S2 {
 }
 
 #[test]
+fn unselected_projection_on_trait_self() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Trait {
+    type Item;
+
+    fn f(&self) -> Self::Item { loop {} }
+}
+
+struct S;
+impl Trait for S {
+    type Item = u32;
+}
+
+fn test() {
+    S.f()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "u32");
+}
+
+#[test]
 fn trait_impl_self_ty() {
     let t = type_at(
         r#"
@@ -1924,6 +1948,53 @@ fn test<T, U>() where T: Trait<U::Item>, U: Trait<T::Item> {
 }
 
 #[test]
+fn inline_assoc_type_bounds_1() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Iterator {
+    type Item;
+}
+trait OtherTrait<T> {
+    fn foo(&self) -> T;
+}
+
+// workaround for Chalk assoc type normalization problems
+pub struct S<T>;
+impl<T: Iterator> Iterator for S<T> {
+    type Item = <T as Iterator>::Item;
+}
+
+fn test<I: Iterator<Item: OtherTrait<u32>>>() {
+    let x: <S<I> as Iterator>::Item;
+    x.foo()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "u32");
+}
+
+#[test]
+fn inline_assoc_type_bounds_2() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Iterator {
+    type Item;
+}
+
+fn test<I: Iterator<Item: Iterator<Item = u32>>>() {
+    let x: <<I as Iterator>::Item as Iterator>::Item;
+    x<|>;
+}
+"#,
+    );
+    // assert_eq!(t, "u32");
+    // doesn't currently work, Chalk #234
+    assert_eq!(t, "{unknown}");
+}
+
+#[test]
 fn unify_impl_trait() {
     assert_snapshot!(
         infer_with_mismatches(r#"
@@ -2023,6 +2094,33 @@ fn main() {
 }
 
 #[test]
+fn associated_type_bound() {
+    let t = type_at(
+        r#"
+//- /main.rs
+pub trait Trait {
+    type Item: OtherTrait<u32>;
+}
+pub trait OtherTrait<T> {
+    fn foo(&self) -> T;
+}
+
+// this is just a workaround for chalk#234
+pub struct S<T>;
+impl<T: Trait> Trait for S<T> {
+    type Item = <T as Trait>::Item;
+}
+
+fn test<T: Trait>() {
+    let y: <S<T> as Trait>::Item = no_matter;
+    y.foo()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "u32");
+}
+
+#[test]
 fn dyn_trait_through_chalk() {
     let t = type_at(
         r#"
diff --git a/crates/ra_hir_ty/src/traits.rs b/crates/ra_hir_ty/src/traits.rs
index 21e233379..44fbdb197 100644
--- a/crates/ra_hir_ty/src/traits.rs
+++ b/crates/ra_hir_ty/src/traits.rs
@@ -7,7 +7,7 @@ use ra_db::{impl_intern_key, salsa, CrateId};
 use ra_prof::profile;
 use rustc_hash::FxHashSet;
 
-use crate::{db::HirDatabase, DebruijnIndex};
+use crate::{db::HirDatabase, method_resolution::TyFingerprint, DebruijnIndex};
 
 use super::{Canonical, GenericPredicate, HirDisplay, ProjectionTy, TraitRef, Ty, TypeWalk};
 
@@ -40,7 +40,12 @@ pub(crate) fn impls_for_trait_query(
     db: &dyn HirDatabase,
     krate: CrateId,
     trait_: TraitId,
+    self_ty_fp: Option<TyFingerprint>,
 ) -> Arc<[ImplId]> {
+    // FIXME: We could be a lot smarter here - because of the orphan rules and
+    // the fact that the trait and the self type need to be in the dependency
+    // tree of a crate somewhere for an impl to exist, we could skip looking in
+    // a lot of crates completely
     let mut impls = FxHashSet::default();
     // We call the query recursively here. On the one hand, this means we can
     // reuse results from queries for different crates; on the other hand, this
@@ -48,10 +53,13 @@ pub(crate) fn impls_for_trait_query(
     // ones the user is editing), so this may actually be a waste of memory. I'm
     // doing it like this mainly for simplicity for now.
     for dep in &db.crate_graph()[krate].dependencies {
-        impls.extend(db.impls_for_trait(dep.crate_id, trait_).iter());
+        impls.extend(db.impls_for_trait(dep.crate_id, trait_, self_ty_fp).iter());
     }
     let crate_impl_defs = db.impls_in_crate(krate);
-    impls.extend(crate_impl_defs.lookup_impl_defs_for_trait(trait_));
+    match self_ty_fp {
+        Some(fp) => impls.extend(crate_impl_defs.lookup_impl_defs_for_trait_and_ty(trait_, fp)),
+        None => impls.extend(crate_impl_defs.lookup_impl_defs_for_trait(trait_)),
+    }
     impls.into_iter().collect()
 }
 
@@ -186,13 +194,16 @@ fn solve(
         }
         remaining > 0
     };
-    let mut solve = || solver.solve_limited(&context, goal, should_continue);
+    let mut solve = || {
+        let solution = solver.solve_limited(&context, goal, should_continue);
+        log::debug!("solve({:?}) => {:?}", goal, solution);
+        solution
+    };
     // don't set the TLS for Chalk unless Chalk debugging is active, to make
     // extra sure we only use it for debugging
     let solution =
         if is_chalk_debug() { chalk::tls::set_current_program(db, solve) } else { solve() };
 
-    log::debug!("solve({:?}) => {:?}", goal, solution);
     solution
 }
 
diff --git a/crates/ra_hir_ty/src/traits/chalk.rs b/crates/ra_hir_ty/src/traits/chalk.rs
index c5f1b5232..55eb0ffcb 100644
--- a/crates/ra_hir_ty/src/traits/chalk.rs
+++ b/crates/ra_hir_ty/src/traits/chalk.rs
@@ -16,8 +16,8 @@ use ra_db::{
 
 use super::{builtin, AssocTyValue, Canonical, ChalkContext, Impl, Obligation};
 use crate::{
-    db::HirDatabase, display::HirDisplay, utils::generics, ApplicationTy, GenericPredicate,
-    ProjectionTy, Substs, TraitRef, Ty, TypeCtor,
+    db::HirDatabase, display::HirDisplay, method_resolution::TyFingerprint, utils::generics,
+    ApplicationTy, GenericPredicate, ProjectionTy, Substs, TraitRef, Ty, TypeCtor,
 };
 
 pub(super) mod tls;
@@ -32,6 +32,9 @@ impl chalk_ir::interner::Interner for Interner {
     type InternedGoal = Arc<GoalData<Self>>;
     type InternedGoals = Vec<Goal<Self>>;
     type InternedSubstitution = Vec<Parameter<Self>>;
+    type InternedProgramClause = chalk_ir::ProgramClauseData<Self>;
+    type InternedProgramClauses = Vec<chalk_ir::ProgramClause<Self>>;
+    type InternedQuantifiedWhereClauses = Vec<chalk_ir::QuantifiedWhereClause<Self>>;
     type Identifier = TypeAliasId;
     type DefId = InternId;
 
@@ -181,6 +184,48 @@ impl chalk_ir::interner::Interner for Interner {
     ) -> &'a [Parameter<Self>] {
         substitution
     }
+
+    fn intern_program_clause(
+        &self,
+        data: chalk_ir::ProgramClauseData<Self>,
+    ) -> chalk_ir::ProgramClauseData<Self> {
+        data
+    }
+
+    fn program_clause_data<'a>(
+        &self,
+        clause: &'a chalk_ir::ProgramClauseData<Self>,
+    ) -> &'a chalk_ir::ProgramClauseData<Self> {
+        clause
+    }
+
+    fn intern_program_clauses(
+        &self,
+        data: impl IntoIterator<Item = chalk_ir::ProgramClause<Self>>,
+    ) -> Vec<chalk_ir::ProgramClause<Self>> {
+        data.into_iter().collect()
+    }
+
+    fn program_clauses_data<'a>(
+        &self,
+        clauses: &'a Vec<chalk_ir::ProgramClause<Self>>,
+    ) -> &'a [chalk_ir::ProgramClause<Self>] {
+        clauses
+    }
+
+    fn intern_quantified_where_clauses(
+        &self,
+        data: impl IntoIterator<Item = chalk_ir::QuantifiedWhereClause<Self>>,
+    ) -> Self::InternedQuantifiedWhereClauses {
+        data.into_iter().collect()
+    }
+
+    fn quantified_where_clauses_data<'a>(
+        &self,
+        clauses: &'a Self::InternedQuantifiedWhereClauses,
+    ) -> &'a [chalk_ir::QuantifiedWhereClause<Self>] {
+        clauses
+    }
 }
 
 impl chalk_ir::interner::HasInterner for Interner {
@@ -238,12 +283,10 @@ impl ToChalk for Ty {
             Ty::Bound(idx) => chalk_ir::TyData::BoundVar(idx).intern(&Interner),
             Ty::Infer(_infer_ty) => panic!("uncanonicalized infer ty"),
             Ty::Dyn(predicates) => {
-                let where_clauses = predicates
-                    .iter()
-                    .filter(|p| !p.is_error())
-                    .cloned()
-                    .map(|p| p.to_chalk(db))
-                    .collect();
+                let where_clauses = chalk_ir::QuantifiedWhereClauses::from(
+                    &Interner,
+                    predicates.iter().filter(|p| !p.is_error()).cloned().map(|p| p.to_chalk(db)),
+                );
                 let bounded_ty = chalk_ir::DynTy { bounds: make_binders(where_clauses, 1) };
                 chalk_ir::TyData::Dyn(bounded_ty).intern(&Interner)
             }
@@ -281,8 +324,12 @@ impl ToChalk for Ty {
             chalk_ir::TyData::InferenceVar(_iv) => Ty::Unknown,
             chalk_ir::TyData::Dyn(where_clauses) => {
                 assert_eq!(where_clauses.bounds.binders.len(), 1);
-                let predicates =
-                    where_clauses.bounds.value.into_iter().map(|c| from_chalk(db, c)).collect();
+                let predicates = where_clauses
+                    .bounds
+                    .skip_binders()
+                    .iter(&Interner)
+                    .map(|c| from_chalk(db, c.clone()))
+                    .collect();
                 Ty::Dyn(predicates)
             }
         }
@@ -426,7 +473,7 @@ impl ToChalk for GenericPredicate {
     ) -> GenericPredicate {
         // we don't produce any where clauses with binders and can't currently deal with them
         match where_clause
-            .value
+            .skip_binders()
             .shifted_out(&Interner)
             .expect("unexpected bound vars in where clause")
         {
@@ -521,7 +568,7 @@ impl ToChalk for Arc<super::TraitEnvironment> {
                 pred.clone().to_chalk(db).cast(&Interner);
             clauses.push(program_clause.into_from_env_clause(&Interner));
         }
-        chalk_ir::Environment::new().add_clauses(clauses)
+        chalk_ir::Environment::new(&Interner).add_clauses(&Interner, clauses)
     }
 
     fn from_chalk(
@@ -603,10 +650,10 @@ impl ToChalk for builtin::BuiltinImplAssocTyValueData {
 }
 
 fn make_binders<T>(value: T, num_vars: usize) -> chalk_ir::Binders<T> {
-    chalk_ir::Binders {
+    chalk_ir::Binders::new(
+        std::iter::repeat(chalk_ir::ParameterKind::Ty(())).take(num_vars).collect(),
         value,
-        binders: std::iter::repeat(chalk_ir::ParameterKind::Ty(())).take(num_vars).collect(),
-    }
+    )
 }
 
 fn convert_where_clauses(
@@ -626,6 +673,55 @@ fn convert_where_clauses(
     result
 }
 
+fn generic_predicate_to_inline_bound(
+    db: &dyn HirDatabase,
+    pred: &GenericPredicate,
+    self_ty: &Ty,
+) -> Option<chalk_rust_ir::InlineBound<Interner>> {
+    // An InlineBound is like a GenericPredicate, except the self type is left out.
+    // We don't have a special type for this, but Chalk does.
+    match pred {
+        GenericPredicate::Implemented(trait_ref) => {
+            if &trait_ref.substs[0] != self_ty {
+                // we can only convert predicates back to type bounds if they
+                // have the expected self type
+                return None;
+            }
+            let args_no_self = trait_ref.substs[1..]
+                .iter()
+                .map(|ty| ty.clone().to_chalk(db).cast(&Interner))
+                .collect();
+            let trait_bound =
+                chalk_rust_ir::TraitBound { trait_id: trait_ref.trait_.to_chalk(db), args_no_self };
+            Some(chalk_rust_ir::InlineBound::TraitBound(trait_bound))
+        }
+        GenericPredicate::Projection(proj) => {
+            if &proj.projection_ty.parameters[0] != self_ty {
+                return None;
+            }
+            let trait_ = match proj.projection_ty.associated_ty.lookup(db.upcast()).container {
+                AssocContainerId::TraitId(t) => t,
+                _ => panic!("associated type not in trait"),
+            };
+            let args_no_self = proj.projection_ty.parameters[1..]
+                .iter()
+                .map(|ty| ty.clone().to_chalk(db).cast(&Interner))
+                .collect();
+            let alias_eq_bound = chalk_rust_ir::AliasEqBound {
+                value: proj.ty.clone().to_chalk(db),
+                trait_bound: chalk_rust_ir::TraitBound {
+                    trait_id: trait_.to_chalk(db),
+                    args_no_self,
+                },
+                associated_ty_id: proj.projection_ty.associated_ty.to_chalk(db),
+                parameters: Vec::new(), // FIXME we don't support generic associated types yet
+            };
+            Some(chalk_rust_ir::InlineBound::AliasEqBound(alias_eq_bound))
+        }
+        GenericPredicate::Error => None,
+    }
+}
+
 impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
     fn associated_ty_data(&self, id: AssocTypeId) -> Arc<AssociatedTyDatum> {
         self.db.associated_ty_data(id)
@@ -647,19 +743,22 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
         debug!("impls_for_trait {:?}", trait_id);
         let trait_: hir_def::TraitId = from_chalk(self.db, trait_id);
 
+        let ty: Ty = from_chalk(self.db, parameters[0].assert_ty_ref(&Interner).clone());
+
+        let self_ty_fp = TyFingerprint::for_impl(&ty);
+
         // Note: Since we're using impls_for_trait, only impls where the trait
         // can be resolved should ever reach Chalk. `impl_datum` relies on that
         // and will panic if the trait can't be resolved.
         let mut result: Vec<_> = self
             .db
-            .impls_for_trait(self.krate, trait_)
+            .impls_for_trait(self.krate, trait_, self_ty_fp)
             .iter()
             .copied()
             .map(Impl::ImplDef)
             .map(|impl_| impl_.to_chalk(self.db))
             .collect();
 
-        let ty: Ty = from_chalk(self.db, parameters[0].assert_ty_ref(&Interner).clone());
         let arg: Option<Ty> =
             parameters.get(1).map(|p| from_chalk(self.db, p.assert_ty_ref(&Interner).clone()));
 
@@ -693,6 +792,12 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
     fn interner(&self) -> &Interner {
         &Interner
     }
+    fn well_known_trait_id(
+        &self,
+        _well_known_trait: chalk_rust_ir::WellKnownTrait,
+    ) -> chalk_ir::TraitId<Interner> {
+        unimplemented!()
+    }
 }
 
 pub(crate) fn associated_ty_data_query(
@@ -705,12 +810,25 @@ pub(crate) fn associated_ty_data_query(
         AssocContainerId::TraitId(t) => t,
         _ => panic!("associated type not in trait"),
     };
+
+    // Lower bounds -- we could/should maybe move this to a separate query in `lower`
+    let type_alias_data = db.type_alias_data(type_alias);
     let generic_params = generics(db.upcast(), type_alias.into());
-    let bound_data = chalk_rust_ir::AssociatedTyDatumBound {
-        // FIXME add bounds and where clauses
-        bounds: vec![],
-        where_clauses: vec![],
-    };
+    let bound_vars = Substs::bound_vars(&generic_params);
+    let resolver = hir_def::resolver::HasResolver::resolver(type_alias, db.upcast());
+    let ctx = crate::TyLoweringContext::new(db, &resolver)
+        .with_type_param_mode(crate::lower::TypeParamLoweringMode::Variable);
+    let self_ty = Ty::Bound(crate::BoundVar::new(crate::DebruijnIndex::INNERMOST, 0));
+    let bounds = type_alias_data
+        .bounds
+        .iter()
+        .flat_map(|bound| GenericPredicate::from_type_bound(&ctx, bound, self_ty.clone()))
+        .filter_map(|pred| generic_predicate_to_inline_bound(db, &pred, &self_ty))
+        .map(|bound| make_binders(bound.shifted_in(&Interner), 0))
+        .collect();
+
+    let where_clauses = convert_where_clauses(db, type_alias.into(), &bound_vars);
+    let bound_data = chalk_rust_ir::AssociatedTyDatumBound { bounds, where_clauses };
     let datum = AssociatedTyDatum {
         trait_id: trait_.to_chalk(db),
         id,
diff --git a/crates/ra_hir_ty/src/traits/chalk/tls.rs b/crates/ra_hir_ty/src/traits/chalk/tls.rs
index d9bbb54a5..fa8e4d1ad 100644
--- a/crates/ra_hir_ty/src/traits/chalk/tls.rs
+++ b/crates/ra_hir_ty/src/traits/chalk/tls.rs
@@ -2,10 +2,11 @@
 use std::fmt;
 
 use chalk_ir::{AliasTy, Goal, Goals, Lifetime, Parameter, ProgramClauseImplication, TypeName};
+use itertools::Itertools;
 
 use super::{from_chalk, Interner};
 use crate::{db::HirDatabase, CallableDef, TypeCtor};
-use hir_def::{AdtId, AssocContainerId, Lookup, TypeAliasId};
+use hir_def::{AdtId, AssocContainerId, DefWithBodyId, Lookup, TypeAliasId};
 
 pub use unsafe_tls::{set_current_program, with_current_program};
 
@@ -69,7 +70,27 @@ impl DebugContext<'_> {
                 write!(f, "{}::{}", trait_name, name)?;
             }
             TypeCtor::Closure { def, expr } => {
-                write!(f, "{{closure {:?} in {:?}}}", expr.into_raw(), def)?;
+                write!(f, "{{closure {:?} in ", expr.into_raw())?;
+                match def {
+                    DefWithBodyId::FunctionId(func) => {
+                        write!(f, "fn {}", self.0.function_data(func).name)?
+                    }
+                    DefWithBodyId::StaticId(s) => {
+                        if let Some(name) = self.0.static_data(s).name.as_ref() {
+                            write!(f, "body of static {}", name)?;
+                        } else {
+                            write!(f, "body of unnamed static {:?}", s)?;
+                        }
+                    }
+                    DefWithBodyId::ConstId(c) => {
+                        if let Some(name) = self.0.const_data(c).name.as_ref() {
+                            write!(f, "body of const {}", name)?;
+                        } else {
+                            write!(f, "body of unnamed const {:?}", c)?;
+                        }
+                    }
+                };
+                write!(f, "}}")?;
             }
         }
         Ok(())
@@ -113,14 +134,15 @@ impl DebugContext<'_> {
         };
         let trait_data = self.0.trait_data(trait_);
         let params = alias.substitution.parameters(&Interner);
-        write!(
-            fmt,
-            "<{:?} as {}<{:?}>>::{}",
-            &params[0],
-            trait_data.name,
-            &params[1..],
-            type_alias_data.name
-        )
+        write!(fmt, "<{:?} as {}", &params[0], trait_data.name,)?;
+        if params.len() > 1 {
+            write!(
+                fmt,
+                "<{}>",
+                &params[1..].iter().format_with(", ", |x, f| f(&format_args!("{:?}", x))),
+            )?;
+        }
+        write!(fmt, ">::{}", type_alias_data.name)
     }
 
     pub fn debug_ty(