Merging upstream version 1.67.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

17 files changed, 580 insertions, 166 deletions

diff --git a/src/tools/rust-analyzer/crates/hir-ty/Cargo.toml b/src/tools/rust-analyzer/crates/hir-ty/Cargo.toml
index ed13275ba..a1d6835bf 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/Cargo.toml
+++ b/src/tools/rust-analyzer/crates/hir-ty/Cargo.toml
@@ -4,7 +4,7 @@ version = "0.0.0"
 description = "TBD"
 license = "MIT OR Apache-2.0"
 edition = "2021"
-rust-version = "1.57"
+rust-version = "1.65"
 
 [lib]
 doctest = false
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/chalk_ext.rs b/src/tools/rust-analyzer/crates/hir-ty/src/chalk_ext.rs
index e2099d7e5..996b42f5b 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/chalk_ext.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/chalk_ext.rs
@@ -11,9 +11,9 @@ use syntax::SmolStr;
 
 use crate::{
     db::HirDatabase, from_assoc_type_id, from_chalk_trait_id, from_foreign_def_id,
-    from_placeholder_idx, to_chalk_trait_id, AdtId, AliasEq, AliasTy, Binders, CallableDefId,
-    CallableSig, FnPointer, ImplTraitId, Interner, Lifetime, ProjectionTy, QuantifiedWhereClause,
-    Substitution, TraitRef, Ty, TyBuilder, TyKind, WhereClause,
+    from_placeholder_idx, to_chalk_trait_id, utils::generics, AdtId, AliasEq, AliasTy, Binders,
+    CallableDefId, CallableSig, FnPointer, ImplTraitId, Interner, Lifetime, ProjectionTy,
+    QuantifiedWhereClause, Substitution, TraitRef, Ty, TyBuilder, TyKind, WhereClause,
 };
 
 pub trait TyExt {
@@ -338,10 +338,13 @@ pub trait ProjectionTyExt {
 
 impl ProjectionTyExt for ProjectionTy {
     fn trait_ref(&self, db: &dyn HirDatabase) -> TraitRef {
-        TraitRef {
-            trait_id: to_chalk_trait_id(self.trait_(db)),
-            substitution: self.substitution.clone(),
-        }
+        // FIXME: something like `Split` trait from chalk-solve might be nice.
+        let generics = generics(db.upcast(), from_assoc_type_id(self.associated_ty_id).into());
+        let substitution = Substitution::from_iter(
+            Interner,
+            self.substitution.iter(Interner).skip(generics.len_self()),
+        );
+        TraitRef { trait_id: to_chalk_trait_id(self.trait_(db)), substitution }
     }
 
     fn trait_(&self, db: &dyn HirDatabase) -> TraitId {
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/display.rs b/src/tools/rust-analyzer/crates/hir-ty/src/display.rs
index 0221f922f..a22a4b170 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/display.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/display.rs
@@ -289,16 +289,18 @@ impl HirDisplay for ProjectionTy {
             return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
 
-        let trait_ = f.db.trait_data(self.trait_(f.db));
+        let trait_ref = self.trait_ref(f.db);
         write!(f, "<")?;
-        self.self_type_parameter(f.db).hir_fmt(f)?;
-        write!(f, " as {}", trait_.name)?;
-        if self.substitution.len(Interner) > 1 {
+        fmt_trait_ref(&trait_ref, f, true)?;
+        write!(f, ">::{}", f.db.type_alias_data(from_assoc_type_id(self.associated_ty_id)).name)?;
+        let proj_params_count =
+            self.substitution.len(Interner) - trait_ref.substitution.len(Interner);
+        let proj_params = &self.substitution.as_slice(Interner)[..proj_params_count];
+        if !proj_params.is_empty() {
             write!(f, "<")?;
-            f.write_joined(&self.substitution.as_slice(Interner)[1..], ", ")?;
+            f.write_joined(proj_params, ", ")?;
             write!(f, ">")?;
         }
-        write!(f, ">::{}", f.db.type_alias_data(from_assoc_type_id(self.associated_ty_id)).name)?;
         Ok(())
     }
 }
@@ -641,9 +643,12 @@ impl HirDisplay for Ty {
                 // Use placeholder associated types when the target is test (https://rust-lang.github.io/chalk/book/clauses/type_equality.html#placeholder-associated-types)
                 if f.display_target.is_test() {
                     write!(f, "{}::{}", trait_.name, type_alias_data.name)?;
+                    // Note that the generic args for the associated type come before those for the
+                    // trait (including the self type).
+                    // FIXME: reconsider the generic args order upon formatting?
                     if parameters.len(Interner) > 0 {
                         write!(f, "<")?;
-                        f.write_joined(&*parameters.as_slice(Interner), ", ")?;
+                        f.write_joined(parameters.as_slice(Interner), ", ")?;
                         write!(f, ">")?;
                     }
                 } else {
@@ -972,9 +977,20 @@ fn write_bounds_like_dyn_trait(
                     angle_open = true;
                 }
                 if let AliasTy::Projection(proj) = alias {
-                    let type_alias =
-                        f.db.type_alias_data(from_assoc_type_id(proj.associated_ty_id));
-                    write!(f, "{} = ", type_alias.name)?;
+                    let assoc_ty_id = from_assoc_type_id(proj.associated_ty_id);
+                    let type_alias = f.db.type_alias_data(assoc_ty_id);
+                    write!(f, "{}", type_alias.name)?;
+
+                    let proj_arg_count = generics(f.db.upcast(), assoc_ty_id.into()).len_self();
+                    if proj_arg_count > 0 {
+                        write!(f, "<")?;
+                        f.write_joined(
+                            &proj.substitution.as_slice(Interner)[..proj_arg_count],
+                            ", ",
+                        )?;
+                        write!(f, ">")?;
+                    }
+                    write!(f, " = ")?;
                 }
                 ty.hir_fmt(f)?;
             }
@@ -1171,8 +1187,11 @@ impl HirDisplay for TypeRef {
                 inner.hir_fmt(f)?;
                 write!(f, "]")?;
             }
-            TypeRef::Fn(parameters, is_varargs) => {
+            &TypeRef::Fn(ref parameters, is_varargs, is_unsafe) => {
                 // FIXME: Function pointer qualifiers.
+                if is_unsafe {
+                    write!(f, "unsafe ")?;
+                }
                 write!(f, "fn(")?;
                 if let Some(((_, return_type), function_parameters)) = parameters.split_last() {
                     for index in 0..function_parameters.len() {
@@ -1187,7 +1206,7 @@ impl HirDisplay for TypeRef {
                             write!(f, ", ")?;
                         }
                     }
-                    if *is_varargs {
+                    if is_varargs {
                         write!(f, "{}...", if parameters.len() == 1 { "" } else { ", " })?;
                     }
                     write!(f, ")")?;
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/infer.rs b/src/tools/rust-analyzer/crates/hir-ty/src/infer.rs
index 0efff651c..0b3c23f57 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/infer.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/infer.rs
@@ -1020,7 +1020,7 @@ impl Expectation {
     /// The primary use case is where the expected type is a fat pointer,
     /// like `&[isize]`. For example, consider the following statement:
     ///
-    ///    let x: &[isize] = &[1, 2, 3];
+    ///     let x: &[isize] = &[1, 2, 3];
     ///
     /// In this case, the expected type for the `&[1, 2, 3]` expression is
     /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/infer/expr.rs b/src/tools/rust-analyzer/crates/hir-ty/src/infer/expr.rs
index f56108b26..b1f4de826 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/infer/expr.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/infer/expr.rs
@@ -85,6 +85,7 @@ impl<'a> InferenceContext<'a> {
         let ty = match &self.body[tgt_expr] {
             Expr::Missing => self.err_ty(),
             &Expr::If { condition, then_branch, else_branch } => {
+                let expected = &expected.adjust_for_branches(&mut self.table);
                 self.infer_expr(
                     condition,
                     &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(Interner)),
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/infer/path.rs b/src/tools/rust-analyzer/crates/hir-ty/src/infer/path.rs
index 7a4754cdc..ebe9d6fb5 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/infer/path.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/infer/path.rs
@@ -157,7 +157,7 @@ impl<'a> InferenceContext<'a> {
                     remaining_segments_for_ty,
                     true,
                 );
-                if let TyKind::Error = ty.kind(Interner) {
+                if ty.is_unknown() {
                     return None;
                 }
 
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/infer/unify.rs b/src/tools/rust-analyzer/crates/hir-ty/src/infer/unify.rs
index b00e3216b..12f45f00f 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/infer/unify.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/infer/unify.rs
@@ -340,8 +340,8 @@ impl<'a> InferenceTable<'a> {
         self.resolve_with_fallback(t, &|_, _, d, _| d)
     }
 
-    /// Unify two types and register new trait goals that arise from that.
-    pub(crate) fn unify(&mut self, ty1: &Ty, ty2: &Ty) -> bool {
+    /// Unify two relatable values (e.g. `Ty`) and register new trait goals that arise from that.
+    pub(crate) fn unify<T: ?Sized + Zip<Interner>>(&mut self, ty1: &T, ty2: &T) -> bool {
         let result = match self.try_unify(ty1, ty2) {
             Ok(r) => r,
             Err(_) => return false,
@@ -350,9 +350,13 @@ impl<'a> InferenceTable<'a> {
         true
     }
 
-    /// Unify two types and return new trait goals arising from it, so the
+    /// Unify two relatable values (e.g. `Ty`) and return new trait goals arising from it, so the
     /// caller needs to deal with them.
-    pub(crate) fn try_unify<T: Zip<Interner>>(&mut self, t1: &T, t2: &T) -> InferResult<()> {
+    pub(crate) fn try_unify<T: ?Sized + Zip<Interner>>(
+        &mut self,
+        t1: &T,
+        t2: &T,
+    ) -> InferResult<()> {
         match self.var_unification_table.relate(
             Interner,
             &self.db,
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/lib.rs b/src/tools/rust-analyzer/crates/hir-ty/src/lib.rs
index c4b700cbc..39514fc44 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/lib.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/lib.rs
@@ -38,10 +38,12 @@ use std::sync::Arc;
 use chalk_ir::{
     fold::{Shift, TypeFoldable},
     interner::HasInterner,
-    NoSolution,
+    NoSolution, UniverseIndex,
 };
 use hir_def::{expr::ExprId, type_ref::Rawness, TypeOrConstParamId};
+use hir_expand::name;
 use itertools::Either;
+use traits::FnTrait;
 use utils::Generics;
 
 use crate::{consteval::unknown_const, db::HirDatabase, utils::generics};
@@ -51,7 +53,7 @@ pub use builder::{ParamKind, TyBuilder};
 pub use chalk_ext::*;
 pub use infer::{
     could_coerce, could_unify, Adjust, Adjustment, AutoBorrow, BindingMode, InferenceDiagnostic,
-    InferenceResult,
+    InferenceResult, OverloadedDeref, PointerCast,
 };
 pub use interner::Interner;
 pub use lower::{
@@ -81,7 +83,20 @@ pub type PlaceholderIndex = chalk_ir::PlaceholderIndex;
 pub type VariableKind = chalk_ir::VariableKind<Interner>;
 pub type VariableKinds = chalk_ir::VariableKinds<Interner>;
 pub type CanonicalVarKinds = chalk_ir::CanonicalVarKinds<Interner>;
+/// Represents generic parameters and an item bound by them. When the item has parent, the binders
+/// also contain the generic parameters for its parent. See chalk's documentation for details.
+///
+/// One thing to keep in mind when working with `Binders` (and `Substitution`s, which represent
+/// generic arguments) in rust-analyzer is that the ordering within *is* significant - the generic
+/// parameters/arguments for an item MUST come before those for its parent. This is to facilitate
+/// the integration with chalk-solve, which mildly puts constraints as such. See #13335 for its
+/// motivation in detail.
 pub type Binders<T> = chalk_ir::Binders<T>;
+/// Interned list of generic arguments for an item. When an item has parent, the `Substitution` for
+/// it contains generic arguments for both its parent and itself. See chalk's documentation for
+/// details.
+///
+/// See `Binders` for the constraint on the ordering.
 pub type Substitution = chalk_ir::Substitution<Interner>;
 pub type GenericArg = chalk_ir::GenericArg<Interner>;
 pub type GenericArgData = chalk_ir::GenericArgData<Interner>;
@@ -124,14 +139,6 @@ pub type ConstrainedSubst = chalk_ir::ConstrainedSubst<Interner>;
 pub type Guidance = chalk_solve::Guidance<Interner>;
 pub type WhereClause = chalk_ir::WhereClause<Interner>;
 
-// FIXME: get rid of this
-pub fn subst_prefix(s: &Substitution, n: usize) -> Substitution {
-    Substitution::from_iter(
-        Interner,
-        s.as_slice(Interner)[..std::cmp::min(s.len(Interner), n)].iter().cloned(),
-    )
-}
-
 /// Return an index of a parameter in the generic type parameter list by it's id.
 pub fn param_idx(db: &dyn HirDatabase, id: TypeOrConstParamId) -> Option<usize> {
     generics(db.upcast(), id.parent).param_idx(id)
@@ -203,6 +210,7 @@ pub(crate) fn make_binders<T: HasInterner<Interner = Interner>>(
 pub struct CallableSig {
     params_and_return: Arc<[Ty]>,
     is_varargs: bool,
+    safety: Safety,
 }
 
 has_interner!(CallableSig);
@@ -211,9 +219,14 @@ has_interner!(CallableSig);
 pub type PolyFnSig = Binders<CallableSig>;
 
 impl CallableSig {
-    pub fn from_params_and_return(mut params: Vec<Ty>, ret: Ty, is_varargs: bool) -> CallableSig {
+    pub fn from_params_and_return(
+        mut params: Vec<Ty>,
+        ret: Ty,
+        is_varargs: bool,
+        safety: Safety,
+    ) -> CallableSig {
         params.push(ret);
-        CallableSig { params_and_return: params.into(), is_varargs }
+        CallableSig { params_and_return: params.into(), is_varargs, safety }
     }
 
     pub fn from_fn_ptr(fn_ptr: &FnPointer) -> CallableSig {
@@ -230,13 +243,14 @@ impl CallableSig {
                 .map(|arg| arg.assert_ty_ref(Interner).clone())
                 .collect(),
             is_varargs: fn_ptr.sig.variadic,
+            safety: fn_ptr.sig.safety,
         }
     }
 
     pub fn to_fn_ptr(&self) -> FnPointer {
         FnPointer {
             num_binders: 0,
-            sig: FnSig { abi: (), safety: Safety::Safe, variadic: self.is_varargs },
+            sig: FnSig { abi: (), safety: self.safety, variadic: self.is_varargs },
             substitution: FnSubst(Substitution::from_iter(
                 Interner,
                 self.params_and_return.iter().cloned(),
@@ -261,7 +275,11 @@ impl TypeFoldable<Interner> for CallableSig {
     ) -> Result<Self, E> {
         let vec = self.params_and_return.to_vec();
         let folded = vec.try_fold_with(folder, outer_binder)?;
-        Ok(CallableSig { params_and_return: folded.into(), is_varargs: self.is_varargs })
+        Ok(CallableSig {
+            params_and_return: folded.into(),
+            is_varargs: self.is_varargs,
+            safety: self.safety,
+        })
     }
 }
 
@@ -382,7 +400,6 @@ pub(crate) fn fold_tys_and_consts<T: HasInterner<Interner = Interner> + TypeFold
 pub fn replace_errors_with_variables<T>(t: &T) -> Canonical<T>
 where
     T: HasInterner<Interner = Interner> + TypeFoldable<Interner> + Clone,
-    T: HasInterner<Interner = Interner>,
 {
     use chalk_ir::{
         fold::{FallibleTypeFolder, TypeSuperFoldable},
@@ -504,3 +521,64 @@ where
     });
     Canonical { value, binders: chalk_ir::CanonicalVarKinds::from_iter(Interner, kinds) }
 }
+
+pub fn callable_sig_from_fnonce(
+    self_ty: &Ty,
+    env: Arc<TraitEnvironment>,
+    db: &dyn HirDatabase,
+) -> Option<CallableSig> {
+    let krate = env.krate;
+    let fn_once_trait = FnTrait::FnOnce.get_id(db, krate)?;
+    let output_assoc_type = db.trait_data(fn_once_trait).associated_type_by_name(&name![Output])?;
+
+    let b = TyBuilder::trait_ref(db, fn_once_trait);
+    if b.remaining() != 2 {
+        return None;
+    }
+    let fn_once = b.push(self_ty.clone()).fill_with_bound_vars(DebruijnIndex::INNERMOST, 0).build();
+    let kinds = fn_once
+        .substitution
+        .iter(Interner)
+        .skip(1)
+        .map(|x| {
+            let vk = match x.data(Interner) {
+                chalk_ir::GenericArgData::Ty(_) => {
+                    chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General)
+                }
+                chalk_ir::GenericArgData::Lifetime(_) => chalk_ir::VariableKind::Lifetime,
+                chalk_ir::GenericArgData::Const(c) => {
+                    chalk_ir::VariableKind::Const(c.data(Interner).ty.clone())
+                }
+            };
+            chalk_ir::WithKind::new(vk, UniverseIndex::ROOT)
+        })
+        .collect::<Vec<_>>();
+
+    // FIXME: chalk refuses to solve `<Self as FnOnce<^0.0>>::Output == ^0.1`, so we first solve
+    // `<Self as FnOnce<^0.0>>` and then replace `^0.0` with the concrete argument tuple.
+    let trait_env = env.env.clone();
+    let obligation = InEnvironment { goal: fn_once.cast(Interner), environment: trait_env };
+    let canonical =
+        Canonical { binders: CanonicalVarKinds::from_iter(Interner, kinds), value: obligation };
+    let subst = match db.trait_solve(krate, canonical) {
+        Some(Solution::Unique(vars)) => vars.value.subst,
+        _ => return None,
+    };
+    let args = subst.at(Interner, 0).ty(Interner)?;
+    let params = match args.kind(Interner) {
+        chalk_ir::TyKind::Tuple(_, subst) => {
+            subst.iter(Interner).filter_map(|arg| arg.ty(Interner).cloned()).collect::<Vec<_>>()
+        }
+        _ => return None,
+    };
+
+    let fn_once =
+        TyBuilder::trait_ref(db, fn_once_trait).push(self_ty.clone()).push(args.clone()).build();
+    let projection =
+        TyBuilder::assoc_type_projection(db, output_assoc_type, Some(fn_once.substitution.clone()))
+            .build();
+
+    let ret_ty = db.normalize_projection(projection, env);
+
+    Some(CallableSig::from_params_and_return(params, ret_ty.clone(), false, Safety::Safe))
+}
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/lower.rs b/src/tools/rust-analyzer/crates/hir-ty/src/lower.rs
index 223d705b1..baf9842d5 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/lower.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/lower.rs
@@ -227,13 +227,17 @@ impl<'a> TyLoweringContext<'a> {
                     .intern(Interner)
             }
             TypeRef::Placeholder => TyKind::Error.intern(Interner),
-            TypeRef::Fn(params, is_varargs) => {
+            &TypeRef::Fn(ref params, variadic, is_unsafe) => {
                 let substs = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
                     Substitution::from_iter(Interner, params.iter().map(|(_, tr)| ctx.lower_ty(tr)))
                 });
                 TyKind::Function(FnPointer {
                     num_binders: 0, // FIXME lower `for<'a> fn()` correctly
-                    sig: FnSig { abi: (), safety: Safety::Safe, variadic: *is_varargs },
+                    sig: FnSig {
+                        abi: (),
+                        safety: if is_unsafe { Safety::Unsafe } else { Safety::Safe },
+                        variadic,
+                    },
                     substitution: FnSubst(substs),
                 })
                 .intern(Interner)
@@ -447,12 +451,31 @@ impl<'a> TyLoweringContext<'a> {
                             .db
                             .trait_data(trait_ref.hir_trait_id())
                             .associated_type_by_name(segment.name);
+
                         match found {
                             Some(associated_ty) => {
-                                // FIXME handle type parameters on the segment
+                                // FIXME: `substs_from_path_segment()` pushes `TyKind::Error` for every parent
+                                // generic params. It's inefficient to splice the `Substitution`s, so we may want
+                                // that method to optionally take parent `Substitution` as we already know them at
+                                // this point (`trait_ref.substitution`).
+                                let substitution = self.substs_from_path_segment(
+                                    segment,
+                                    Some(associated_ty.into()),
+                                    false,
+                                    None,
+                                );
+                                let len_self =
+                                    generics(self.db.upcast(), associated_ty.into()).len_self();
+                                let substitution = Substitution::from_iter(
+                                    Interner,
+                                    substitution
+                                        .iter(Interner)
+                                        .take(len_self)
+                                        .chain(trait_ref.substitution.iter(Interner)),
+                                );
                                 TyKind::Alias(AliasTy::Projection(ProjectionTy {
                                     associated_ty_id: to_assoc_type_id(associated_ty),
-                                    substitution: trait_ref.substitution,
+                                    substitution,
                                 }))
                                 .intern(Interner)
                             }
@@ -590,36 +613,48 @@ impl<'a> TyLoweringContext<'a> {
             res,
             Some(segment.name.clone()),
             move |name, t, associated_ty| {
-                if name == segment.name {
-                    let substs = match self.type_param_mode {
-                        ParamLoweringMode::Placeholder => {
-                            // if we're lowering to placeholders, we have to put
-                            // them in now
-                            let generics = generics(
-                                self.db.upcast(),
-                                self.resolver
-                                    .generic_def()
-                                    .expect("there should be generics if there's a generic param"),
-                            );
-                            let s = generics.placeholder_subst(self.db);
-                            s.apply(t.substitution.clone(), Interner)
-                        }
-                        ParamLoweringMode::Variable => t.substitution.clone(),
-                    };
-                    // We need to shift in the bound vars, since
-                    // associated_type_shorthand_candidates does not do that
-                    let substs = substs.shifted_in_from(Interner, self.in_binders);
-                    // FIXME handle type parameters on the segment
-                    Some(
-                        TyKind::Alias(AliasTy::Projection(ProjectionTy {
-                            associated_ty_id: to_assoc_type_id(associated_ty),
-                            substitution: substs,
-                        }))
-                        .intern(Interner),
-                    )
-                } else {
-                    None
+                if name != segment.name {
+                    return None;
                 }
+
+                // FIXME: `substs_from_path_segment()` pushes `TyKind::Error` for every parent
+                // generic params. It's inefficient to splice the `Substitution`s, so we may want
+                // that method to optionally take parent `Substitution` as we already know them at
+                // this point (`t.substitution`).
+                let substs = self.substs_from_path_segment(
+                    segment.clone(),
+                    Some(associated_ty.into()),
+                    false,
+                    None,
+                );
+
+                let len_self = generics(self.db.upcast(), associated_ty.into()).len_self();
+
+                let substs = Substitution::from_iter(
+                    Interner,
+                    substs.iter(Interner).take(len_self).chain(t.substitution.iter(Interner)),
+                );
+
+                let substs = match self.type_param_mode {
+                    ParamLoweringMode::Placeholder => {
+                        // if we're lowering to placeholders, we have to put
+                        // them in now
+                        let generics = generics(self.db.upcast(), def);
+                        let s = generics.placeholder_subst(self.db);
+                        s.apply(substs, Interner)
+                    }
+                    ParamLoweringMode::Variable => substs,
+                };
+                // We need to shift in the bound vars, since
+                // associated_type_shorthand_candidates does not do that
+                let substs = substs.shifted_in_from(Interner, self.in_binders);
+                Some(
+                    TyKind::Alias(AliasTy::Projection(ProjectionTy {
+                        associated_ty_id: to_assoc_type_id(associated_ty),
+                        substitution: substs,
+                    }))
+                    .intern(Interner),
+                )
             },
         );
 
@@ -777,7 +812,15 @@ impl<'a> TyLoweringContext<'a> {
         // handle defaults. In expression or pattern path segments without
         // explicitly specified type arguments, missing type arguments are inferred
         // (i.e. defaults aren't used).
-        if !infer_args || had_explicit_args {
+        // Generic parameters for associated types are not supposed to have defaults, so we just
+        // ignore them.
+        let is_assoc_ty = if let GenericDefId::TypeAliasId(id) = def {
+            let container = id.lookup(self.db.upcast()).container;
+            matches!(container, ItemContainerId::TraitId(_))
+        } else {
+            false
+        };
+        if !is_assoc_ty && (!infer_args || had_explicit_args) {
             let defaults = self.db.generic_defaults(def);
             assert_eq!(total_len, defaults.len());
             let parent_from = item_len - substs.len();
@@ -966,9 +1009,28 @@ impl<'a> TyLoweringContext<'a> {
                     None => return SmallVec::new(),
                     Some(t) => t,
                 };
+                // FIXME: `substs_from_path_segment()` pushes `TyKind::Error` for every parent
+                // generic params. It's inefficient to splice the `Substitution`s, so we may want
+                // that method to optionally take parent `Substitution` as we already know them at
+                // this point (`super_trait_ref.substitution`).
+                let substitution = self.substs_from_path_segment(
+                    // FIXME: This is hack. We shouldn't really build `PathSegment` directly.
+                    PathSegment { name: &binding.name, args_and_bindings: binding.args.as_deref() },
+                    Some(associated_ty.into()),
+                    false, // this is not relevant
+                    Some(super_trait_ref.self_type_parameter(Interner)),
+                );
+                let self_params = generics(self.db.upcast(), associated_ty.into()).len_self();
+                let substitution = Substitution::from_iter(
+                    Interner,
+                    substitution
+                        .iter(Interner)
+                        .take(self_params)
+                        .chain(super_trait_ref.substitution.iter(Interner)),
+                );
                 let projection_ty = ProjectionTy {
                     associated_ty_id: to_assoc_type_id(associated_ty),
-                    substitution: super_trait_ref.substitution,
+                    substitution,
                 };
                 let mut preds: SmallVec<[_; 1]> = SmallVec::with_capacity(
                     binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
@@ -1515,7 +1577,12 @@ fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
         .with_type_param_mode(ParamLoweringMode::Variable);
     let ret = ctx_ret.lower_ty(&data.ret_type);
     let generics = generics(db.upcast(), def.into());
-    let sig = CallableSig::from_params_and_return(params, ret, data.is_varargs());
+    let sig = CallableSig::from_params_and_return(
+        params,
+        ret,
+        data.is_varargs(),
+        if data.has_unsafe_kw() { Safety::Unsafe } else { Safety::Safe },
+    );
     make_binders(db, &generics, sig)
 }
 
@@ -1559,7 +1626,7 @@ fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnS
         TyLoweringContext::new(db, &resolver).with_type_param_mode(ParamLoweringMode::Variable);
     let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
     let (ret, binders) = type_for_adt(db, def.into()).into_value_and_skipped_binders();
-    Binders::new(binders, CallableSig::from_params_and_return(params, ret, false))
+    Binders::new(binders, CallableSig::from_params_and_return(params, ret, false, Safety::Safe))
 }
 
 /// Build the type of a tuple struct constructor.
@@ -1586,7 +1653,7 @@ fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId)
         TyLoweringContext::new(db, &resolver).with_type_param_mode(ParamLoweringMode::Variable);
     let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
     let (ret, binders) = type_for_adt(db, def.parent.into()).into_value_and_skipped_binders();
-    Binders::new(binders, CallableSig::from_params_and_return(params, ret, false))
+    Binders::new(binders, CallableSig::from_params_and_return(params, ret, false, Safety::Safe))
 }
 
 /// Build the type of a tuple enum variant constructor.
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/method_resolution.rs b/src/tools/rust-analyzer/crates/hir-ty/src/method_resolution.rs
index 3a1a3f4fd..8bcfa2728 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/method_resolution.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/method_resolution.rs
@@ -22,10 +22,10 @@ use crate::{
     from_foreign_def_id,
     infer::{unify::InferenceTable, Adjust, Adjustment, AutoBorrow, OverloadedDeref, PointerCast},
     primitive::{FloatTy, IntTy, UintTy},
-    static_lifetime,
+    static_lifetime, to_chalk_trait_id,
     utils::all_super_traits,
     AdtId, Canonical, CanonicalVarKinds, DebruijnIndex, ForeignDefId, InEnvironment, Interner,
-    Scalar, TraitEnvironment, TraitRefExt, Ty, TyBuilder, TyExt, TyKind,
+    Scalar, Substitution, TraitEnvironment, TraitRef, TraitRefExt, Ty, TyBuilder, TyExt, TyKind,
 };
 
 /// This is used as a key for indexing impls.
@@ -541,7 +541,7 @@ pub struct ReceiverAdjustments {
 
 impl ReceiverAdjustments {
     pub(crate) fn apply(&self, table: &mut InferenceTable<'_>, ty: Ty) -> (Ty, Vec<Adjustment>) {
-        let mut ty = ty;
+        let mut ty = table.resolve_ty_shallow(&ty);
         let mut adjust = Vec::new();
         for _ in 0..self.autoderefs {
             match autoderef::autoderef_step(table, ty.clone()) {
@@ -624,52 +624,76 @@ pub(crate) fn iterate_method_candidates<T>(
     slot
 }
 
+/// Looks up the impl method that actually runs for the trait method `func`.
+///
+/// Returns `func` if it's not a method defined in a trait or the lookup failed.
 pub fn lookup_impl_method(
-    self_ty: &Ty,
     db: &dyn HirDatabase,
     env: Arc<TraitEnvironment>,
-    trait_: TraitId,
+    func: FunctionId,
+    fn_subst: Substitution,
+) -> FunctionId {
+    let trait_id = match func.lookup(db.upcast()).container {
+        ItemContainerId::TraitId(id) => id,
+        _ => return func,
+    };
+    let trait_params = db.generic_params(trait_id.into()).type_or_consts.len();
+    let fn_params = fn_subst.len(Interner) - trait_params;
+    let trait_ref = TraitRef {
+        trait_id: to_chalk_trait_id(trait_id),
+        substitution: Substitution::from_iter(Interner, fn_subst.iter(Interner).skip(fn_params)),
+    };
+
+    let name = &db.function_data(func).name;
+    lookup_impl_method_for_trait_ref(trait_ref, db, env, name).unwrap_or(func)
+}
+
+fn lookup_impl_method_for_trait_ref(
+    trait_ref: TraitRef,
+    db: &dyn HirDatabase,
+    env: Arc<TraitEnvironment>,
     name: &Name,
 ) -> Option<FunctionId> {
-    let self_ty_fp = TyFingerprint::for_trait_impl(self_ty)?;
-    let trait_impls = db.trait_impls_in_deps(env.krate);
-    let impls = trait_impls.for_trait_and_self_ty(trait_, self_ty_fp);
-    let mut table = InferenceTable::new(db, env.clone());
-    find_matching_impl(impls, &mut table, &self_ty).and_then(|data| {
-        data.items.iter().find_map(|it| match it {
-            AssocItemId::FunctionId(f) => (db.function_data(*f).name == *name).then(|| *f),
-            _ => None,
-        })
+    let self_ty = trait_ref.self_type_parameter(Interner);
+    let self_ty_fp = TyFingerprint::for_trait_impl(&self_ty)?;
+    let impls = db.trait_impls_in_deps(env.krate);
+    let impls = impls.for_trait_and_self_ty(trait_ref.hir_trait_id(), self_ty_fp);
+
+    let table = InferenceTable::new(db, env);
+
+    let impl_data = find_matching_impl(impls, table, trait_ref)?;
+    impl_data.items.iter().find_map(|it| match it {
+        AssocItemId::FunctionId(f) => (db.function_data(*f).name == *name).then(|| *f),
+        _ => None,
     })
 }
 
 fn find_matching_impl(
     mut impls: impl Iterator<Item = ImplId>,
-    table: &mut InferenceTable<'_>,
-    self_ty: &Ty,
+    mut table: InferenceTable<'_>,
+    actual_trait_ref: TraitRef,
 ) -> Option<Arc<ImplData>> {
     let db = table.db;
     loop {
         let impl_ = impls.next()?;
         let r = table.run_in_snapshot(|table| {
             let impl_data = db.impl_data(impl_);
-            let substs =
+            let impl_substs =
                 TyBuilder::subst_for_def(db, impl_, None).fill_with_inference_vars(table).build();
-            let impl_ty = db.impl_self_ty(impl_).substitute(Interner, &substs);
-
-            table
-                .unify(self_ty, &impl_ty)
-                .then(|| {
-                    let wh_goals =
-                        crate::chalk_db::convert_where_clauses(db, impl_.into(), &substs)
-                            .into_iter()
-                            .map(|b| b.cast(Interner));
+            let trait_ref = db
+                .impl_trait(impl_)
+                .expect("non-trait method in find_matching_impl")
+                .substitute(Interner, &impl_substs);
 
-                    let goal = crate::Goal::all(Interner, wh_goals);
+            if !table.unify(&trait_ref, &actual_trait_ref) {
+                return None;
+            }
 
-                    table.try_obligation(goal).map(|_| impl_data)
-                })
-                .flatten()
+            let wcs = crate::chalk_db::convert_where_clauses(db, impl_.into(), &impl_substs)
+                .into_iter()
+                .map(|b| b.cast(Interner));
+            let goal = crate::Goal::all(Interner, wcs);
+            table.try_obligation(goal).map(|_| impl_data)
         });
         if r.is_some() {
             break r;
@@ -1214,7 +1238,7 @@ fn is_valid_fn_candidate(
             let expected_receiver =
                 sig.map(|s| s.params()[0].clone()).substitute(Interner, &fn_subst);
 
-            check_that!(table.unify(&receiver_ty, &expected_receiver));
+            check_that!(table.unify(receiver_ty, &expected_receiver));
         }
 
         if let ItemContainerId::ImplId(impl_id) = container {
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/tests/coercion.rs b/src/tools/rust-analyzer/crates/hir-ty/src/tests/coercion.rs
index d301595bc..7e3aecc2a 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/tests/coercion.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/tests/coercion.rs
@@ -123,6 +123,23 @@ fn test() {
 }
 
 #[test]
+fn if_else_adjust_for_branches_discard_type_var() {
+    check_no_mismatches(
+        r#"
+fn test() {
+    let f = || {
+        if true {
+            &""
+        } else {
+            ""
+        }
+    };
+}
+"#,
+    );
+}
+
+#[test]
 fn match_first_coerce() {
     check_no_mismatches(
         r#"
@@ -183,6 +200,22 @@ fn test() {
 }
 
 #[test]
+fn match_adjust_for_branches_discard_type_var() {
+    check_no_mismatches(
+        r#"
+fn test() {
+    let f = || {
+        match 0i32 {
+            0i32 => &"",
+            _ => "",
+        }
+    };
+}
+"#,
+    );
+}
+
+#[test]
 fn return_coerce_unknown() {
     check_types(
         r"
@@ -357,7 +390,7 @@ fn test() {
     let f: fn(u32) -> isize = foo;
                            // ^^^ adjustments: Pointer(ReifyFnPointer)
     let f: unsafe fn(u32) -> isize = foo;
-                                  // ^^^ adjustments: Pointer(ReifyFnPointer)
+                                  // ^^^ adjustments: Pointer(ReifyFnPointer), Pointer(UnsafeFnPointer)
 }",
     );
 }
@@ -388,7 +421,10 @@ fn coerce_closure_to_fn_ptr() {
     check_no_mismatches(
         r"
 fn test() {
-    let f: fn(u32) -> isize = |x| { 1 };
+    let f: fn(u32) -> u32 = |x| x;
+                         // ^^^^^ adjustments: Pointer(ClosureFnPointer(Safe))
+    let f: unsafe fn(u32) -> u32 = |x| x;
+                                // ^^^^^ adjustments: Pointer(ClosureFnPointer(Unsafe))
 }",
     );
 }
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/tests/display_source_code.rs b/src/tools/rust-analyzer/crates/hir-ty/src/tests/display_source_code.rs
index 8a8ff08cf..425432479 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/tests/display_source_code.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/tests/display_source_code.rs
@@ -196,3 +196,34 @@ fn test(
 "#,
     );
 }
+
+#[test]
+fn projection_type_correct_arguments_order() {
+    check_types_source_code(
+        r#"
+trait Foo<T> {
+    type Assoc<U>;
+}
+fn f<T: Foo<i32>>(a: T::Assoc<usize>) {
+    a;
+  //^ <T as Foo<i32>>::Assoc<usize>
+}
+"#,
+    );
+}
+
+#[test]
+fn generic_associated_type_binding_in_impl_trait() {
+    check_types_source_code(
+        r#"
+//- minicore: sized
+trait Foo<T> {
+    type Assoc<U>;
+}
+fn f(a: impl Foo<i8, Assoc<i16> = i32>) {
+    a;
+  //^ impl Foo<i8, Assoc<i16> = i32>
+}
+        "#,
+    );
+}
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/tests/method_resolution.rs b/src/tools/rust-analyzer/crates/hir-ty/src/tests/method_resolution.rs
index ac8edb841..5d76d185f 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/tests/method_resolution.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/tests/method_resolution.rs
@@ -164,16 +164,16 @@ fn infer_associated_method_with_modules() {
     check_infer(
         r#"
         mod a {
-            struct A;
+            pub struct A;
             impl A { pub fn thing() -> A { A {} }}
         }
 
         mod b {
-            struct B;
+            pub struct B;
             impl B { pub fn thing() -> u32 { 99 }}
 
-            mod c {
-                struct C;
+            pub mod c {
+                pub struct C;
                 impl C { pub fn thing() -> C { C {} }}
             }
         }
@@ -186,22 +186,22 @@ fn infer_associated_method_with_modules() {
         }
         "#,
         expect![[r#"
-            55..63 '{ A {} }': A
-            57..61 'A {}': A
-            125..131 '{ 99 }': u32
-            127..129 '99': u32
-            201..209 '{ C {} }': C
-            203..207 'C {}': C
-            240..324 '{     ...g(); }': ()
-            250..251 'x': A
-            254..265 'a::A::thing': fn thing() -> A
-            254..267 'a::A::thing()': A
-            277..278 'y': u32
-            281..292 'b::B::thing': fn thing() -> u32
-            281..294 'b::B::thing()': u32
-            304..305 'z': C
-            308..319 'c::C::thing': fn thing() -> C
-            308..321 'c::C::thing()': C
+            59..67 '{ A {} }': A
+            61..65 'A {}': A
+            133..139 '{ 99 }': u32
+            135..137 '99': u32
+            217..225 '{ C {} }': C
+            219..223 'C {}': C
+            256..340 '{     ...g(); }': ()
+            266..267 'x': A
+            270..281 'a::A::thing': fn thing() -> A
+            270..283 'a::A::thing()': A
+            293..294 'y': u32
+            297..308 'b::B::thing': fn thing() -> u32
+            297..310 'b::B::thing()': u32
+            320..321 'z': C
+            324..335 'c::C::thing': fn thing() -> C
+            324..337 'c::C::thing()': C
         "#]],
     );
 }
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/tests/regression.rs b/src/tools/rust-analyzer/crates/hir-ty/src/tests/regression.rs
index a155adcec..4e4639745 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/tests/regression.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/tests/regression.rs
@@ -1707,3 +1707,19 @@ impl<T, const N: usize> Trait for [T; N] {
         "#,
     );
 }
+
+#[test]
+fn unsize_array_with_inference_variable() {
+    check_types(
+        r#"
+//- minicore: try, slice
+use core::ops::ControlFlow;
+fn foo() -> ControlFlow<(), [usize; 1]> { loop {} }
+fn bar() -> ControlFlow<(), ()> {
+    let a = foo()?.len();
+      //^ usize
+    ControlFlow::Continue(())
+}
+"#,
+    );
+}
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/tests/simple.rs b/src/tools/rust-analyzer/crates/hir-ty/src/tests/simple.rs
index 080e2ac1b..d7431443b 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/tests/simple.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/tests/simple.rs
@@ -214,7 +214,7 @@ fn infer_paths() {
 fn a() -> u32 { 1 }
 
 mod b {
-    fn c() -> u32 { 1 }
+    pub fn c() -> u32 { 1 }
 }
 
 fn test() {
@@ -225,13 +225,13 @@ fn test() {
         expect![[r#"
             14..19 '{ 1 }': u32
             16..17 '1': u32
-            47..52 '{ 1 }': u32
-            49..50 '1': u32
-            66..90 '{     ...c(); }': ()
-            72..73 'a': fn a() -> u32
-            72..75 'a()': u32
-            81..85 'b::c': fn c() -> u32
-            81..87 'b::c()': u32
+            51..56 '{ 1 }': u32
+            53..54 '1': u32
+            70..94 '{     ...c(); }': ()
+            76..77 'a': fn a() -> u32
+            76..79 'a()': u32
+            85..89 'b::c': fn c() -> u32
+            85..91 'b::c()': u32
         "#]],
     );
 }
@@ -1856,7 +1856,7 @@ fn not_shadowing_module_by_primitive() {
     check_types(
         r#"
 //- /str.rs
-fn foo() -> u32 {0}
+pub fn foo() -> u32 {0}
 
 //- /main.rs
 mod str;
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/tests/traits.rs b/src/tools/rust-analyzer/crates/hir-ty/src/tests/traits.rs
index 555b6972f..3d7194b6f 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/tests/traits.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/tests/traits.rs
@@ -1706,7 +1706,7 @@ fn where_clause_trait_in_scope_for_method_resolution() {
     check_types(
         r#"
 mod foo {
-    trait Trait {
+    pub trait Trait {
         fn foo(&self) -> u32 { 0 }
     }
 }
@@ -1723,7 +1723,7 @@ fn super_trait_method_resolution() {
     check_infer(
         r#"
 mod foo {
-    trait SuperTrait {
+    pub trait SuperTrait {
         fn foo(&self) -> u32 {}
     }
 }
@@ -1735,15 +1735,15 @@ fn test<T: Trait1, U: Trait2>(x: T, y: U) {
     y.foo();
 }"#,
         expect![[r#"
-            49..53 'self': &Self
-            62..64 '{}': u32
-            181..182 'x': T
-            187..188 'y': U
-            193..222 '{     ...o(); }': ()
-            199..200 'x': T
-            199..206 'x.foo()': u32
-            212..213 'y': U
-            212..219 'y.foo()': u32
+            53..57 'self': &Self
+            66..68 '{}': u32
+            185..186 'x': T
+            191..192 'y': U
+            197..226 '{     ...o(); }': ()
+            203..204 'x': T
+            203..210 'x.foo()': u32
+            216..217 'y': U
+            216..223 'y.foo()': u32
         "#]],
     );
 }
@@ -1754,7 +1754,7 @@ fn super_trait_impl_trait_method_resolution() {
         r#"
 //- minicore: sized
 mod foo {
-    trait SuperTrait {
+    pub trait SuperTrait {
         fn foo(&self) -> u32 {}
     }
 }
@@ -1764,12 +1764,12 @@ fn test(x: &impl Trait1) {
     x.foo();
 }"#,
         expect![[r#"
-            49..53 'self': &Self
-            62..64 '{}': u32
-            115..116 'x': &impl Trait1
-            132..148 '{     ...o(); }': ()
-            138..139 'x': &impl Trait1
-            138..145 'x.foo()': u32
+            53..57 'self': &Self
+            66..68 '{}': u32
+            119..120 'x': &impl Trait1
+            136..152 '{     ...o(); }': ()
+            142..143 'x': &impl Trait1
+            142..149 'x.foo()': u32
         "#]],
     );
 }
@@ -3963,3 +3963,124 @@ fn g(t: &(dyn T + Send)) {
         "#,
     );
 }
+
+#[test]
+fn gats_in_path() {
+    check_types(
+        r#"
+//- minicore: deref
+use core::ops::Deref;
+trait PointerFamily {
+    type Pointer<T>: Deref<Target = T>;
+}
+
+fn f<P: PointerFamily>(p: P::Pointer<i32>) {
+    let a = *p;
+      //^ i32
+}
+fn g<P: PointerFamily>(p: <P as PointerFamily>::Pointer<i32>) {
+    let a = *p;
+      //^ i32
+}
+        "#,
+    );
+}
+
+#[test]
+fn gats_with_impl_trait() {
+    // FIXME: the last function (`fn i()`) is not valid Rust as of this writing because you cannot
+    // specify the same associated type multiple times even if their arguments are different (c.f.
+    // `fn h()`, which is valid). Reconsider how to treat these invalid types.
+    check_types(
+        r#"
+//- minicore: deref
+use core::ops::Deref;
+
+trait Trait {
+    type Assoc<T>: Deref<Target = T>;
+    fn get<U>(&self) -> Self::Assoc<U>;
+}
+
+fn f<T>(v: impl Trait) {
+    let a = v.get::<i32>().deref();
+      //^ &i32
+    let a = v.get::<T>().deref();
+      //^ &T
+}
+fn g<'a, T: 'a>(v: impl Trait<Assoc<T> = &'a T>) {
+    let a = v.get::<T>();
+      //^ &T
+    let a = v.get::<()>();
+      //^ Trait::Assoc<(), impl Trait<Assoc<T> = &T>>
+}
+fn h<'a>(v: impl Trait<Assoc<i32> = &'a i32> + Trait<Assoc<i64> = &'a i64>) {
+    let a = v.get::<i32>();
+      //^ &i32
+    let a = v.get::<i64>();
+      //^ &i64
+}
+fn i<'a>(v: impl Trait<Assoc<i32> = &'a i32, Assoc<i64> = &'a i64>) {
+    let a = v.get::<i32>();
+      //^ &i32
+    let a = v.get::<i64>();
+      //^ &i64
+}
+    "#,
+    );
+}
+
+#[test]
+fn gats_with_dyn() {
+    // This test is here to keep track of how we infer things despite traits with GATs being not
+    // object-safe currently.
+    // FIXME: reconsider how to treat these invalid types.
+    check_infer_with_mismatches(
+        r#"
+//- minicore: deref
+use core::ops::Deref;
+
+trait Trait {
+    type Assoc<T>: Deref<Target = T>;
+    fn get<U>(&self) -> Self::Assoc<U>;
+}
+
+fn f<'a>(v: &dyn Trait<Assoc<i32> = &'a i32>) {
+    v.get::<i32>().deref();
+}
+    "#,
+        expect![[r#"
+            90..94 'self': &Self
+            127..128 'v': &(dyn Trait<Assoc<i32> = &i32>)
+            164..195 '{     ...f(); }': ()
+            170..171 'v': &(dyn Trait<Assoc<i32> = &i32>)
+            170..184 'v.get::<i32>()': &i32
+            170..192 'v.get:...eref()': &i32
+        "#]],
+    );
+}
+
+#[test]
+fn gats_in_associated_type_binding() {
+    check_types(
+        r#"
+trait Trait {
+    type Assoc<T>;
+    fn get<U>(&self) -> Self::Assoc<U>;
+}
+
+fn f<T>(t: T)
+where
+    T: Trait<Assoc<i32> = u32>,
+    T: Trait<Assoc<isize> = usize>,
+{
+    let a = t.get::<i32>();
+      //^ u32
+    let a = t.get::<isize>();
+      //^ usize
+    let a = t.get::<()>();
+      //^ Trait::Assoc<(), T>
+}
+
+    "#,
+    );
+}
diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/tls.rs b/src/tools/rust-analyzer/crates/hir-ty/src/tls.rs
index 547850b02..92711a24f 100644
--- a/src/tools/rust-analyzer/crates/hir-ty/src/tls.rs
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/tls.rs
@@ -5,7 +5,7 @@ use itertools::Itertools;
 
 use crate::{
     chalk_db, db::HirDatabase, from_assoc_type_id, from_chalk_trait_id, mapping::from_chalk,
-    CallableDefId, Interner,
+    CallableDefId, Interner, ProjectionTyExt,
 };
 use hir_def::{AdtId, ItemContainerId, Lookup, TypeAliasId};
 
@@ -63,17 +63,31 @@ impl DebugContext<'_> {
             ItemContainerId::TraitId(t) => t,
             _ => panic!("associated type not in trait"),
         };
-        let trait_data = self.0.trait_data(trait_);
-        let params = projection_ty.substitution.as_slice(Interner);
-        write!(fmt, "<{:?} as {}", &params[0], trait_data.name,)?;
-        if params.len() > 1 {
+        let trait_name = &self.0.trait_data(trait_).name;
+        let trait_ref = projection_ty.trait_ref(self.0);
+        let trait_params = trait_ref.substitution.as_slice(Interner);
+        let self_ty = trait_ref.self_type_parameter(Interner);
+        write!(fmt, "<{:?} as {}", self_ty, trait_name)?;
+        if trait_params.len() > 1 {
+            write!(
+                fmt,
+                "<{}>",
+                trait_params[1..].iter().format_with(", ", |x, f| f(&format_args!("{:?}", x))),
+            )?;
+        }
+        write!(fmt, ">::{}", type_alias_data.name)?;
+
+        let proj_params_count = projection_ty.substitution.len(Interner) - trait_params.len();
+        let proj_params = &projection_ty.substitution.as_slice(Interner)[..proj_params_count];
+        if !proj_params.is_empty() {
             write!(
                 fmt,
                 "<{}>",
-                &params[1..].iter().format_with(", ", |x, f| f(&format_args!("{:?}", x))),
+                proj_params.iter().format_with(", ", |x, f| f(&format_args!("{:?}", x))),
             )?;
         }
-        write!(fmt, ">::{}", type_alias_data.name)
+
+        Ok(())
     }
 
     pub(crate) fn debug_fn_def_id(