3 files changed, 12 insertions, 8 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 975c1aef8..c2779afc2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1013,6 +1013,7 @@ dependencies = [
  "chalk-solve",
  "ena",
  "insta",
+ "itertools",
  "log",
  "ra_arena",
  "ra_db",
diff --git a/crates/ra_hir_ty/Cargo.toml b/crates/ra_hir_ty/Cargo.toml
index 59efc1c31..c863112c0 100644
--- a/crates/ra_hir_ty/Cargo.toml
+++ b/crates/ra_hir_ty/Cargo.toml
@@ -8,6 +8,7 @@ authors = ["rust-analyzer developers"]
 doctest = false
 
 [dependencies]
+itertools = "0.9.0"
 arrayvec = "0.5.1"
 smallvec = "1.2.0"
 ena = "0.13.1"
diff --git a/crates/ra_hir_ty/src/traits/chalk/tls.rs b/crates/ra_hir_ty/src/traits/chalk/tls.rs
index 0a8932dae..fa8e4d1ad 100644
--- a/crates/ra_hir_ty/src/traits/chalk/tls.rs
+++ b/crates/ra_hir_ty/src/traits/chalk/tls.rs
@@ -2,6 +2,7 @@
 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};
@@ -133,14 +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(