4 files changed, 16 insertions, 11 deletions

diff --git a/crates/ra_hir/Cargo.toml b/crates/ra_hir/Cargo.toml
index 5a8fdbfc6..0135e0e16 100644
--- a/crates/ra_hir/Cargo.toml
+++ b/crates/ra_hir/Cargo.toml
@@ -12,6 +12,7 @@ salsa = "0.9.1"
 rustc-hash = "1.0"
 parking_lot = "0.7.0"
 ena = "0.11"
+join_to_string = "0.1.3"
 ra_syntax = { path = "../ra_syntax" }
 ra_arena = { path = "../ra_arena" }
 ra_db = { path = "../ra_db" }
diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index 3b2bfd67a..eb7764f65 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -25,6 +25,7 @@ use std::{fmt, mem};
 use log;
 use ena::unify::{InPlaceUnificationTable, UnifyKey, UnifyValue, NoError};
 use ra_arena::map::ArenaMap;
+use join_to_string::join;
 
 use ra_db::Cancelable;
 
@@ -396,18 +397,21 @@ impl fmt::Display for Ty {
             Ty::Ref(t, m) => write!(f, "&{}{}", m.as_keyword_for_ref(), t),
             Ty::Never => write!(f, "!"),
             Ty::Tuple(ts) => {
-                write!(f, "(")?;
-                for t in ts.iter() {
-                    write!(f, "{},", t)?;
+                if ts.len() == 1 {
+                    write!(f, "({},)", ts[0])
+                } else {
+                    join(ts.iter())
+                        .surround_with("(", ")")
+                        .separator(", ")
+                        .to_fmt(f)
                 }
-                write!(f, ")")
             }
             Ty::FnPtr(sig) => {
-                write!(f, "fn(")?;
-                for t in &sig.input {
-                    write!(f, "{},", t)?;
-                }
-                write!(f, ") -> {}", sig.output)
+                join(sig.input.iter())
+                    .surround_with("fn(", ")")
+                    .separator(", ")
+                    .to_fmt(f)?;
+                write!(f, " -> {}", sig.output)
             }
             Ty::Adt { name, .. } => write!(f, "{}", name),
             Ty::Unknown => write!(f, "[unknown]"),
diff --git a/crates/ra_hir/src/ty/tests/data/backwards.txt b/crates/ra_hir/src/ty/tests/data/backwards.txt
index b6807fb2a..b8593cfd1 100644
--- a/crates/ra_hir/src/ty/tests/data/backwards.txt
+++ b/crates/ra_hir/src/ty/tests/data/backwards.txt
@@ -4,7 +4,7 @@
 [88; 89) 'a': u32
 [92; 108) 'unknow...nction': [unknown]
 [92; 110) 'unknow...tion()': u32
-[116; 125) 'takes_u32': fn(u32,) -> ()
+[116; 125) 'takes_u32': fn(u32) -> ()
 [116; 128) 'takes_u32(a)': ()
 [126; 127) 'a': u32
 [138; 139) 'b': i32
diff --git a/crates/ra_hir/src/ty/tests/data/binary_op.txt b/crates/ra_hir/src/ty/tests/data/binary_op.txt
index 0fb9dc097..8a515ac5e 100644
--- a/crates/ra_hir/src/ty/tests/data/binary_op.txt
+++ b/crates/ra_hir/src/ty/tests/data/binary_op.txt
@@ -22,7 +22,7 @@
 [166; 188) 'minus_...ONST_2': bool
 [181; 188) 'CONST_2': isize
 [198; 199) 'c': i32
-[202; 203) 'f': fn(bool,) -> i32
+[202; 203) 'f': fn(bool) -> i32
 [202; 211) 'f(z || y)': i32
 [202; 215) 'f(z || y) + 5': i32
 [204; 205) 'z': bool