From 4d9fa00fd58373f4ee19b6a45ab37e4601a8dd93 Mon Sep 17 00:00:00 2001
From: Caleb Cartwright <caleb.cartwright@outlook.com>
Date: Fri, 27 Nov 2020 21:18:39 -0600
Subject: [PATCH] feat: support underscore expressions

---
 src/expr.rs          |  1 +
 src/utils.rs         |  3 ++-
 tests/source/expr.rs | 10 ++++++++++
 tests/target/expr.rs | 10 ++++++++++
 4 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/expr.rs b/src/expr.rs
index 38543b70ae3..fe348bc6028 100644
--- a/src/expr.rs
+++ b/src/expr.rs
@@ -384,6 +384,7 @@ pub(crate) fn format_expr(
             }
         }
         ast::ExprKind::Await(_) => rewrite_chain(expr, context, shape),
+        ast::ExprKind::Underscore => Some("_".to_owned()),
         ast::ExprKind::Err => None,
     };
 
diff --git a/src/utils.rs b/src/utils.rs
index 96d465608fa..bd419b2998b 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -504,7 +504,8 @@ pub(crate) fn is_block_expr(context: &RewriteContext<'_>, expr: &ast::Expr, repr
         | ast::ExprKind::Ret(..)
         | ast::ExprKind::Tup(..)
         | ast::ExprKind::Type(..)
-        | ast::ExprKind::Yield(None) => false,
+        | ast::ExprKind::Yield(None)
+        | ast::ExprKind::Underscore => false,
     }
 }
 
diff --git a/tests/source/expr.rs b/tests/source/expr.rs
index 8a6e6f1aa2b..21f8a4a4366 100644
--- a/tests/source/expr.rs
+++ b/tests/source/expr.rs
@@ -567,3 +567,13 @@ fn foo() {
     }
         .await;
 }
+
+fn underscore() {
+        _= 1;
+        _;
+        [  _,a,_  ] = [1, 2, 3];
+    (a,   _) = (8, 9);
+    TupleStruct(  _, a) = TupleStruct(2, 2);
+
+    let _  : usize = foo(_, _);
+}
diff --git a/tests/target/expr.rs b/tests/target/expr.rs
index 5d9e972066c..84df802bc70 100644
--- a/tests/target/expr.rs
+++ b/tests/target/expr.rs
@@ -659,3 +659,13 @@ fn foo() {
     }
     .await;
 }
+
+fn underscore() {
+    _ = 1;
+    _;
+    [_, a, _] = [1, 2, 3];
+    (a, _) = (8, 9);
+    TupleStruct(_, a) = TupleStruct(2, 2);
+
+    let _: usize = foo(_, _);
+}