Correctly surround binop sides with {} if required

Closes #618

Author: lpil

CHANGELOG.md

@@ -5,6 +5,8 @@
 - Newly generated projects use stdlib v0.9.0.
 - Additional information is printed to the console when generating HTML
   documentation from Gleam code.
+- Fixed a bug where blocks on either side of a binary operator would be
+  rendered without `{ }`.
 
 ## v0.9.0-rc1 - 2020-05-26
 

src/format.rs

@@ -572,7 +572,7 @@ impl<'a> Formatter<'a> {
     fn pipe(&mut self, left: &UntypedExpr, right: &UntypedExpr, location_start: usize) -> Document {
         let left_precedence = left.binop_precedence();
         let right_precedence = right.binop_precedence();
-        let left = self.expr(left);
+        let left = self.wrap_expr(left);
 
         // Get comments before right but after left
         let comments = self.pop_comments(location_start);
@@ -584,7 +584,7 @@ impl<'a> Formatter<'a> {
                 ..
             } => self.pipe_capture_right_hand_side(body),
 
-            _ => self.expr(right),
+            _ => self.wrap_expr(right),
         };
 
         // Wrap sides if required

src/format/tests.rs

@@ -1148,6 +1148,30 @@ World"
 "#
     );
 
+    // https://github.com/gleam-lang/gleam/issues/618
+
+    assert_format!(
+        r#"fn main() {
+  {
+    1
+    2
+  }
+  |> func
+}
+"#
+    );
+
+    assert_format!(
+        r#"fn main() {
+  1
+  |> {
+    1
+    2
+  }
+}
+"#
+    );
+
     //
     // Let
     //