respect alternative flag

Author: nikomatsakis

crates/formality-core/src/binder.rs

@@ -261,17 +261,24 @@ where
     T: std::fmt::Debug,
 {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        if !self.kinds.is_empty() {
-            write!(f, "{}", L::BINDING_OPEN)?;
-            for (kind, i) in self.kinds.iter().zip(0..) {
-                if i > 0 {
-                    write!(f, ", ")?;
+        if f.alternate() {
+            f.debug_struct("Binder")
+                .field("kinds", &self.kinds)
+                .field("term", &self.term)
+                .finish()
+        } else {
+            if !self.kinds.is_empty() {
+                write!(f, "{}", L::BINDING_OPEN)?;
+                for (kind, i) in self.kinds.iter().zip(0..) {
+                    if i > 0 {
+                        write!(f, ", ")?;
+                    }
+                    write!(f, "{:?}", kind)?;
                 }
-                write!(f, "{:?}", kind)?;
+                write!(f, "{} ", L::BINDING_CLOSE)?;
             }
-            write!(f, "{} ", L::BINDING_CLOSE)?;
+            write!(f, "{:?}", &self.term)?;
+            Ok(())
         }
-        write!(f, "{:?}", &self.term)?;
-        Ok(())
     }
 }

examples/formality-eg/grammar/test.rs

@@ -10,7 +10,21 @@ fn test_struct_decl() {
     expect_test::expect![[r#"
         StructDecl {
             id: Point,
-            bound: { x : integer, y : integer },
+            bound: Binder {
+                kinds: [],
+                term: StructBoundData {
+                    fields: [
+                        FieldDecl {
+                            name: x,
+                            ty: Integer,
+                        },
+                        FieldDecl {
+                            name: y,
+                            ty: Integer,
+                        },
+                    ],
+                },
+            },
         }
     "#]]
     .assert_debug_eq(&r);