ast: Make struct formatting look cool

src/ast.rs

@@ -127,7 +127,6 @@ pub struct Mod<A: Annotation = Span>(pub Ty, pub Anno<Expr<A>, A>);
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct Struct(pub Pat);
 
-
 /// Expressions: The beating heart of Dough
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum Expr<A: Annotation = Span> {
@@ -312,7 +311,15 @@ impl<A: Annotation> Display for Mod<A> {
 impl Display for Struct {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let Self(pat) = self;
-        write!(f, "struct {pat}")
+        match pat {
+            Pat::Struct(name, bind) => match bind.as_ref() {
+                Pat::Tuple(parts) => f
+                    .delimit_indented(fmt!("{name} {{"), "}")
+                    .list_wrap("\n", parts, ",\n", ",\n"),
+                other => write!(f, "{name} {{ {other} }}"),
+            },
+            _ => write!(f, "struct {pat}"),
+        }
     }
 }
 
@@ -438,7 +445,10 @@ impl Display for Pat {
             Self::Lit(literal) => literal.fmt(f),
             Self::MetId(name) => write!(f, "`{name}"),
             Self::Name(name) => name.fmt(f),
-            Self::Struct(name, bind) => write!(f, "{name} {{{bind}}}"),
+            Self::Struct(name, bind) => match bind.as_ref() {
+                Pat::Tuple(parts) => f.delimit(fmt!("{name} {{"), "}").list(parts, ", "),
+                other => write!(f, "{name} {{ {other} }}"),
+            },
             Self::TupStruct(name, bind) => write!(f, "{name} {bind}"),
             Self::Rest(Some(rest)) => write!(f, "..{rest}"),
             Self::Rest(None) => write!(f, ".."),