Improved error messages for possible function callees that have polym…

…orphic arguments with constraints

src/resolve/type_ctx/mod.rs

@@ -9,7 +9,7 @@ use super::{
 use crate::{
     ast,
     name::ResolvedName,
-    resolved::{self, Constraint, CurrentConstraints},
+    resolved::{self, Constraint, CurrentConstraints, HumanName},
     workspace::fs::FsNodeId,
 };
 use std::collections::{HashMap, HashSet};
@@ -91,7 +91,7 @@ pub fn resolve_constraint(
                     .at(resolved_type.source));
                 };
 
-                return Ok(Constraint::Trait(*trait_ref));
+                return Ok(Constraint::Trait(HumanName(name.to_string()), *trait_ref));
             }
         }
     }

src/resolved/datatype/kind/constraint.rs

@@ -1,17 +1,25 @@
-use crate::resolved::TraitRef;
+use crate::resolved::{HumanName, TraitRef};
+use derivative::Derivative;
+use derive_more::IsVariant;
 use std::fmt::Display;
 
-#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+#[derive(Clone, Debug, IsVariant, Derivative)]
+#[derivative(PartialEq, Eq, Hash)]
 pub enum Constraint {
     PrimitiveAdd,
-    Trait(TraitRef),
+    Trait(
+        #[derivative(PartialEq = "ignore")]
+        #[derivative(Hash = "ignore")]
+        HumanName,
+        TraitRef,
+    ),
 }
 
 impl Display for Constraint {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
             Constraint::PrimitiveAdd => write!(f, "PrimitiveAdd"),
-            Constraint::Trait(_) => write!(f, "<user-defined trait>"),
+            Constraint::Trait(name, _) => write!(f, "{}", name),
         }
     }
 }

src/resolved/datatype/kind/mod.rs

@@ -190,7 +190,7 @@ impl Display for TypeKind {
                 }
 
                 for constaint in constaints {
-                    write!(f, "{:?}", constaint)?;
+                    write!(f, "{}", constaint)?;
                 }
             }
             TypeKind::Trait(name, _) => {