fix(compiler): Improve error message for impl on primitive types (#10430)

compiler/noirc_frontend/src/elaborator/impls.rs

@@ -210,7 +210,11 @@ impl Elaborator<'_> {
                     self.declare_methods(self_type, &function_ids);
                 }
             } else {
-                self.push_err(DefCollectorErrorKind::NonStructTypeInImpl { location });
+                let is_primitive = self_type.is_primitive();
+                self.push_err(DefCollectorErrorKind::NonStructTypeInImpl {
+                    location,
+                    is_primitive,
+                });
             }
         }
     }

compiler/noirc_frontend/src/hir/def_collector/errors.rs

@@ -35,7 +35,7 @@ pub enum DefCollectorErrorKind {
     #[error("Cannot re-export {item_name} because it has less visibility than this use statement")]
     CannotReexportItemWithLessVisibility { item_name: Ident, desired_visibility: ItemVisibility },
     #[error("Non-struct type used in impl")]
-    NonStructTypeInImpl { location: Location },
+    NonStructTypeInImpl { location: Location, is_primitive: bool },
     #[error("Cannot implement trait on a reference type")]
     ReferenceInTraitImpl { location: Location },
     #[error("Impl for type `{typ}` overlaps with existing impl")]
@@ -101,7 +101,7 @@ impl DefCollectorErrorKind {
             }
             | DefCollectorErrorKind::TestOnAssociatedFunction { location }
             | DefCollectorErrorKind::ExportOnAssociatedFunction { location }
-            | DefCollectorErrorKind::NonStructTypeInImpl { location }
+            | DefCollectorErrorKind::NonStructTypeInImpl { location, .. }
             | DefCollectorErrorKind::ReferenceInTraitImpl { location }
             | DefCollectorErrorKind::OverlappingImpl { location, .. }
             | DefCollectorErrorKind::ModuleAlreadyPartOfCrate { location, .. }
@@ -193,11 +193,21 @@ impl<'a> From<&'a DefCollectorErrorKind> for Diagnostic {
                     format!("consider marking {item_name} as {desired_visibility}"),
                     item_name.location())
             }
-            DefCollectorErrorKind::NonStructTypeInImpl { location } => Diagnostic::simple_error(
-                "Non-struct type used in impl".into(),
-                "Only struct types may have implementation methods".into(),
-                *location,
-            ),
+            DefCollectorErrorKind::NonStructTypeInImpl { location, is_primitive } =>{
+                if *is_primitive {
+                    Diagnostic::simple_error(
+                        "Cannot define inherent `impl` for primitive types".into(),
+                        "Primitive types can only have implementation methods defined in the standard library".into(),
+                        *location,
+                    )
+                }else{
+                    Diagnostic::simple_error(
+                        "Non-struct type used in impl".into(),
+                        "Only struct types may have implementation methods".into(),
+                        *location,
+                    )
+                }
+            }
             DefCollectorErrorKind::ReferenceInTraitImpl { location } => Diagnostic::simple_error(
                 "Trait impls are not allowed on reference types".into(),
                 "Try using a struct type here instead".into(),

compiler/noirc_frontend/src/tests/structs.rs

@@ -222,8 +222,8 @@ fn errors_on_impl_for_primitive_type_outside_stdlib() {
     let src = r#"
     // User code (not stdlib) cannot impl methods on primitive types
     impl Field {
-         ^^^^^ Non-struct type used in impl
-         ~~~~~ Only struct types may have implementation methods
+         ^^^^^ Cannot define inherent `impl` for primitive types
+         ~~~~~ Primitive types can only have implementation methods defined in the standard library
         fn my_method(self) -> Field {
             self
         }