Implement ADT contracts

cli/tests/snapshot/inputs/errors/enum_contract_shape_mismatch.ncl

@@ -0,0 +1,3 @@
+# capture = 'stderr'
+# command = ['eval']
+(std.function.id | forall r. [| 'Foo Number, 'Bar String, 'Qux; r |] -> [| 'Foo Number, 'Bar String, 'Qux; r |]) 'Foo

cli/tests/snapshot/inputs/errors/enum_contract_shape_mismatch_rev.ncl

@@ -0,0 +1,3 @@
+# capture = 'stderr'
+# command = ['eval']
+(std.function.id | forall r. [| 'Foo, 'Bar String, 'Qux Dyn; r |] -> [| 'Foo, 'Bar String, 'Qux Dyn; r |]) ('Foo..(5))

cli/tests/snapshot/snapshots/snapshot__eval_stderr_enum_contract_shape_mismatch.ncl.snap

@@ -0,0 +1,29 @@
+---
+source: cli/tests/snapshot/main.rs
+expression: err
+---
+error: contract broken by the caller
+       shape mismatch for 'Foo
+  ┌─ [INPUTS_PATH]/errors/enum_contract_shape_mismatch.ncl:3:30
+  │
+3 │ (std.function.id | forall r. [| 'Foo Number, 'Bar String, 'Qux; r |] -> [| 'Foo Number, 'Bar String, 'Qux; r |]) 'Foo
+  │                              ---------------------------------------                                             ---- evaluated to this expression
+  │                              │                                                                                    
+  │                              expected type of the argument provided by the caller
+  │
+  = Found an enum with tag `'Foo` which is indeed part of the expected enum type
+  = However, their shape differs: one is an enum variant that carries an argument while the other is a bare enum tag
+
+note: 
+  ┌─ [INPUTS_PATH]/errors/enum_contract_shape_mismatch.ncl:3:1
+  │
+3 │ (std.function.id | forall r. [| 'Foo Number, 'Bar String, 'Qux; r |] -> [| 'Foo Number, 'Bar String, 'Qux; r |]) 'Foo
+  │ --------------------------------------------------------------------------------------------------------------------- (1) calling <func>
+
+note: 
+  ┌─ [INPUTS_PATH]/errors/enum_contract_shape_mismatch.ncl:3:2
+  │
+3 │ (std.function.id | forall r. [| 'Foo Number, 'Bar String, 'Qux; r |] -> [| 'Foo Number, 'Bar String, 'Qux; r |]) 'Foo
+  │  --------------- (2) calling <func>
+
+

cli/tests/snapshot/snapshots/snapshot__eval_stderr_enum_contract_shape_mismatch_rev.ncl.snap

@@ -0,0 +1,29 @@
+---
+source: cli/tests/snapshot/main.rs
+expression: err
+---
+error: contract broken by the caller
+       shape mismatch for 'Foo
+  ┌─ [INPUTS_PATH]/errors/enum_contract_shape_mismatch_rev.ncl:3:30
+  │
+3 │ (std.function.id | forall r. [| 'Foo, 'Bar String, 'Qux Dyn; r |] -> [| 'Foo, 'Bar String, 'Qux Dyn; r |]) ('Foo..(5))
+  │                              ------------------------------------                                          ----------- evaluated to this expression
+  │                              │                                                                              
+  │                              expected type of the argument provided by the caller
+  │
+  = Found an enum with tag `'Foo` which is indeed part of the expected enum type
+  = However, their shape differs: one is an enum variant that carries an argument while the other is a bare enum tag
+
+note: 
+  ┌─ [INPUTS_PATH]/errors/enum_contract_shape_mismatch_rev.ncl:3:1
+  │
+3 │ (std.function.id | forall r. [| 'Foo, 'Bar String, 'Qux Dyn; r |] -> [| 'Foo, 'Bar String, 'Qux Dyn; r |]) ('Foo..(5))
+  │ ---------------------------------------------------------------------------------------------------------------------- (1) calling <func>
+
+note: 
+  ┌─ [INPUTS_PATH]/errors/enum_contract_shape_mismatch_rev.ncl:3:2
+  │
+3 │ (std.function.id | forall r. [| 'Foo, 'Bar String, 'Qux Dyn; r |] -> [| 'Foo, 'Bar String, 'Qux Dyn; r |]) ('Foo..(5))
+  │  --------------- (2) calling <func>
+
+

core/src/eval/operation.rs

@@ -2300,7 +2300,7 @@ impl<R: ImportResolver, C: Cache> VirtualMachine<R, C> {
                 let Term::Array(array, _) = t1 else {
                     return Err(mk_type_error!(
                         "label_with_notes",
-                        "Array String",
+                        "Array",
                         1,
                         t1.into(),
                         pos1

core/src/stdlib.rs

@@ -64,29 +64,41 @@ pub mod internals {
         mk_term::var("$dyn")
     }
 
+    // `enum` is a reserved keyword in rust
+    pub fn enumeration() -> RichTerm {
+        mk_term::var("$enum")
+    }
+
     generate_accessor!(num);
     generate_accessor!(bool);
     generate_accessor!(string);
+    generate_accessor!(fail);
+
     generate_accessor!(array);
     generate_accessor!(array_dyn);
+
     generate_accessor!(func);
     generate_accessor!(func_dom);
     generate_accessor!(func_codom);
     generate_accessor!(func_dyn);
+
     generate_accessor!(forall_var);
     generate_accessor!(forall);
-    generate_accessor!(fail);
-    generate_accessor!(enums);
+
     generate_accessor!(enum_fail);
+    generate_accessor!(enum_variant);
+    generate_accessor!(forall_enum_tail);
+
     generate_accessor!(record);
-    generate_accessor!(dict_type);
-    generate_accessor!(dict_contract);
-    generate_accessor!(dict_dyn);
     generate_accessor!(record_extend);
-    generate_accessor!(forall_tail);
+    generate_accessor!(forall_record_tail);
     generate_accessor!(dyn_tail);
     generate_accessor!(empty_tail);
-    generate_accessor!(enum_variant);
+
+    generate_accessor!(dict_type);
+    generate_accessor!(dict_contract);
+    generate_accessor!(dict_dyn);
+
     generate_accessor!(stdlib_contract_equal);
 
     generate_accessor!(rec_default);