Add the package std module

cli/src/doctest.rs

@@ -181,7 +181,7 @@ fn run_tests(
                     let _ = std::io::stdout().flush();
 
                     // Undo the test's lazy wrapper.
-                    let result = prog.eval_closure(Closure {
+                    let result = prog.eval_deep_closure(Closure {
                         body: mk_app!(val.clone(), Term::Null),
                         env: Environment::new(),
                     });

cli/tests/snapshot/inputs/doctest/fail_unexpected_error.ncl

@@ -3,14 +3,22 @@
 {
   foo
     | doc m%"
-    ```nickel
-    foo + "1"
-    ```
+      ```nickel
+      foo + "1"
+      ```
 
-    ```nickel
-    foo + "1"
-    # => 2
-    ```
+      ```nickel
+      foo + "1"
+      # => 2
+      ```
     "%
     = 1,
+
+  bar
+    | doc m%"
+      ```nickel
+      { foo = 1 }
+      # => { foo = 2 }
+      ```
+    "%
 }

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

@@ -2,5 +2,5 @@
 source: cli/tests/snapshot/main.rs
 expression: err
 ---
-2 failures
+3 failures
 error: tests failed

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

@@ -4,6 +4,7 @@ expression: out
 ---
 testing foo/0...FAILED
 testing foo/1...FAILED
+testing bar/0...FAILED
 test foo/0 failed
 error: dynamic type error
   ┌─ [INPUTS_PATH]/doctest/fail_unexpected_error.ncl:1:7
@@ -21,3 +22,15 @@ error: dynamic type error
   │       ^^^ this expression has type String, but Number was expected
   │
   = (+) expects its 2nd argument to be a Number
+
+test bar/0 failed
+error: contract broken by a value
+  ┌─ <unknown> (generated by evaluation):1:1
+  │
+1 │ std.contract.Equal { foo = 2, }
+  │ ------------------------------- expected type
+  │
+  ┌─ [INPUTS_PATH]/doctest/fail_unexpected_error.ncl:1:9
+  │
+1 │ { foo = 1 }
+  │         ^ applied to this expression

core/src/program.rs

@@ -553,6 +553,14 @@ impl<EC: EvalCache> Program<EC> {
         Ok(self.vm.eval_deep_closure(prepared)?)
     }
 
+    /// Same as `eval_closure`, but does a full evaluation and does not substitute all variables.
+    ///
+    /// (Or, same as `eval_deep` but takes a closure.)
+    pub fn eval_deep_closure(&mut self, closure: Closure) -> Result<RichTerm, EvalError> {
+        self.vm.reset();
+        self.vm.eval_deep_closure(closure)
+    }
+
     /// Prepare for evaluation, then fetch the metadata of `self.field`, or list the fields of the
     /// whole program if `self.field` is empty.
     pub fn query(&mut self) -> Result<Field, Error> {