Fix up calls and pipelines

crates/nu-protocol/src/ast/pipeline.rs

@@ -17,4 +17,8 @@ impl Pipeline {
             expressions: vec![],
         }
     }
+
+    pub fn from_vec(expressions: Vec<Expression>) -> Pipeline {
+        Self { expressions }
+    }
 }

crates/nu-protocol/src/ast/statement.rs

@@ -1,9 +1,8 @@
-use super::{Expression, Pipeline};
+use super::Pipeline;
 use crate::DeclId;
 
 #[derive(Debug, Clone)]
 pub enum Statement {
     Declaration(DeclId),
     Pipeline(Pipeline),
-    Expression(Expression),
 }

crates/nu-protocol/src/value.rs

@@ -197,6 +197,12 @@ impl Value {
             Value::Nothing { .. } => String::new(),
         }
     }
+
+    pub fn nothing() -> Value {
+        Value::Nothing {
+            span: Span::unknown(),
+        }
+    }
 }
 
 impl PartialEq for Value {