Add row conditions

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

@@ -15,6 +15,7 @@ pub enum Expr {
     Call(Box<Call>),
     ExternalCall(Vec<u8>, Vec<Vec<u8>>),
     Operator(Operator),
+    RowCondition(VarId, Box<Expression>),
     BinaryOp(Box<Expression>, Box<Expression>, Box<Expression>), //lhs, op, rhs
     Subexpression(BlockId),
     Block(BlockId),

crates/nu-protocol/src/value/mod.rs

@@ -277,6 +277,10 @@ impl Value {
 
         Ok(current)
     }
+
+    pub fn is_true(&self) -> bool {
+        matches!(self, Value::Bool { val: true, .. })
+    }
 }
 
 impl PartialEq for Value {