Improve range parsing and handling (#2506)

* Improve range parsing and handling

* linting

crates/nu-protocol/src/hir.rs

@@ -600,6 +600,21 @@ impl SpannedExpression {
             Expression::Binary(binary) => {
                 binary.left.has_shallow_it_usage() || binary.right.has_shallow_it_usage()
             }
+            Expression::Range(range) => {
+                let left = if let Some(left) = &range.left {
+                    left.has_shallow_it_usage()
+                } else {
+                    false
+                };
+
+                let right = if let Some(right) = &range.right {
+                    right.has_shallow_it_usage()
+                } else {
+                    false
+                };
+
+                left || right
+            }
             Expression::Variable(Variable::It(_)) => true,
             Expression::Path(path) => path.head.has_shallow_it_usage(),
             Expression::List(list) => {
@@ -890,20 +905,27 @@ impl ShellTypeName for Synthetic {
 
 #[derive(Debug, Ord, PartialOrd, Eq, PartialEq, Clone, Hash, Deserialize, Serialize)]
 pub struct Range {
-    pub left: SpannedExpression,
+    pub left: Option<SpannedExpression>,
     pub dotdot: Span,
-    pub right: SpannedExpression,
+    pub right: Option<SpannedExpression>,
 }
 
 impl PrettyDebugWithSource for Range {
     fn pretty_debug(&self, source: &str) -> DebugDocBuilder {
         b::delimit(
             "<",
-            self.left.pretty_debug(source)
-                + b::space()
+            (if let Some(left) = &self.left {
+                left.pretty_debug(source)
+            } else {
+                DebugDocBuilder::blank()
+            }) + b::space()
                 + b::keyword(self.dotdot.slice(source))
                 + b::space()
-                + self.right.pretty_debug(source),
+                + (if let Some(right) = &self.right {
+                    right.pretty_debug(source)
+                } else {
+                    DebugDocBuilder::blank()
+                }),
             ">",
         )
         .group()
@@ -1083,7 +1105,11 @@ impl Expression {
         Expression::Literal(Literal::Operator(operator))
     }
 
-    pub fn range(left: SpannedExpression, dotdot: Span, right: SpannedExpression) -> Expression {
+    pub fn range(
+        left: Option<SpannedExpression>,
+        dotdot: Span,
+        right: Option<SpannedExpression>,
+    ) -> Expression {
         Expression::Range(Box::new(Range {
             left,
             dotdot,