Simplify expressions (#3389)

* WIP: experiment with simpler expressions

* fix simple invoke

* update tests

* fix a few tests

* Make paren parsing more robust

* fix external args

* Remove old invocation

* Update tests

* Update tests

crates/nu-engine/src/evaluate/expr.rs

@@ -5,6 +5,7 @@ use log::{log_enabled, trace};
 use crate::evaluation_context::EvaluationContext;
 use nu_errors::ShellError;
 use nu_protocol::hir::SpannedExpression;
+use nu_protocol::{UntaggedValue, Value};
 use nu_stream::{InputStream, ToInputStream};
 
 pub(crate) fn run_expression_block(
@@ -18,5 +19,11 @@ pub(crate) fn run_expression_block(
 
     let output = evaluate_baseline_expr(expr, ctx)?;
 
-    Ok(std::iter::once(Ok(output)).to_input_stream())
+    match output {
+        Value {
+            value: UntaggedValue::Table(x),
+            ..
+        } => Ok(InputStream::from_stream(x.into_iter())),
+        output => Ok(std::iter::once(Ok(output)).to_input_stream()),
+    }
 }

crates/nu-engine/tests/evaluate/invocation.rs

@@ -6,7 +6,7 @@ fn test_parse_invocation_with_range() {
         cwd: ".",
         r#"
         let foo = 3
-        echo $(echo 1..$foo | each { echo $it }) | to json
+        echo (echo 1..$foo | each { $it }) | to json
         "#
     );
     assert_eq!(actual.out, "[1,2,3]")