Paren interpolation (#3452)

* Switch interp to use parens

* improve interp parsing

tests/shell/pipeline/commands/internal.rs

@@ -118,7 +118,7 @@ fn string_interpolation_with_it() {
     let actual = nu!(
         cwd: ".",
         r#"
-                    echo "foo" | each { echo $"{$it}" }
+                    echo "foo" | each { echo $"($it)" }
             "#
     );
 
@@ -130,7 +130,7 @@ fn string_interpolation_with_it_column_path() {
     let actual = nu!(
         cwd: ".",
         r#"
-                    echo [[name]; [sammie]] | each { echo $"{$it.name}" }
+                    echo [[name]; [sammie]] | each { echo $"($it.name)" }
         "#
     );
 
@@ -142,13 +142,25 @@ fn string_interpolation_shorthand_overlap() {
     let actual = nu!(
         cwd: ".",
         r#"
-                    $"3 + 4 = {3 + 4}"
+                    $"3 + 4 = (3 + 4)"
         "#
     );
 
     assert_eq!(actual.out, "3 + 4 = 7");
 }
 
+#[test]
+fn string_interpolation_and_paren() {
+    let actual = nu!(
+        cwd: ".",
+        r#"
+                    $"a paren is ('(')"
+        "#
+    );
+
+    assert_eq!(actual.out, "a paren is (");
+}
+
 #[test]
 fn bignum_large_integer() {
     let actual = nu!(