Enable string interpolation for environment shorthand (#5463)

crates/nu-parser/src/parser.rs

@@ -4287,13 +4287,16 @@ pub fn parse_expression(
                 },
             );
             let rhs = if spans[pos].start + point < spans[pos].end {
-                parse_string_strict(
+                let rhs_span = Span {
-                    working_set,
+                    start: spans[pos].start + point,
-                    Span {
+                    end: spans[pos].end,
-                        start: spans[pos].start + point,
+                };
-                        end: spans[pos].end,
+
-                    },
+                if working_set.get_span_contents(rhs_span).starts_with(b"$") {
-                )
+                    parse_dollar_expr(working_set, rhs_span, expand_aliases_denylist)
+                } else {
+                    parse_string_strict(working_set, rhs_span)
+                }
             } else {
                 (
                     Expression {

tests/shell/environment/env.rs

@@ -22,6 +22,15 @@ fn env_shorthand_with_equals() {
     assert_eq!(actual.out, "my_module=info");
 }
 
+#[test]
+fn env_shorthand_with_interpolation() {
+    let actual = nu!(cwd: ".", r#"
+        let num = 123
+        FOO=$"($num) bar" echo $env.FOO
+        "#);
+    assert_eq!(actual.out, "123 bar");
+}
+
 #[test]
 fn env_shorthand_with_comma_equals() {
     let actual = nu!(cwd: ".", r#"