Aliasing math expression shows error earlier (#8779)

crates/nu-command/tests/commands/alias.rs

@@ -114,7 +114,19 @@ fn alias_wont_recurse2() {
     })
 }
 
-// Isuue https://github.com/nushell/nushell/issues/8103
+#[test]
+fn alias_invalid_expression() {
+    let actual = nu!(r#" alias spam = 'foo' "#);
+    assert!(actual.err.contains("cant_alias_expression"));
+
+    let actual = nu!(r#" alias spam = ([1 2 3] | length) "#);
+    assert!(actual.err.contains("cant_alias_expression"));
+
+    let actual = nu!(r#" alias spam = 0..12 "#);
+    assert!(actual.err.contains("cant_alias_expression"));
+}
+
+// Issue https://github.com/nushell/nushell/issues/8103
 #[test]
 fn alias_multiword_name() {
     let actual = nu!(r#"alias `foo bar` = echo 'test'; foo bar"#);

crates/nu-command/tests/commands/help.rs

@@ -259,8 +259,8 @@ fn help_module_sorted_aliases() {
             "spam.nu",
             r#"
                 module SPAM {
-                    export alias z = 'z'
+                    export alias z = echo 'z'
-                    export alias a = 'a'
+                    export alias a = echo 'a'
                 }
             "#,
         )]);

crates/nu-command/tests/commands/source_env.rs

@@ -275,7 +275,7 @@ fn source_env_is_scoped() {
             "spam.nu",
             r#"
                 def no-name-similar-to-this [] { 'no-name-similar-to-this' }
-                    alias nor-similar-to-this = 'nor-similar-to-this'
+                alias nor-similar-to-this = echo 'nor-similar-to-this'
             "#,
         )]);
 

crates/nu-parser/src/errors.rs

@@ -109,6 +109,13 @@ pub enum ParseError {
     )]
     CantAliasKeyword(String, #[label("not supported in alias")] Span),
 
+    #[error("Can't create alias to expression.")]
+    #[diagnostic(
+        code(nu::parser::cant_alias_expression),
+        help("Only command calls can be aliased.")
+    )]
+    CantAliasExpression(String, #[label("aliasing {0} is not supported")] Span),
+
     #[error("Unknown operator")]
     #[diagnostic(code(nu::parser::unknown_operator), help("{1}"))]
     UnknownOperator(
@@ -434,6 +441,7 @@ impl ParseError {
             ParseError::ExpectedKeyword(_, s) => *s,
             ParseError::UnexpectedKeyword(_, s) => *s,
             ParseError::CantAliasKeyword(_, s) => *s,
+            ParseError::CantAliasExpression(_, s) => *s,
             ParseError::BuiltinCommandInPipeline(_, s) => *s,
             ParseError::AssignInPipeline(_, _, _, s) => *s,
             ParseError::LetBuiltinVar(_, s) => *s,

crates/nu-parser/src/parse_keywords.rs

@@ -18,13 +18,14 @@ pub const PLUGIN_DIRS_VAR: &str = "NU_PLUGIN_DIRS";
 
 use crate::{
     eval::{eval_constant, value_as_string},
+    is_math_expression_like,
     known_external::KnownExternal,
     lex,
     lite_parser::{lite_parse, LiteCommand, LiteElement},
     parser::{
-        check_call, check_name, garbage, garbage_pipeline, parse, parse_call, parse_import_pattern,
+        check_call, check_name, garbage, garbage_pipeline, parse, parse_call, parse_expression,
-        parse_internal_call, parse_multispan_value, parse_signature, parse_string, parse_value,
+        parse_import_pattern, parse_internal_call, parse_multispan_value, parse_signature,
-        parse_var_with_opt_type, trim_quotes, ParsedInternalCall,
+        parse_string, parse_value, parse_var_with_opt_type, trim_quotes, ParsedInternalCall,
     },
     unescape_unquote_string, ParseError, Token, TokenContents,
 };
@@ -798,6 +799,27 @@ pub fn parse_alias(
 
             let replacement_spans = &spans[(split_id + 2)..];
 
+            if is_math_expression_like(working_set, replacement_spans[0], expand_aliases_denylist) {
+                // TODO: Maybe we need to implement a Display trait for Expression?
+                let (expr, _) = parse_expression(
+                    working_set,
+                    replacement_spans,
+                    expand_aliases_denylist,
+                    false,
+                );
+
+                let msg = format!("{:?}", expr.expr);
+                let msg_parts: Vec<&str> = msg.split('(').collect();
+
+                return (
+                    alias_pipeline,
+                    Some(ParseError::CantAliasExpression(
+                        msg_parts[0].to_string(),
+                        replacement_spans[0],
+                    )),
+                );
+            }
+
             let (expr, err) = parse_call(
                 working_set,
                 replacement_spans,