Add UnexpectedFunction error for functions called outside other funct…

…ions

compiler-core/src/parse.rs

@@ -2171,10 +2171,7 @@ where
                             let _ = self.next_tok(); // name
 
                             parse_error(
-                                ParseErrorType::UnexpectedToken {
-                                    expected: vec!["A constant definition".to_string()],
-                                    hint: Some("Functions cannot be called in constant declarations. You can use let instead (and make sure it is inside a scope)".to_string())
-                                },
+                                ParseErrorType::UnexpectedFunction,
                                 SrcSpan { start, end: end + 1},
                             )
                         } else {

compiler-core/src/parse/error.rs

@@ -201,6 +201,10 @@ utf16_codepoint, utf32_codepoint, signed, unsigned, big, little, native, size, u
                     "from the stdlib's `gleam/string` module".into(),
                 ],
             ),
+            ParseErrorType::UnexpectedFunction => (
+                "Functions can only be called within other functions.",
+                vec![]
+            )
         }
     }
 }
@@ -246,6 +250,7 @@ pub enum ParseErrorType {
         hint: Option<String>,
     },
     ExpectedBoolean,
+    UnexpectedFunction, // a function was used called outside of another function
     // A variable was assigned or discarded on the left hand side of a <> pattern
     ConcatPatternVariableLeftHandSide,
 }

compiler-core/src/parse/tests.rs

@@ -361,3 +361,8 @@ fn assign_left_hand_side_of_concat_pattern() {
         "#
     );
 }
+
+#[test]
+fn function_called_outside_function() {
+    assert_error!("const first = list.at([1], 0)");
+}