Add autofix suggestion for method calls mistaken as field access

CHANGELOG.md

@@ -11,6 +11,9 @@ Added a warning for unnecessary `let` bindings where a variable is
 bound and immediately returned (e.g. `let x = foo() x` can be
 simplified to `foo()`), with an autofix.
 
+Added an autofix for `some_list.len` suggesting `some_list.len()`
+when accessing a name that matches a method on the type.
+
 ## Commands
 
 Added :load to evaluate all definitions in a file and switch to that

src/checks/type_checker.rs

@@ -1167,13 +1167,35 @@ impl TypeCheckVisitor<'_> {
 
                     Type::error("No struct field with this name")
                 } else {
+                    let methods = self
+                        .env
+                        .types
+                        .get(&recv_ty_name)
+                        .cloned()
+                        .map(|tdm| tdm.methods)
+                        .unwrap_or_default();
+
+                    let mut fixes = vec![];
+                    let suggest =
+                        if methods.contains_key(&field_sym.name) {
+                            fixes.push(Autofix {
+                                description: format!("Use `{}()` here.", field_sym.name),
+                                position: field_sym.position.clone(),
+                                new_text: format!("{}()", field_sym.name),
+                            });
+
+                            format!(" Did you mean `{}()`?", field_sym.name)
+                        } else {
+                            "".to_owned()
+                        };
+
                     self.diagnostics.push(Diagnostic {
                         notes: vec![],
-                        fixes: vec![],
+                        fixes,
                         severity: Severity::Error,
                         message: ErrorMessage(vec![
                             msgcode!("{}", recv_ty_name),
-                            msgtext!(" is not a struct."),
+                            msgtext!(" is not a struct.{}", suggest),
                         ]),
                         position: field_sym.position.clone(),
                     });
@@ -1182,13 +1204,35 @@ impl TypeCheckVisitor<'_> {
                 }
             }
             _ => {
+                let methods = self
+                    .env
+                    .types
+                    .get(&recv_ty_name)
+                    .cloned()
+                    .map(|tdm| tdm.methods)
+                    .unwrap_or_default();
+
+                let mut fixes = vec![];
+                let suggest =
+                    if methods.contains_key(&field_sym.name) {
+                        fixes.push(Autofix {
+                            description: format!("Use `{}()` here.", field_sym.name),
+                            position: field_sym.position.clone(),
+                            new_text: format!("{}()", field_sym.name),
+                        });
+
+                        format!(" Did you mean `{}()`?", field_sym.name)
+                    } else {
+                        "".to_owned()
+                    };
+
                 self.diagnostics.push(Diagnostic {
                     notes: vec![],
-                    fixes: vec![],
+                    fixes,
                     severity: Severity::Error,
                     message: ErrorMessage(vec![
                         msgcode!("{}", recv_ty_name),
-                        msgtext!(" is not a struct."),
+                        msgtext!(" is not a struct.{}", suggest),
                     ]),
                     position: field_sym.position.clone(),
                 });

src/test_files/check_fix/list_len_method.gdn

@@ -0,0 +1,11 @@
+{
+  let items = [1, 2, 3]
+  items.len
+}
+
+// args: check --fix --stdout
+// expected stdout:
+// {
+//   let items = [1, 2, 3]
+//   items.len()
+// }