fix: fix formatter adding -- to multiple use statements

sway-fmt/src/fmt.rs

@@ -341,25 +341,25 @@ struct Rgb {
     blue: u64,
 }
 
-struct Structure {
+struct Bimbam {
     age: u32,
 
     name: string,
 }
 
-struct Structure {
+struct Building {
     age: u32, /* completely meaningless multiline comment
         not sure why would anyone write this but let's deal with it as well!
     */
     name: string,
 }
 
-struct Structure {
+struct Darts {
     age: u32,
     name: string, // super comment
 }
 
-struct Structure {
+struct Lighthouse {
     age: u32,
     name: string, // super comment
 }
@@ -447,32 +447,32 @@ struct Rgb {
     blue: u64,
 }
 
-struct Structure {
+struct Bimbam {
 
     age: u32,
 
     name: string,
 
 }
 
-struct Structure {
+struct Building {
     age: u32, /* completely meaningless multiline comment
         not sure why would anyone write this but let's deal with it as well!
     */
     name: string
 }
 
-struct Structure {
+struct Darts {
     age: u32,
     name: string// super comment
 }
 
-struct Structure {
+struct Lighthouse {
     age: u32,
     name: string, // super comment
 }
 
-struct Vehicle 
+struct Vehicle
           { age:       u32,          name: string , // some comment middle of nowhere
 }
 
@@ -641,4 +641,23 @@ fn one_liner() -> bool {
         let (_, formatted_code) = result.unwrap();
         assert_eq!(correct_sway_code, formatted_code);
     }
+
+    #[test]
+    // This test is here to check that the `use` statements are properly formatted
+    // Currently, there is a hard-to-diagnose bug which adds a leading `--` to the first
+    // `use` statement
+    fn test_use_statement() {
+        let expected_sway = r#"script;
+use std::chain::{panic,log_u8};
+use std::chain::assert;
+use std::address::{Address,Address};
+
+fn main() {
+}
+"#;
+        let result = get_formatted_data(expected_sway.into(), OPTIONS);
+        assert!(result.is_ok());
+        let (_, formatted_code) = result.unwrap();
+        assert_eq!(formatted_code, expected_sway);
+    }
 }

sway-fmt/src/traversal.rs

@@ -48,7 +48,7 @@ pub fn traverse_for_changes(parse_tree: &SwayParseTree) -> Vec<Change> {
     let mut changes = vec![];
 
     for node in &parse_tree.tree.root_nodes {
-        traverse_ast_node(node, &mut changes)
+        traverse_ast_node(node, &mut changes);
     }
 
     changes.sort_by(|a, b| a.start.cmp(&b.start));
@@ -69,7 +69,15 @@ fn traverse_ast_node(ast_node: &AstNode, changes: &mut Vec<Change>) {
         }
 
         AstNodeContent::UseStatement(_) => {
-            changes.push(Change::new(&ast_node.span, ChangeType::UseStatement));
+            // The AST generates one root node per use statement, we must avoid duplicating them
+            // while formatting
+            if changes.is_empty() {
+                changes.push(Change::new(&ast_node.span, ChangeType::UseStatement));
+            }
+            let previous_start = changes.last().unwrap().start;
+            if previous_start != ast_node.span.start() {
+                changes.push(Change::new(&ast_node.span, ChangeType::UseStatement));
+            }
         }
 
         AstNodeContent::IncludeStatement(_) => {