2 files changed, 630 insertions, 0 deletions

diff --git a/crates/ide/src/lib.rs b/crates/ide/src/lib.rs
index 662da5a96..3f73c0632 100644
--- a/crates/ide/src/lib.rs
+++ b/crates/ide/src/lib.rs
@@ -37,6 +37,7 @@ mod hover;
 mod inlay_hints;
 mod join_lines;
 mod matching_brace;
+mod move_item;
 mod parent_module;
 mod references;
 mod fn_references;
@@ -76,6 +77,7 @@ pub use crate::{
     hover::{HoverAction, HoverConfig, HoverGotoTypeData, HoverResult},
     inlay_hints::{InlayHint, InlayHintsConfig, InlayKind},
     markup::Markup,
+    move_item::Direction,
     prime_caches::PrimeCachesProgress,
     references::{rename::RenameError, ReferenceSearchResult},
     runnables::{Runnable, RunnableKind, TestId},
@@ -583,6 +585,14 @@ impl Analysis {
         self.with_db(|db| annotations::resolve_annotation(db, annotation))
     }
 
+    pub fn move_item(
+        &self,
+        range: FileRange,
+        direction: Direction,
+    ) -> Cancelable<Option<TextEdit>> {
+        self.with_db(|db| move_item::move_item(db, range, direction))
+    }
+
     /// Performs an operation on that may be Canceled.
     fn with_db<F, T>(&self, f: F) -> Cancelable<T>
     where
diff --git a/crates/ide/src/move_item.rs b/crates/ide/src/move_item.rs
new file mode 100644
index 000000000..48690b073
--- /dev/null
+++ b/crates/ide/src/move_item.rs
@@ -0,0 +1,620 @@
+use std::iter::once;
+
+use hir::Semantics;
+use ide_db::{base_db::FileRange, RootDatabase};
+use itertools::Itertools;
+use syntax::{
+    algo, ast, match_ast, AstNode, NodeOrToken, SyntaxElement, SyntaxKind, SyntaxNode, TextRange,
+};
+use text_edit::{TextEdit, TextEditBuilder};
+
+pub enum Direction {
+    Up,
+    Down,
+}
+
+// Feature: Move Item
+//
+// Move item under cursor or selection up and down.
+//
+// |===
+// | Editor  | Action Name
+//
+// | VS Code | **Rust Analyzer: Move item up**
+// | VS Code | **Rust Analyzer: Move item down**
+// |===
+pub(crate) fn move_item(
+    db: &RootDatabase,
+    range: FileRange,
+    direction: Direction,
+) -> Option<TextEdit> {
+    let sema = Semantics::new(db);
+    let file = sema.parse(range.file_id);
+
+    let item = file.syntax().covering_element(range.range);
+    find_ancestors(item, direction, range.range)
+}
+
+fn find_ancestors(item: SyntaxElement, direction: Direction, range: TextRange) -> Option<TextEdit> {
+    let root = match item {
+        NodeOrToken::Node(node) => node,
+        NodeOrToken::Token(token) => token.parent()?,
+    };
+
+    let movable = [
+        SyntaxKind::ARG_LIST,
+        SyntaxKind::GENERIC_PARAM_LIST,
+        SyntaxKind::GENERIC_ARG_LIST,
+        SyntaxKind::VARIANT_LIST,
+        SyntaxKind::TYPE_BOUND_LIST,
+        SyntaxKind::MATCH_ARM,
+        SyntaxKind::PARAM,
+        SyntaxKind::LET_STMT,
+        SyntaxKind::EXPR_STMT,
+        SyntaxKind::MATCH_EXPR,
+        SyntaxKind::MACRO_CALL,
+        SyntaxKind::TYPE_ALIAS,
+        SyntaxKind::TRAIT,
+        SyntaxKind::IMPL,
+        SyntaxKind::MACRO_DEF,
+        SyntaxKind::STRUCT,
+        SyntaxKind::UNION,
+        SyntaxKind::ENUM,
+        SyntaxKind::FN,
+        SyntaxKind::MODULE,
+        SyntaxKind::USE,
+        SyntaxKind::STATIC,
+        SyntaxKind::CONST,
+        SyntaxKind::MACRO_RULES,
+    ];
+
+    let ancestor = once(root.clone())
+        .chain(root.ancestors())
+        .find(|ancestor| movable.contains(&ancestor.kind()))?;
+
+    move_in_direction(&ancestor, direction, range)
+}
+
+fn move_in_direction(
+    node: &SyntaxNode,
+    direction: Direction,
+    range: TextRange,
+) -> Option<TextEdit> {
+    match_ast! {
+        match node {
+            ast::ArgList(it) => swap_sibling_in_list(it.args(), range, direction),
+            ast::GenericParamList(it) => swap_sibling_in_list(it.generic_params(), range, direction),
+            ast::GenericArgList(it) => swap_sibling_in_list(it.generic_args(), range, direction),
+            ast::VariantList(it) => swap_sibling_in_list(it.variants(), range, direction),
+            ast::TypeBoundList(it) => swap_sibling_in_list(it.bounds(), range, direction),
+            _ => Some(replace_nodes(node, &match direction {
+                Direction::Up => node.prev_sibling(),
+                Direction::Down => node.next_sibling(),
+            }?))
+        }
+    }
+}
+
+fn swap_sibling_in_list<A: AstNode + Clone, I: Iterator<Item = A>>(
+    list: I,
+    range: TextRange,
+    direction: Direction,
+) -> Option<TextEdit> {
+    let (l, r) = list
+        .tuple_windows()
+        .filter(|(l, r)| match direction {
+            Direction::Up => r.syntax().text_range().contains_range(range),
+            Direction::Down => l.syntax().text_range().contains_range(range),
+        })
+        .next()?;
+
+    Some(replace_nodes(l.syntax(), r.syntax()))
+}
+
+fn replace_nodes(first: &SyntaxNode, second: &SyntaxNode) -> TextEdit {
+    let mut edit = TextEditBuilder::default();
+
+    algo::diff(first, second).into_text_edit(&mut edit);
+    algo::diff(second, first).into_text_edit(&mut edit);
+
+    edit.finish()
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::fixture;
+    use expect_test::{expect, Expect};
+
+    use crate::Direction;
+
+    fn check(ra_fixture: &str, expect: Expect, direction: Direction) {
+        let (analysis, range) = fixture::range(ra_fixture);
+        let edit = analysis.move_item(range, direction).unwrap().unwrap_or_default();
+        let mut file = analysis.file_text(range.file_id).unwrap().to_string();
+        edit.apply(&mut file);
+        expect.assert_eq(&file);
+    }
+
+    #[test]
+    fn test_moves_match_arm_up() {
+        check(
+            r#"
+fn main() {
+    match true {
+        true => {
+            println!("Hello, world");
+        },
+        false =>$0$0 {
+            println!("Test");
+        }
+    };
+}
+            "#,
+            expect![[r#"
+fn main() {
+    match true {
+        false => {
+            println!("Test");
+        },
+        true => {
+            println!("Hello, world");
+        }
+    };
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_moves_match_arm_down() {
+        check(
+            r#"
+fn main() {
+    match true {
+        true =>$0$0 {
+            println!("Hello, world");
+        },
+        false => {
+            println!("Test");
+        }
+    };
+}
+            "#,
+            expect![[r#"
+fn main() {
+    match true {
+        false => {
+            println!("Test");
+        },
+        true => {
+            println!("Hello, world");
+        }
+    };
+}
+            "#]],
+            Direction::Down,
+        );
+    }
+
+    #[test]
+    fn test_nowhere_to_move() {
+        check(
+            r#"
+fn main() {
+    match true {
+        true =>$0$0 {
+            println!("Hello, world");
+        },
+        false => {
+            println!("Test");
+        }
+    };
+}
+            "#,
+            expect![[r#"
+fn main() {
+    match true {
+        true => {
+            println!("Hello, world");
+        },
+        false => {
+            println!("Test");
+        }
+    };
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_moves_let_stmt_up() {
+        check(
+            r#"
+fn main() {
+    let test = 123;
+    let test2$0$0 = 456;
+}
+            "#,
+            expect![[r#"
+fn main() {
+    let test2 = 456;
+    let test = 123;
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_moves_expr_up() {
+        check(
+            r#"
+fn main() {
+    println!("Hello, world");
+    println!("All I want to say is...");$0$0
+}
+            "#,
+            expect![[r#"
+fn main() {
+    println!("All I want to say is...");
+    println!("Hello, world");
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_nowhere_to_move_stmt() {
+        check(
+            r#"
+fn main() {
+    println!("All I want to say is...");$0$0
+    println!("Hello, world");
+}
+            "#,
+            expect![[r#"
+fn main() {
+    println!("All I want to say is...");
+    println!("Hello, world");
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_move_item() {
+        check(
+            r#"
+fn main() {}
+
+fn foo() {}$0$0
+            "#,
+            expect![[r#"
+fn foo() {}
+
+fn main() {}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_move_impl_up() {
+        check(
+            r#"
+struct Yay;
+
+trait Wow {}
+
+impl Wow for Yay $0$0{}
+            "#,
+            expect![[r#"
+struct Yay;
+
+impl Wow for Yay {}
+
+trait Wow {}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_move_use_up() {
+        check(
+            r#"
+use std::vec::Vec;
+use std::collections::HashMap$0$0;
+            "#,
+            expect![[r#"
+use std::collections::HashMap;
+use std::vec::Vec;
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_moves_match_expr_up() {
+        check(
+            r#"
+fn main() {
+    let test = 123;
+
+    $0match test {
+        456 => {},
+        _ => {}
+    };$0
+}
+            "#,
+            expect![[r#"
+fn main() {
+    match test {
+        456 => {},
+        _ => {}
+    };
+
+    let test = 123;
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_moves_param_up() {
+        check(
+            r#"
+fn test(one: i32, two$0$0: u32) {}
+
+fn main() {
+    test(123, 456);
+}
+            "#,
+            expect![[r#"
+fn test(two: u32, one: i32) {}
+
+fn main() {
+    test(123, 456);
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_moves_arg_up() {
+        check(
+            r#"
+fn test(one: i32, two: u32) {}
+
+fn main() {
+    test(123, 456$0$0);
+}
+            "#,
+            expect![[r#"
+fn test(one: i32, two: u32) {}
+
+fn main() {
+    test(456, 123);
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_moves_arg_down() {
+        check(
+            r#"
+fn test(one: i32, two: u32) {}
+
+fn main() {
+    test(123$0$0, 456);
+}
+            "#,
+            expect![[r#"
+fn test(one: i32, two: u32) {}
+
+fn main() {
+    test(456, 123);
+}
+            "#]],
+            Direction::Down,
+        );
+    }
+
+    #[test]
+    fn test_nowhere_to_move_arg() {
+        check(
+            r#"
+fn test(one: i32, two: u32) {}
+
+fn main() {
+    test(123$0$0, 456);
+}
+            "#,
+            expect![[r#"
+fn test(one: i32, two: u32) {}
+
+fn main() {
+    test(123, 456);
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_moves_generic_param_up() {
+        check(
+            r#"
+struct Test<A, B$0$0>(A, B);
+
+fn main() {}
+            "#,
+            expect![[r#"
+struct Test<B, A>(A, B);
+
+fn main() {}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_moves_generic_arg_up() {
+        check(
+            r#"
+struct Test<A, B>(A, B);
+
+fn main() {
+    let t = Test::<i32, &str$0$0>(123, "yay");
+}
+            "#,
+            expect![[r#"
+struct Test<A, B>(A, B);
+
+fn main() {
+    let t = Test::<&str, i32>(123, "yay");
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_moves_variant_up() {
+        check(
+            r#"
+enum Hello {
+    One,
+    Two$0$0
+}
+
+fn main() {}
+            "#,
+            expect![[r#"
+enum Hello {
+    Two,
+    One
+}
+
+fn main() {}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_moves_type_bound_up() {
+        check(
+            r#"
+trait One {}
+
+trait Two {}
+
+fn test<T: One + Two$0$0>(t: T) {}
+
+fn main() {}
+            "#,
+            expect![[r#"
+trait One {}
+
+trait Two {}
+
+fn test<T: Two + One>(t: T) {}
+
+fn main() {}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_prioritizes_trait_items() {
+        check(
+            r#"
+struct Test;
+
+trait Yay {
+    type One;
+
+    type Two;
+
+    fn inner();
+}
+
+impl Yay for Test {
+    type One = i32;
+
+    type Two = u32;
+
+    fn inner() {$0$0
+        println!("Mmmm");
+    }
+}
+            "#,
+            expect![[r#"
+struct Test;
+
+trait Yay {
+    type One;
+
+    type Two;
+
+    fn inner();
+}
+
+impl Yay for Test {
+    type One = i32;
+
+    fn inner() {
+        println!("Mmmm");
+    }
+
+    type Two = u32;
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_weird_nesting() {
+        check(
+            r#"
+fn test() {
+    mod hello {
+        fn inner() {}
+    }
+
+    mod hi {$0$0
+        fn inner() {}
+    }
+}
+            "#,
+            expect![[r#"
+fn test() {
+    mod hi {
+        fn inner() {}
+    }
+
+    mod hello {
+        fn inner() {}
+    }
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn handles_empty_file() {
+        check(r#"$0$0"#, expect![[r#""#]], Direction::Up);
+    }
+}