1 files changed, 293 insertions, 0 deletions

diff --git a/crates/assists/src/handlers/move_guard.rs b/crates/assists/src/handlers/move_guard.rs
new file mode 100644
index 000000000..452115fe6
--- /dev/null
+++ b/crates/assists/src/handlers/move_guard.rs
@@ -0,0 +1,293 @@
+use syntax::{
+    ast::{edit::AstNodeEdit, make, AstNode, IfExpr, MatchArm},
+    SyntaxKind::WHITESPACE,
+};
+
+use crate::{AssistContext, AssistId, AssistKind, Assists};
+
+// Assist: move_guard_to_arm_body
+//
+// Moves match guard into match arm body.
+//
+// ```
+// enum Action { Move { distance: u32 }, Stop }
+//
+// fn handle(action: Action) {
+//     match action {
+//         Action::Move { distance } <|>if distance > 10 => foo(),
+//         _ => (),
+//     }
+// }
+// ```
+// ->
+// ```
+// enum Action { Move { distance: u32 }, Stop }
+//
+// fn handle(action: Action) {
+//     match action {
+//         Action::Move { distance } => if distance > 10 {
+//             foo()
+//         },
+//         _ => (),
+//     }
+// }
+// ```
+pub(crate) fn move_guard_to_arm_body(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let match_arm = ctx.find_node_at_offset::<MatchArm>()?;
+    let guard = match_arm.guard()?;
+    let space_before_guard = guard.syntax().prev_sibling_or_token();
+
+    let guard_condition = guard.expr()?;
+    let arm_expr = match_arm.expr()?;
+    let if_expr = make::expr_if(
+        make::condition(guard_condition, None),
+        make::block_expr(None, Some(arm_expr.clone())),
+    )
+    .indent(arm_expr.indent_level());
+
+    let target = guard.syntax().text_range();
+    acc.add(
+        AssistId("move_guard_to_arm_body", AssistKind::RefactorRewrite),
+        "Move guard to arm body",
+        target,
+        |edit| {
+            match space_before_guard {
+                Some(element) if element.kind() == WHITESPACE => {
+                    edit.delete(element.text_range());
+                }
+                _ => (),
+            };
+
+            edit.delete(guard.syntax().text_range());
+            edit.replace_ast(arm_expr, if_expr);
+        },
+    )
+}
+
+// Assist: move_arm_cond_to_match_guard
+//
+// Moves if expression from match arm body into a guard.
+//
+// ```
+// enum Action { Move { distance: u32 }, Stop }
+//
+// fn handle(action: Action) {
+//     match action {
+//         Action::Move { distance } => <|>if distance > 10 { foo() },
+//         _ => (),
+//     }
+// }
+// ```
+// ->
+// ```
+// enum Action { Move { distance: u32 }, Stop }
+//
+// fn handle(action: Action) {
+//     match action {
+//         Action::Move { distance } if distance > 10 => foo(),
+//         _ => (),
+//     }
+// }
+// ```
+pub(crate) fn move_arm_cond_to_match_guard(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let match_arm: MatchArm = ctx.find_node_at_offset::<MatchArm>()?;
+    let match_pat = match_arm.pat()?;
+
+    let arm_body = match_arm.expr()?;
+    let if_expr: IfExpr = IfExpr::cast(arm_body.syntax().clone())?;
+    let cond = if_expr.condition()?;
+    let then_block = if_expr.then_branch()?;
+
+    // Not support if with else branch
+    if if_expr.else_branch().is_some() {
+        return None;
+    }
+    // Not support moving if let to arm guard
+    if cond.pat().is_some() {
+        return None;
+    }
+
+    let buf = format!(" if {}", cond.syntax().text());
+
+    let target = if_expr.syntax().text_range();
+    acc.add(
+        AssistId("move_arm_cond_to_match_guard", AssistKind::RefactorRewrite),
+        "Move condition to match guard",
+        target,
+        |edit| {
+            let then_only_expr = then_block.statements().next().is_none();
+
+            match &then_block.expr() {
+                Some(then_expr) if then_only_expr => {
+                    edit.replace(if_expr.syntax().text_range(), then_expr.syntax().text())
+                }
+                _ => edit.replace(if_expr.syntax().text_range(), then_block.syntax().text()),
+            }
+
+            edit.insert(match_pat.syntax().text_range().end(), buf);
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::tests::{check_assist, check_assist_not_applicable, check_assist_target};
+
+    #[test]
+    fn move_guard_to_arm_body_target() {
+        check_assist_target(
+            move_guard_to_arm_body,
+            r#"
+fn main() {
+    match 92 {
+        x <|>if x > 10 => false,
+        _ => true
+    }
+}
+"#,
+            r#"if x > 10"#,
+        );
+    }
+
+    #[test]
+    fn move_guard_to_arm_body_works() {
+        check_assist(
+            move_guard_to_arm_body,
+            r#"
+fn main() {
+    match 92 {
+        x <|>if x > 10 => false,
+        _ => true
+    }
+}
+"#,
+            r#"
+fn main() {
+    match 92 {
+        x => if x > 10 {
+            false
+        },
+        _ => true
+    }
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn move_guard_to_arm_body_works_complex_match() {
+        check_assist(
+            move_guard_to_arm_body,
+            r#"
+fn main() {
+    match 92 {
+        <|>x @ 4 | x @ 5    if x > 5 => true,
+        _ => false
+    }
+}
+"#,
+            r#"
+fn main() {
+    match 92 {
+        x @ 4 | x @ 5 => if x > 5 {
+            true
+        },
+        _ => false
+    }
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn move_arm_cond_to_match_guard_works() {
+        check_assist(
+            move_arm_cond_to_match_guard,
+            r#"
+fn main() {
+    match 92 {
+        x => if x > 10 { <|>false },
+        _ => true
+    }
+}
+"#,
+            r#"
+fn main() {
+    match 92 {
+        x if x > 10 => false,
+        _ => true
+    }
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn move_arm_cond_to_match_guard_if_let_not_works() {
+        check_assist_not_applicable(
+            move_arm_cond_to_match_guard,
+            r#"
+fn main() {
+    match 92 {
+        x => if let 62 = x { <|>false },
+        _ => true
+    }
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn move_arm_cond_to_match_guard_if_empty_body_works() {
+        check_assist(
+            move_arm_cond_to_match_guard,
+            r#"
+fn main() {
+    match 92 {
+        x => if x > 10 { <|> },
+        _ => true
+    }
+}
+"#,
+            r#"
+fn main() {
+    match 92 {
+        x if x > 10 => {  },
+        _ => true
+    }
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn move_arm_cond_to_match_guard_if_multiline_body_works() {
+        check_assist(
+            move_arm_cond_to_match_guard,
+            r#"
+fn main() {
+    match 92 {
+        x => if x > 10 {
+            92;<|>
+            false
+        },
+        _ => true
+    }
+}
+"#,
+            r#"
+fn main() {
+    match 92 {
+        x if x > 10 => {
+            92;
+            false
+        },
+        _ => true
+    }
+}
+"#,
+        );
+    }
+}