Add ide-assist: unmerge_to_guarded_arm

crates/ide-assists/src/handlers/unmerge_match_arm.rs

@@ -104,6 +104,70 @@ pub(crate) fn unmerge_match_arm(acc: &mut Assists, ctx: &AssistContext<'_>) -> O
     )
 }
 
+// Assist: unmerge_to_guarded_arm
+//
+// Unmerge into guarded match arm.
+//
+// ```
+// enum Kind { Num(u32) }
+//
+// fn handle(kind: Kind) {
+//     match kind {
+//         Kind::Num(n) $0=> foo(n),
+//     }
+// }
+// ```
+// ->
+// ```
+// enum Kind { Num(u32) }
+//
+// fn handle(kind: Kind) {
+//     match kind {
+//         Kind::Num(n) if $0 => foo(n),
+//         Kind::Num(n) => foo(n),
+//     }
+// }
+// ```
+pub(crate) fn unmerge_to_guarded_arm(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<()> {
+    let arrow_token = ctx.find_token_syntax_at_offset(T![=>])?;
+    let match_arm = ast::MatchArm::cast(arrow_token.parent()?)?;
+
+    if match_arm.guard().is_some() {
+        return None;
+    }
+
+    acc.add(
+        AssistId::refactor_rewrite("unmerge_to_guarded_arm"),
+        "Unmerge to guarded match arm",
+        match_arm.syntax().text_range(),
+        |edit| {
+            let make = SyntaxFactory::without_mappings();
+            let mut editor = edit.make_editor(match_arm.syntax());
+
+            let guard = vec![
+                make.token(T![if]).into(),
+                make.whitespace(" ").into(),
+                make.whitespace(" ").into(),
+            ];
+            if let Some(cap) = ctx.config.snippet_cap {
+                editor.add_annotation(&guard[2], edit.make_tabstop_before(cap));
+            }
+            editor.insert_all(Position::before(arrow_token), guard);
+
+            let new_arm = match_arm.syntax().clone_for_update();
+            editor.insert(Position::after(match_arm.syntax()), &new_arm);
+
+            if let Some(prev) = new_arm.prev_sibling_or_token()
+                && prev.kind() == SyntaxKind::WHITESPACE
+            {
+                editor.insert(Position::after(match_arm.syntax()), prev);
+            }
+
+            edit.add_file_edits(ctx.vfs_file_id(), editor);
+        },
+    )
+}
+
 #[cfg(test)]
 mod tests {
     use crate::tests::{check_assist, check_assist_not_applicable};
@@ -278,6 +342,46 @@ fn main() {
         X::B => {}
     }
 }
+"#,
+        );
+    }
+
+    #[test]
+    fn unmerge_to_guarded_arm_with_block() {
+        check_assist(
+            unmerge_to_guarded_arm,
+            r#"
+fn main() {
+    match () {
+        () $0=> {
+            foo()
+        }
+    };
+}"#,
+            r#"
+fn main() {
+    match () {
+        () if $0 => {
+            foo()
+        }
+        () => {
+            foo()
+        }
+    };
+}"#,
+        );
+    }
+
+    #[test]
+    fn unmerge_to_guarded_arm_guarded() {
+        check_assist_not_applicable(
+            unmerge_to_guarded_arm,
+            r#"
+fn main() {
+    match () {
+        () if true $0=> {}
+    };
+}
 "#,
         );
     }

crates/ide-assists/src/lib.rs

@@ -376,6 +376,7 @@ mod handlers {
             toggle_ignore::toggle_ignore,
             toggle_macro_delimiter::toggle_macro_delimiter,
             unmerge_match_arm::unmerge_match_arm,
+            unmerge_match_arm::unmerge_to_guarded_arm,
             unmerge_imports::unmerge_imports,
             unnecessary_async::unnecessary_async,
             unqualify_method_call::unqualify_method_call,

crates/ide-assists/src/tests/generated.rs

@@ -3653,6 +3653,32 @@ fn handle(action: Action) {
     )
 }
 
+#[test]
+fn doctest_unmerge_to_guarded_arm() {
+    check_doc_test(
+        "unmerge_to_guarded_arm",
+        r#####"
+enum Kind { Num(u32) }
+
+fn handle(kind: Kind) {
+    match kind {
+        Kind::Num(n) $0=> foo(n),
+    }
+}
+"#####,
+        r#####"
+enum Kind { Num(u32) }
+
+fn handle(kind: Kind) {
+    match kind {
+        Kind::Num(n) if $0 => foo(n),
+        Kind::Num(n) => foo(n),
+    }
+}
+"#####,
+    )
+}
+
 #[test]
 fn doctest_unnecessary_async() {
     check_doc_test(

crates/syntax/src/ast/make.rs

@@ -1355,7 +1355,7 @@ pub mod tokens {
 
     pub(super) static SOURCE_FILE: LazyLock<Parse<SourceFile>> = LazyLock::new(|| {
         SourceFile::parse(
-            "use crate::foo; const C: <()>::Item = ( true && true , true || true , 1 != 1, 2 == 2, 3 < 3, 4 <= 4, 5 > 5, 6 >= 6, !true, *p, &p , &mut p, async { let _ @ [] }, while loop {} {})\n;\n\nunsafe impl A for B where: {}",
+            "use crate::foo; const C: <()>::Item = ( true && true , true || true , 1 != 1, 2 == 2, 3 < 3, 4 <= 4, 5 > 5, 6 >= 6, !true, *p, &p , &mut p, async { let _ @ [] }, while loop {} {}, if false { false } else { true })\n;\n\nunsafe impl A for B where: {}",
             Edition::CURRENT,
         )
     });