Add remove_parentheses assist

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

@@ -0,0 +1,86 @@
+use syntax::{ast, AstNode, SyntaxKind, TextRange};
+
+use crate::{AssistContext, AssistId, AssistKind, Assists};
+
+// Assist: remove_parentheses
+//
+// Removes useless parentheses.
+//
+// ```
+// fn main() {
+//     _ = $0(2) + 2;
+// }
+// ```
+// ->
+// ```
+// fn main() {
+//     _ = 2 + 2;
+// }
+// ```
+pub(crate) fn remove_parentheses(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<()> {
+    let parens = ctx.find_node_at_offset::<ast::ParenExpr>()?;
+    let l_paren = parens.l_paren_token()?;
+    let r_paren = parens.r_paren_token()?;
+
+    let cursor_in_range = l_paren.text_range().contains_range(ctx.selection_trimmed())
+        || r_paren.text_range().contains_range(ctx.selection_trimmed());
+    if !cursor_in_range {
+        return None;
+    }
+
+    // FIXME: check that precedence is right
+
+    let delete_from_l = l_paren.text_range().start();
+    let delete_to_l = match l_paren.next_token() {
+        Some(it) if it.kind() == SyntaxKind::WHITESPACE => it.text_range().end(),
+        _ => l_paren.text_range().end(),
+    };
+
+    let delete_from_r = match r_paren.prev_token() {
+        Some(it) if it.kind() == SyntaxKind::WHITESPACE => it.text_range().start(),
+        _ => r_paren.text_range().start(),
+    };
+    let delete_to_r = r_paren.text_range().end();
+
+    let target = parens.syntax().text_range();
+    acc.add(
+        AssistId("remove_parentheses", AssistKind::Refactor),
+        "Remove parentheses",
+        target,
+        |builder| {
+            builder.delete(TextRange::new(delete_from_l, delete_to_l));
+            builder.delete(TextRange::new(delete_from_r, delete_to_r));
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    #[test]
+    fn remove_parens_simple() {
+        check_assist(remove_parentheses, r#"fn f() { $0(2) + 2; }"#, r#"fn f() { 2 + 2; }"#);
+        check_assist(remove_parentheses, r#"fn f() { ($02) + 2; }"#, r#"fn f() { 2 + 2; }"#);
+        check_assist(remove_parentheses, r#"fn f() { (2)$0 + 2; }"#, r#"fn f() { 2 + 2; }"#);
+        check_assist(remove_parentheses, r#"fn f() { (2$0) + 2; }"#, r#"fn f() { 2 + 2; }"#);
+    }
+
+    // We should not permit assist here and yet
+    #[test]
+    fn remove_parens_wrong() {
+        check_assist(
+            remove_parentheses,
+            r#"fn f() { $0(2 + 2) * 8; }"#,
+            r#"fn f() { 2 + 2 * 8; }"#,
+        );
+    }
+
+    #[test]
+    fn remove_parens_doesnt_apply_with_cursor_not_on_paren() {
+        check_assist_not_applicable(remove_parentheses, r#"fn f() { (2 +$0 2) }"#);
+        check_assist_not_applicable(remove_parentheses, r#"fn f() {$0 (2 + 2) }"#);
+    }
+}

crates/ide-assists/src/lib.rs

@@ -179,6 +179,7 @@ mod handlers {
     mod remove_dbg;
     mod remove_mut;
     mod remove_unused_param;
+    mod remove_parentheses;
     mod reorder_fields;
     mod reorder_impl_items;
     mod replace_try_expr_with_match;
@@ -280,6 +281,7 @@ mod handlers {
             remove_dbg::remove_dbg,
             remove_mut::remove_mut,
             remove_unused_param::remove_unused_param,
+            remove_parentheses::remove_parentheses,
             reorder_fields::reorder_fields,
             reorder_impl_items::reorder_impl_items,
             replace_try_expr_with_match::replace_try_expr_with_match,

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

@@ -1978,6 +1978,23 @@ impl Walrus {
     )
 }
 
+#[test]
+fn doctest_remove_parentheses() {
+    check_doc_test(
+        "remove_parentheses",
+        r#####"
+fn main() {
+    _ = $0(2) + 2;
+}
+"#####,
+        r#####"
+fn main() {
+    _ = 2 + 2;
+}
+"#####,
+    )
+}
+
 #[test]
 fn doctest_remove_unused_param() {
     check_doc_test(