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//! Functionality for generating trivial constructors

use hir::StructKind;
use span::Edition;
use syntax::{
    ast::{make, Expr, Path},
    ToSmolStr,
};

/// given a type return the trivial constructor (if one exists)
pub fn use_trivial_constructor(
    db: &crate::RootDatabase,
    path: Path,
    ty: &hir::Type,
    edition: Edition,
) -> Option<Expr> {
    match ty.as_adt() {
        Some(hir::Adt::Enum(x)) => {
            if let &[variant] = &*x.variants(db) {
                if variant.kind(db) == hir::StructKind::Unit {
                    let path = make::path_qualified(
                        path,
                        make::path_segment(make::name_ref(
                            &variant.name(db).display_no_db(edition).to_smolstr(),
                        )),
                    );

                    return Some(make::expr_path(path));
                }
            }
        }
        Some(hir::Adt::Struct(x)) if x.kind(db) == StructKind::Unit => {
            return Some(make::expr_path(path));
        }
        _ => {}
    }

    None
}