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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet;
use if_chain::if_chain;
use rustc_data_structures::fx::FxHashMap;
use rustc_errors::Applicability;
use rustc_hir::{self as hir, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::symbol::Symbol;
use std::fmt::Write as _;
declare_clippy_lint! {
/// ### What it does
/// Checks for struct constructors where all fields are shorthand and
/// the order of the field init shorthand in the constructor is inconsistent
/// with the order in the struct definition.
///
/// ### Why is this bad?
/// Since the order of fields in a constructor doesn't affect the
/// resulted instance as the below example indicates,
///
/// ```rust
/// #[derive(Debug, PartialEq, Eq)]
/// struct Foo {
/// x: i32,
/// y: i32,
/// }
/// let x = 1;
/// let y = 2;
///
/// // This assertion never fails:
/// assert_eq!(Foo { x, y }, Foo { y, x });
/// ```
///
/// inconsistent order can be confusing and decreases readability and consistency.
///
/// ### Example
/// ```rust
/// struct Foo {
/// x: i32,
/// y: i32,
/// }
/// let x = 1;
/// let y = 2;
///
/// Foo { y, x };
/// ```
///
/// Use instead:
/// ```rust
/// # struct Foo {
/// # x: i32,
/// # y: i32,
/// # }
/// # let x = 1;
/// # let y = 2;
/// Foo { x, y };
/// ```
#[clippy::version = "1.52.0"]
pub INCONSISTENT_STRUCT_CONSTRUCTOR,
pedantic,
"the order of the field init shorthand is inconsistent with the order in the struct definition"
}
declare_lint_pass!(InconsistentStructConstructor => [INCONSISTENT_STRUCT_CONSTRUCTOR]);
impl<'tcx> LateLintPass<'tcx> for InconsistentStructConstructor {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
if_chain! {
if !expr.span.from_expansion();
if let ExprKind::Struct(qpath, fields, base) = expr.kind;
let ty = cx.typeck_results().expr_ty(expr);
if let Some(adt_def) = ty.ty_adt_def();
if adt_def.is_struct();
if let Some(variant) = adt_def.variants().iter().next();
if fields.iter().all(|f| f.is_shorthand);
then {
let mut def_order_map = FxHashMap::default();
for (idx, field) in variant.fields.iter().enumerate() {
def_order_map.insert(field.name, idx);
}
if is_consistent_order(fields, &def_order_map) {
return;
}
let mut ordered_fields: Vec<_> = fields.iter().map(|f| f.ident.name).collect();
ordered_fields.sort_unstable_by_key(|id| def_order_map[id]);
let mut fields_snippet = String::new();
let (last_ident, idents) = ordered_fields.split_last().unwrap();
for ident in idents {
let _ = write!(fields_snippet, "{ident}, ");
}
fields_snippet.push_str(&last_ident.to_string());
let base_snippet = if let Some(base) = base {
format!(", ..{}", snippet(cx, base.span, ".."))
} else {
String::new()
};
let sugg = format!("{} {{ {fields_snippet}{base_snippet} }}",
snippet(cx, qpath.span(), ".."),
);
span_lint_and_sugg(
cx,
INCONSISTENT_STRUCT_CONSTRUCTOR,
expr.span,
"struct constructor field order is inconsistent with struct definition field order",
"try",
sugg,
Applicability::MachineApplicable,
)
}
}
}
}
// Check whether the order of the fields in the constructor is consistent with the order in the
// definition.
fn is_consistent_order<'tcx>(fields: &'tcx [hir::ExprField<'tcx>], def_order_map: &FxHashMap<Symbol, usize>) -> bool {
let mut cur_idx = usize::MIN;
for f in fields {
let next_idx = def_order_map[&f.ident.name];
if cur_idx > next_idx {
return false;
}
cur_idx = next_idx;
}
true
}
|
