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