Merge commit '30448e8cf9' into clippyup
This commit is contained in:
Philipp Krones
parent
ec2c6155aa
commit
e6dc0efc00
114 changed files with 2970 additions and 653 deletions
234
clippy_lints/src/missing_fields_in_debug.rs
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234
clippy_lints/src/missing_fields_in_debug.rs
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@ -0,0 +1,234 @@
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use std::ops::ControlFlow;
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use clippy_utils::{
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diagnostics::span_lint_and_then,
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is_path_lang_item, paths,
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ty::match_type,
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visitors::{for_each_expr, Visitable},
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};
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use rustc_ast::LitKind;
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use rustc_data_structures::fx::FxHashSet;
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use rustc_hir::Block;
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use rustc_hir::{
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def::{DefKind, Res},
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Expr, ImplItemKind, LangItem, Node,
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};
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use rustc_hir::{ExprKind, Impl, ItemKind, QPath, TyKind};
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use rustc_hir::{ImplItem, Item, VariantData};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty::Ty;
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use rustc_middle::ty::TypeckResults;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::{sym, Span, Symbol};
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for manual [`core::fmt::Debug`](https://doc.rust-lang.org/core/fmt/trait.Debug.html) implementations that do not use all fields.
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///
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/// ### Why is this bad?
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/// A common mistake is to forget to update manual `Debug` implementations when adding a new field
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/// to a struct or a new variant to an enum.
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///
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/// At the same time, it also acts as a style lint to suggest using [`core::fmt::DebugStruct::finish_non_exhaustive`](https://doc.rust-lang.org/core/fmt/struct.DebugStruct.html#method.finish_non_exhaustive)
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/// for the times when the user intentionally wants to leave out certain fields (e.g. to hide implementation details).
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///
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/// ### Known problems
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/// This lint works based on the `DebugStruct` helper types provided by the `Formatter`,
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/// so this won't detect `Debug` impls that use the `write!` macro.
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/// Oftentimes there is more logic to a `Debug` impl if it uses `write!` macro, so it tries
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/// to be on the conservative side and not lint in those cases in an attempt to prevent false positives.
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///
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/// This lint also does not look through function calls, so calling a function does not consider fields
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/// used inside of that function as used by the `Debug` impl.
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///
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/// Lastly, it also ignores tuple structs as their `DebugTuple` formatter does not have a `finish_non_exhaustive`
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/// method, as well as enums because their exhaustiveness is already checked by the compiler when matching on the enum,
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/// making it much less likely to accidentally forget to update the `Debug` impl when adding a new variant.
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///
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/// ### Example
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/// ```rust
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/// use std::fmt;
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/// struct Foo {
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/// data: String,
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/// // implementation detail
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/// hidden_data: i32
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/// }
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/// impl fmt::Debug for Foo {
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/// fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
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/// formatter
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/// .debug_struct("Foo")
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/// .field("data", &self.data)
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/// .finish()
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/// }
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/// }
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/// ```
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/// Use instead:
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/// ```rust
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/// use std::fmt;
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/// struct Foo {
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/// data: String,
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/// // implementation detail
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/// hidden_data: i32
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/// }
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/// impl fmt::Debug for Foo {
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/// fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
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/// formatter
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/// .debug_struct("Foo")
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/// .field("data", &self.data)
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/// .finish_non_exhaustive()
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/// }
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/// }
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/// ```
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#[clippy::version = "1.70.0"]
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pub MISSING_FIELDS_IN_DEBUG,
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pedantic,
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"missing fields in manual `Debug` implementation"
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}
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declare_lint_pass!(MissingFieldsInDebug => [MISSING_FIELDS_IN_DEBUG]);
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fn report_lints(cx: &LateContext<'_>, span: Span, span_notes: Vec<(Span, &'static str)>) {
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span_lint_and_then(
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cx,
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MISSING_FIELDS_IN_DEBUG,
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span,
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"manual `Debug` impl does not include all fields",
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|diag| {
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for (span, note) in span_notes {
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diag.span_note(span, note);
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}
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diag.help("consider including all fields in this `Debug` impl")
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.help("consider calling `.finish_non_exhaustive()` if you intend to ignore fields");
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},
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);
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}
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/// Checks if we should lint in a block of code
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///
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/// The way we check for this condition is by checking if there is
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/// a call to `Formatter::debug_struct` but no call to `.finish_non_exhaustive()`.
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fn should_lint<'tcx>(
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cx: &LateContext<'tcx>,
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typeck_results: &TypeckResults<'tcx>,
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block: impl Visitable<'tcx>,
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) -> bool {
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// Is there a call to `DebugStruct::finish_non_exhaustive`? Don't lint if there is.
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let mut has_finish_non_exhaustive = false;
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// Is there a call to `DebugStruct::debug_struct`? Do lint if there is.
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let mut has_debug_struct = false;
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for_each_expr(block, |expr| {
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if let ExprKind::MethodCall(path, recv, ..) = &expr.kind {
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let recv_ty = typeck_results.expr_ty(recv).peel_refs();
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if path.ident.name == sym::debug_struct && match_type(cx, recv_ty, &paths::FORMATTER) {
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has_debug_struct = true;
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} else if path.ident.name == sym!(finish_non_exhaustive) && match_type(cx, recv_ty, &paths::DEBUG_STRUCT) {
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has_finish_non_exhaustive = true;
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}
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}
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ControlFlow::<!, _>::Continue(())
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});
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!has_finish_non_exhaustive && has_debug_struct
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}
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/// Checks if the given expression is a call to `DebugStruct::field`
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/// and the first argument to it is a string literal and if so, returns it
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///
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/// Example: `.field("foo", ....)` returns `Some("foo")`
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fn as_field_call<'tcx>(
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cx: &LateContext<'tcx>,
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typeck_results: &TypeckResults<'tcx>,
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expr: &Expr<'_>,
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) -> Option<Symbol> {
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if let ExprKind::MethodCall(path, recv, [debug_field, _], _) = &expr.kind
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&& let recv_ty = typeck_results.expr_ty(recv).peel_refs()
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&& match_type(cx, recv_ty, &paths::DEBUG_STRUCT)
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&& path.ident.name == sym::field
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&& let ExprKind::Lit(lit) = &debug_field.kind
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&& let LitKind::Str(sym, ..) = lit.node
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{
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Some(sym)
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} else {
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None
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}
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}
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/// Attempts to find unused fields assuming that the item is a struct
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fn check_struct<'tcx>(
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cx: &LateContext<'tcx>,
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typeck_results: &TypeckResults<'tcx>,
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block: &'tcx Block<'tcx>,
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self_ty: Ty<'tcx>,
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item: &'tcx Item<'tcx>,
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data: &VariantData<'_>,
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) {
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// Is there a "direct" field access anywhere (i.e. self.foo)?
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// We don't want to lint if there is not, because the user might have
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// a newtype struct and use fields from the wrapped type only.
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let mut has_direct_field_access = false;
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let mut field_accesses = FxHashSet::default();
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for_each_expr(block, |expr| {
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if let ExprKind::Field(target, ident) = expr.kind
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&& let target_ty = typeck_results.expr_ty_adjusted(target).peel_refs()
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&& target_ty == self_ty
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{
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field_accesses.insert(ident.name);
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has_direct_field_access = true;
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} else if let Some(sym) = as_field_call(cx, typeck_results, expr) {
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field_accesses.insert(sym);
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}
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ControlFlow::<!, _>::Continue(())
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});
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let span_notes = data
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.fields()
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.iter()
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.filter_map(|field| {
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if field_accesses.contains(&field.ident.name) || is_path_lang_item(cx, field.ty, LangItem::PhantomData) {
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None
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} else {
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Some((field.span, "this field is unused"))
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}
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})
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.collect::<Vec<_>>();
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// only lint if there's also at least one direct field access to allow patterns
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// where one might have a newtype struct and uses fields from the wrapped type
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if !span_notes.is_empty() && has_direct_field_access {
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report_lints(cx, item.span, span_notes);
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}
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}
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impl<'tcx> LateLintPass<'tcx> for MissingFieldsInDebug {
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fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx rustc_hir::Item<'tcx>) {
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// is this an `impl Debug for X` block?
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if let ItemKind::Impl(Impl { of_trait: Some(trait_ref), self_ty, items, .. }) = item.kind
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&& let Res::Def(DefKind::Trait, trait_def_id) = trait_ref.path.res
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&& let TyKind::Path(QPath::Resolved(_, self_path)) = &self_ty.kind
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&& cx.match_def_path(trait_def_id, &[sym::core, sym::fmt, sym::Debug])
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// don't trigger if this impl was derived
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&& !cx.tcx.has_attr(item.owner_id, sym::automatically_derived)
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&& !item.span.from_expansion()
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// find `Debug::fmt` function
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&& let Some(fmt_item) = items.iter().find(|i| i.ident.name == sym::fmt)
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&& let ImplItem { kind: ImplItemKind::Fn(_, body_id), .. } = cx.tcx.hir().impl_item(fmt_item.id)
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&& let body = cx.tcx.hir().body(*body_id)
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&& let ExprKind::Block(block, _) = body.value.kind
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// inspect `self`
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&& let self_ty = cx.tcx.type_of(self_path.res.def_id()).skip_binder().peel_refs()
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&& let Some(self_adt) = self_ty.ty_adt_def()
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&& let Some(self_def_id) = self_adt.did().as_local()
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&& let Some(Node::Item(self_item)) = cx.tcx.hir().find_by_def_id(self_def_id)
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// NB: can't call cx.typeck_results() as we are not in a body
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&& let typeck_results = cx.tcx.typeck_body(*body_id)
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&& should_lint(cx, typeck_results, block)
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{
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// we intentionally only lint structs, see lint description
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if let ItemKind::Struct(data, _) = &self_item.kind {
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check_struct(cx, typeck_results, block, self_ty, item, data);
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}
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}
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}
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}
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