Merge commit '928e72dd10749875cbd412f74bfbfd7765dbcd8a' into clippyup
This commit is contained in:
flip1995
237
clippy_lints/src/default_numeric_fallback.rs
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237
clippy_lints/src/default_numeric_fallback.rs
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use rustc_ast::ast::{LitFloatType, LitIntType, LitKind};
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use rustc_errors::Applicability;
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use rustc_hir::{
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intravisit::{walk_expr, walk_stmt, NestedVisitorMap, Visitor},
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Body, Expr, ExprKind, HirId, Lit, Stmt, StmtKind,
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};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::{
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hir::map::Map,
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ty::{self, FloatTy, IntTy, PolyFnSig, Ty},
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};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use if_chain::if_chain;
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use crate::utils::{snippet, span_lint_and_sugg};
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declare_clippy_lint! {
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/// **What it does:** Checks for usage of unconstrained numeric literals which may cause default numeric fallback in type
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/// inference.
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///
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/// Default numeric fallback means that if numeric types have not yet been bound to concrete
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/// types at the end of type inference, then integer type is bound to `i32`, and similarly
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/// floating type is bound to `f64`.
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///
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/// See [RFC0212](https://github.com/rust-lang/rfcs/blob/master/text/0212-restore-int-fallback.md) for more information about the fallback.
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///
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/// **Why is this bad?** For those who are very careful about types, default numeric fallback
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/// can be a pitfall that cause unexpected runtime behavior.
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///
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/// **Known problems:** This lint can only be allowed at the function level or above.
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///
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/// **Example:**
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/// ```rust
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/// let i = 10;
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/// let f = 1.23;
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/// ```
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///
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/// Use instead:
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/// ```rust
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/// let i = 10i32;
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/// let f = 1.23f64;
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/// ```
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pub DEFAULT_NUMERIC_FALLBACK,
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restriction,
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"usage of unconstrained numeric literals which may cause default numeric fallback."
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}
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declare_lint_pass!(DefaultNumericFallback => [DEFAULT_NUMERIC_FALLBACK]);
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impl LateLintPass<'_> for DefaultNumericFallback {
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fn check_body(&mut self, cx: &LateContext<'tcx>, body: &'tcx Body<'_>) {
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let mut visitor = NumericFallbackVisitor::new(cx);
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visitor.visit_body(body);
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}
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}
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struct NumericFallbackVisitor<'a, 'tcx> {
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/// Stack manages type bound of exprs. The top element holds current expr type.
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ty_bounds: Vec<TyBound<'tcx>>,
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cx: &'a LateContext<'tcx>,
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}
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impl<'a, 'tcx> NumericFallbackVisitor<'a, 'tcx> {
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fn new(cx: &'a LateContext<'tcx>) -> Self {
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Self {
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ty_bounds: vec![TyBound::Nothing],
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cx,
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}
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}
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/// Check whether a passed literal has potential to cause fallback or not.
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fn check_lit(&self, lit: &Lit, lit_ty: Ty<'tcx>) {
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if_chain! {
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if let Some(ty_bound) = self.ty_bounds.last();
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if matches!(lit.node,
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LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::Float(_, LitFloatType::Unsuffixed));
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if !ty_bound.is_integral();
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then {
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let suffix = match lit_ty.kind() {
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ty::Int(IntTy::I32) => "i32",
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ty::Float(FloatTy::F64) => "f64",
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// Default numeric fallback never results in other types.
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_ => return,
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};
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let sugg = format!("{}_{}", snippet(self.cx, lit.span, ""), suffix);
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span_lint_and_sugg(
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self.cx,
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DEFAULT_NUMERIC_FALLBACK,
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lit.span,
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"default numeric fallback might occur",
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"consider adding suffix",
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sugg,
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Applicability::MaybeIncorrect,
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);
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}
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}
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}
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}
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impl<'a, 'tcx> Visitor<'tcx> for NumericFallbackVisitor<'a, 'tcx> {
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type Map = Map<'tcx>;
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#[allow(clippy::too_many_lines)]
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fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
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match &expr.kind {
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ExprKind::Call(func, args) => {
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if let Some(fn_sig) = fn_sig_opt(self.cx, func.hir_id) {
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for (expr, bound) in args.iter().zip(fn_sig.skip_binder().inputs().iter()) {
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// Push found arg type, then visit arg.
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self.ty_bounds.push(TyBound::Ty(bound));
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self.visit_expr(expr);
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self.ty_bounds.pop();
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}
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return;
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}
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},
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ExprKind::MethodCall(_, _, args, _) => {
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if let Some(def_id) = self.cx.typeck_results().type_dependent_def_id(expr.hir_id) {
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let fn_sig = self.cx.tcx.fn_sig(def_id).skip_binder();
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for (expr, bound) in args.iter().zip(fn_sig.inputs().iter()) {
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self.ty_bounds.push(TyBound::Ty(bound));
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self.visit_expr(expr);
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self.ty_bounds.pop();
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}
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return;
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}
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},
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ExprKind::Struct(qpath, fields, base) => {
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if_chain! {
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if let Some(def_id) = self.cx.qpath_res(qpath, expr.hir_id).opt_def_id();
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let ty = self.cx.tcx.type_of(def_id);
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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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then {
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let fields_def = &variant.fields;
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// Push field type then visit each field expr.
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for field in fields.iter() {
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let bound =
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fields_def
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.iter()
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.find_map(|f_def| {
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if f_def.ident == field.ident
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{ Some(self.cx.tcx.type_of(f_def.did)) }
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else { None }
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});
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self.ty_bounds.push(bound.into());
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self.visit_expr(field.expr);
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self.ty_bounds.pop();
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}
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// Visit base with no bound.
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if let Some(base) = base {
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self.ty_bounds.push(TyBound::Nothing);
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self.visit_expr(base);
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self.ty_bounds.pop();
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}
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return;
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}
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}
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},
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ExprKind::Lit(lit) => {
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let ty = self.cx.typeck_results().expr_ty(expr);
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self.check_lit(lit, ty);
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return;
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},
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_ => {},
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}
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walk_expr(self, expr);
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}
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fn visit_stmt(&mut self, stmt: &'tcx Stmt<'_>) {
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match stmt.kind {
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StmtKind::Local(local) => {
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if local.ty.is_some() {
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self.ty_bounds.push(TyBound::Any)
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} else {
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self.ty_bounds.push(TyBound::Nothing)
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}
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},
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_ => self.ty_bounds.push(TyBound::Nothing),
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}
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walk_stmt(self, stmt);
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self.ty_bounds.pop();
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}
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fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
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NestedVisitorMap::None
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}
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}
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fn fn_sig_opt<'tcx>(cx: &LateContext<'tcx>, hir_id: HirId) -> Option<PolyFnSig<'tcx>> {
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let node_ty = cx.typeck_results().node_type_opt(hir_id)?;
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// We can't use `TyS::fn_sig` because it automatically performs substs, this may result in FNs.
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match node_ty.kind() {
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ty::FnDef(def_id, _) => Some(cx.tcx.fn_sig(*def_id)),
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ty::FnPtr(fn_sig) => Some(*fn_sig),
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_ => None,
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}
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}
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#[derive(Debug, Clone, Copy)]
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enum TyBound<'tcx> {
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Any,
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Ty(Ty<'tcx>),
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Nothing,
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}
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impl<'tcx> TyBound<'tcx> {
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fn is_integral(self) -> bool {
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match self {
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TyBound::Any => true,
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TyBound::Ty(t) => t.is_integral(),
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TyBound::Nothing => false,
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}
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}
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}
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impl<'tcx> From<Option<Ty<'tcx>>> for TyBound<'tcx> {
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fn from(v: Option<Ty<'tcx>>) -> Self {
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match v {
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Some(t) => TyBound::Ty(t),
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None => TyBound::Nothing,
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}
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}
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}
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