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