1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::numeric_literal;
3 use clippy_utils::source::snippet_opt;
4 use if_chain::if_chain;
5 use rustc_ast::ast::{LitFloatType, LitIntType, LitKind};
6 use rustc_errors::Applicability;
8 intravisit::{walk_expr, walk_stmt, NestedVisitorMap, Visitor},
9 Body, Expr, ExprKind, HirId, Lit, Stmt, StmtKind,
11 use rustc_lint::{LateContext, LateLintPass, LintContext};
14 lint::in_external_macro,
15 ty::{self, FloatTy, IntTy, PolyFnSig, Ty},
17 use rustc_session::{declare_lint_pass, declare_tool_lint};
20 declare_clippy_lint! {
22 /// Checks for usage of unconstrained numeric literals which may cause default numeric fallback in type
25 /// Default numeric fallback means that if numeric types have not yet been bound to concrete
26 /// types at the end of type inference, then integer type is bound to `i32`, and similarly
27 /// floating type is bound to `f64`.
29 /// See [RFC0212](https://github.com/rust-lang/rfcs/blob/master/text/0212-restore-int-fallback.md) for more information about the fallback.
31 /// ### Why is this bad?
32 /// For those who are very careful about types, default numeric fallback
33 /// can be a pitfall that cause unexpected runtime behavior.
35 /// ### Known problems
36 /// This lint can only be allowed at the function level or above.
49 #[clippy::version = "1.52.0"]
50 pub DEFAULT_NUMERIC_FALLBACK,
52 "usage of unconstrained numeric literals which may cause default numeric fallback."
55 declare_lint_pass!(DefaultNumericFallback => [DEFAULT_NUMERIC_FALLBACK]);
57 impl<'tcx> LateLintPass<'tcx> for DefaultNumericFallback {
58 fn check_body(&mut self, cx: &LateContext<'tcx>, body: &'tcx Body<'_>) {
59 let mut visitor = NumericFallbackVisitor::new(cx);
60 visitor.visit_body(body);
64 struct NumericFallbackVisitor<'a, 'tcx> {
65 /// Stack manages type bound of exprs. The top element holds current expr type.
66 ty_bounds: Vec<TyBound<'tcx>>,
68 cx: &'a LateContext<'tcx>,
71 impl<'a, 'tcx> NumericFallbackVisitor<'a, 'tcx> {
72 fn new(cx: &'a LateContext<'tcx>) -> Self {
74 ty_bounds: vec![TyBound::Nothing],
79 /// Check whether a passed literal has potential to cause fallback or not.
80 fn check_lit(&self, lit: &Lit, lit_ty: Ty<'tcx>) {
82 if !in_external_macro(self.cx.sess(), lit.span);
83 if let Some(ty_bound) = self.ty_bounds.last();
85 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::Float(_, LitFloatType::Unsuffixed));
86 if !ty_bound.is_numeric();
88 let (suffix, is_float) = match lit_ty.kind() {
89 ty::Int(IntTy::I32) => ("i32", false),
90 ty::Float(FloatTy::F64) => ("f64", true),
91 // Default numeric fallback never results in other types.
95 let src = if let Some(src) = snippet_opt(self.cx, lit.span) {
99 LitKind::Int(src, _) => format!("{}", src),
100 LitKind::Float(src, _) => format!("{}", src),
104 let sugg = numeric_literal::format(&src, Some(suffix), is_float);
107 DEFAULT_NUMERIC_FALLBACK,
109 "default numeric fallback might occur",
110 "consider adding suffix",
112 Applicability::MaybeIncorrect,
119 impl<'a, 'tcx> Visitor<'tcx> for NumericFallbackVisitor<'a, 'tcx> {
120 type Map = Map<'tcx>;
122 #[allow(clippy::too_many_lines)]
123 fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
125 ExprKind::Call(func, args) => {
126 if let Some(fn_sig) = fn_sig_opt(self.cx, func.hir_id) {
127 for (expr, bound) in iter::zip(*args, fn_sig.skip_binder().inputs()) {
128 // Push found arg type, then visit arg.
129 self.ty_bounds.push(TyBound::Ty(bound));
130 self.visit_expr(expr);
131 self.ty_bounds.pop();
137 ExprKind::MethodCall(_, _, args, _) => {
138 if let Some(def_id) = self.cx.typeck_results().type_dependent_def_id(expr.hir_id) {
139 let fn_sig = self.cx.tcx.fn_sig(def_id).skip_binder();
140 for (expr, bound) in iter::zip(*args, fn_sig.inputs()) {
141 self.ty_bounds.push(TyBound::Ty(bound));
142 self.visit_expr(expr);
143 self.ty_bounds.pop();
149 ExprKind::Struct(_, fields, base) => {
150 let ty = self.cx.typeck_results().expr_ty(expr);
152 if let Some(adt_def) = ty.ty_adt_def();
153 if adt_def.is_struct();
154 if let Some(variant) = adt_def.variants.iter().next();
156 let fields_def = &variant.fields;
158 // Push field type then visit each field expr.
159 for field in fields.iter() {
164 if f_def.ident(self.cx.tcx) == field.ident
165 { Some(self.cx.tcx.type_of(f_def.did)) }
168 self.ty_bounds.push(bound.into());
169 self.visit_expr(field.expr);
170 self.ty_bounds.pop();
173 // Visit base with no bound.
174 if let Some(base) = base {
175 self.ty_bounds.push(TyBound::Nothing);
176 self.visit_expr(base);
177 self.ty_bounds.pop();
184 ExprKind::Lit(lit) => {
185 let ty = self.cx.typeck_results().expr_ty(expr);
186 self.check_lit(lit, ty);
193 walk_expr(self, expr);
196 fn visit_stmt(&mut self, stmt: &'tcx Stmt<'_>) {
198 StmtKind::Local(local) => {
199 if local.ty.is_some() {
200 self.ty_bounds.push(TyBound::Any);
202 self.ty_bounds.push(TyBound::Nothing);
206 _ => self.ty_bounds.push(TyBound::Nothing),
209 walk_stmt(self, stmt);
210 self.ty_bounds.pop();
213 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
214 NestedVisitorMap::None
218 fn fn_sig_opt<'tcx>(cx: &LateContext<'tcx>, hir_id: HirId) -> Option<PolyFnSig<'tcx>> {
219 let node_ty = cx.typeck_results().node_type_opt(hir_id)?;
220 // We can't use `TyS::fn_sig` because it automatically performs substs, this may result in FNs.
221 match node_ty.kind() {
222 ty::FnDef(def_id, _) => Some(cx.tcx.fn_sig(*def_id)),
223 ty::FnPtr(fn_sig) => Some(*fn_sig),
228 #[derive(Debug, Clone, Copy)]
235 impl<'tcx> TyBound<'tcx> {
236 fn is_numeric(self) -> bool {
238 TyBound::Any => true,
239 TyBound::Ty(t) => t.is_numeric(),
240 TyBound::Nothing => false,
245 impl<'tcx> From<Option<Ty<'tcx>>> for TyBound<'tcx> {
246 fn from(v: Option<Ty<'tcx>>) -> Self {
248 Some(t) => TyBound::Ty(t),
249 None => TyBound::Nothing,