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use clippy_utils::diagnostics::span_lint_hir_and_then;
use clippy_utils::source::snippet_opt;
use clippy_utils::{get_parent_node, numeric_literal};
use if_chain::if_chain;
use rustc_ast::ast::{LitFloatType, LitIntType, LitKind};
use rustc_errors::Applicability;
use rustc_hir::{
intravisit::{walk_expr, walk_stmt, Visitor},
Body, Expr, ExprKind, HirId, ItemKind, Lit, Node, Stmt, StmtKind,
};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::{
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;
/// ```
#[clippy::version = "1.52.0"]
pub DEFAULT_NUMERIC_FALLBACK,
restriction,
"usage of unconstrained numeric literals which may cause default numeric fallback."
}
declare_lint_pass!(DefaultNumericFallback => [DEFAULT_NUMERIC_FALLBACK]);
impl<'tcx> LateLintPass<'tcx> for DefaultNumericFallback {
fn check_body(&mut self, cx: &LateContext<'tcx>, body: &'tcx Body<'_>) {
let is_parent_const = if let Some(Node::Item(item)) = get_parent_node(cx.tcx, body.id().hir_id) {
matches!(item.kind, ItemKind::Const(..))
} else {
false
};
let mut visitor = NumericFallbackVisitor::new(cx, is_parent_const);
visitor.visit_body(body);
}
}
struct NumericFallbackVisitor<'a, 'tcx> {
/// Stack manages type bound of exprs. The top element holds current expr type.
ty_bounds: Vec<ExplicitTyBound>,
cx: &'a LateContext<'tcx>,
}
impl<'a, 'tcx> NumericFallbackVisitor<'a, 'tcx> {
fn new(cx: &'a LateContext<'tcx>, is_parent_const: bool) -> Self {
Self {
ty_bounds: vec![if is_parent_const {
ExplicitTyBound(true)
} else {
ExplicitTyBound(false)
}],
cx,
}
}
/// Check whether a passed literal has potential to cause fallback or not.
fn check_lit(&self, lit: &Lit, lit_ty: Ty<'tcx>, emit_hir_id: HirId) {
if_chain! {
if !in_external_macro(self.cx.sess(), lit.span);
if matches!(self.ty_bounds.last(), Some(ExplicitTyBound(false)));
if matches!(lit.node,
LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::Float(_, LitFloatType::Unsuffixed));
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_hir_and_then(
self.cx,
DEFAULT_NUMERIC_FALLBACK,
emit_hir_id,
lit.span,
"default numeric fallback might occur",
|diag| {
diag.span_suggestion(lit.span, "consider adding suffix", sugg, Applicability::MaybeIncorrect);
}
);
}
}
}
}
impl<'a, 'tcx> Visitor<'tcx> for NumericFallbackVisitor<'a, 'tcx> {
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((*bound).into());
self.visit_expr(expr);
self.ty_bounds.pop();
}
return;
}
},
ExprKind::MethodCall(_, receiver, 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(std::iter::once(*receiver).chain(args.iter()), fn_sig.inputs()) {
self.ty_bounds.push((*bound).into());
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(self.cx.tcx) == 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(ExplicitTyBound(false));
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, expr.hir_id);
return;
},
_ => {},
}
walk_expr(self, expr);
}
fn visit_stmt(&mut self, stmt: &'tcx Stmt<'_>) {
match stmt.kind {
// we cannot check the exact type since it's a hir::Ty which does not implement `is_numeric`
StmtKind::Local(local) => self.ty_bounds.push(ExplicitTyBound(local.ty.is_some())),
_ => self.ty_bounds.push(ExplicitTyBound(false)),
}
walk_stmt(self, stmt);
self.ty_bounds.pop();
}
}
fn fn_sig_opt<'tcx>(cx: &LateContext<'tcx>, hir_id: HirId) -> Option<PolyFnSig<'tcx>> {
let node_ty = cx.typeck_results().node_type_opt(hir_id)?;
// We can't use `Ty::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,
}
}
/// Wrapper around a `bool` to make the meaning of the value clearer
#[derive(Debug, Clone, Copy)]
struct ExplicitTyBound(pub bool);
impl<'tcx> From<Ty<'tcx>> for ExplicitTyBound {
fn from(v: Ty<'tcx>) -> Self {
Self(v.is_numeric())
}
}
impl<'tcx> From<Option<Ty<'tcx>>> for ExplicitTyBound {
fn from(v: Option<Ty<'tcx>>) -> Self {
Self(v.map_or(false, Ty::is_numeric))
}
}
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