New lint: default_numeric_fallback
This commit is contained in:
Yoshitomo Nakanishi
388
clippy_lints/src/default_numeric_fallback.rs
Normal file
388
clippy_lints/src/default_numeric_fallback.rs
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@@ -0,0 +1,388 @@
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use rustc_ast::ast::{Label, LitFloatType, LitIntType, LitKind};
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use rustc_hir::{
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self as hir,
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intravisit::{walk_expr, walk_stmt, walk_ty, FnKind, NestedVisitorMap, Visitor},
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Body, Expr, ExprKind, FnDecl, FnRetTy, Guard, 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, subst::GenericArgKind, FloatTy, IntTy, Ty, TyCtxt},
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};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::Span;
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use rustc_typeck::hir_ty_to_ty;
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use if_chain::if_chain;
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use crate::utils::span_lint_and_help;
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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:** None.
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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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fn enclosing_body_owner_opt(tcx: TyCtxt<'_>, hir_id: HirId) -> Option<HirId> {
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let hir_map = tcx.hir();
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for (parent, _) in hir_map.parent_iter(hir_id) {
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if let Some(body) = hir_map.maybe_body_owned_by(parent) {
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return Some(hir_map.body_owner(body));
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}
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}
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None
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}
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impl LateLintPass<'_> for DefaultNumericFallback {
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fn check_fn(
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&mut self,
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cx: &LateContext<'tcx>,
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_: FnKind<'tcx>,
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fn_decl: &'tcx FnDecl<'_>,
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body: &'tcx Body<'_>,
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_: Span,
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hir_id: HirId,
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) {
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let ret_ty_bound = match fn_decl.output {
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FnRetTy::DefaultReturn(_) => None,
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FnRetTy::Return(ty) => Some(ty),
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}
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.and_then(|ty| {
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let mut infer_ty_finder = InferTyFinder::new();
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infer_ty_finder.visit_ty(ty);
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if infer_ty_finder.found {
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None
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} else if enclosing_body_owner_opt(cx.tcx, hir_id).is_some() {
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cx.typeck_results().node_type_opt(ty.hir_id)
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} else {
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Some(hir_ty_to_ty(cx.tcx, ty))
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}
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});
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let mut visitor = NumericFallbackVisitor::new(ret_ty_bound, 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<Option<Ty<'tcx>>>,
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/// Ret type bound.
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ret_ty_bound: Option<Ty<'tcx>>,
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/// Break type bounds.
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break_ty_bounds: Vec<(Option<Label>, Option<Ty<'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(ret_ty_bound: Option<Ty<'tcx>>, cx: &'a LateContext<'tcx>) -> Self {
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Self {
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ty_bounds: vec![ret_ty_bound],
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ret_ty_bound,
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break_ty_bounds: vec![],
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cx,
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}
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}
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/// Check whether lit cause fallback or not.
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fn check_lit(&self, lit: &Lit, lit_ty: Ty<'tcx>) {
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let ty_bound = self.ty_bounds.last().unwrap();
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let should_lint = match (&lit.node, lit_ty.kind()) {
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(LitKind::Int(_, LitIntType::Unsuffixed), ty::Int(ty::IntTy::I32)) => {
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// In case integer literal is explicitly bound to i32, then suppress lint.
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ty_bound.map_or(true, |ty_bound| !matches!(ty_bound.kind(), ty::Int(IntTy::I32)))
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},
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(LitKind::Float(_, LitFloatType::Unsuffixed), ty::Float(ty::FloatTy::F64)) => {
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// In case float literal is explicitly bound to f64, then suppress lint.
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ty_bound.map_or(true, |ty_bound| !matches!(ty_bound.kind(), ty::Float(FloatTy::F64)))
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},
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_ => false,
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};
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if should_lint {
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span_lint_and_help(
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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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None,
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"consider adding suffix to avoid default numeric fallback",
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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, *self.ty_bounds.last().unwrap()) {
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(ExprKind::Array(_), Some(last_bound)) => {
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if let ty::Array(ty, _) = last_bound.kind() {
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self.ty_bounds.push(Some(ty))
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} else {
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self.ty_bounds.push(None)
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}
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},
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(ExprKind::Call(func, args), _) => {
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if_chain! {
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if let ExprKind::Path(ref func_path) = func.kind;
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if let Some(def_id) = self.cx.qpath_res(func_path, func.hir_id).opt_def_id();
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then {
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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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// Push found arg type, then visit arg.
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self.ty_bounds.push(Some(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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} else {
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self.ty_bounds.push(None)
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}
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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(Some(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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self.ty_bounds.push(None)
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},
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(ExprKind::Tup(exprs), Some(last_bound)) => {
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if let ty::Tuple(tys) = last_bound.kind() {
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for (expr, bound) in exprs.iter().zip(tys.iter()) {
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if let GenericArgKind::Type(ty) = bound.unpack() {
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self.ty_bounds.push(Some(ty));
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} else {
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self.ty_bounds.push(None);
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}
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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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self.ty_bounds.push(None)
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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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(ExprKind::If(cond, then, else_), last_bound) => {
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// Cond has no type bound in any situation.
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self.ty_bounds.push(None);
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self.visit_expr(cond);
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self.ty_bounds.pop();
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// Propagate current bound to childs.
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self.ty_bounds.push(last_bound);
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self.visit_expr(then);
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if let Some(else_) = else_ {
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self.visit_expr(else_);
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}
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self.ty_bounds.pop();
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return;
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},
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(ExprKind::Loop(_, label, ..), last_bound) => {
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self.break_ty_bounds.push((*label, last_bound));
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walk_expr(self, expr);
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self.break_ty_bounds.pop();
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return;
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},
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(ExprKind::Match(arg, arms, _), last_bound) => {
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// Match argument has no type bound.
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self.ty_bounds.push(None);
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self.visit_expr(arg);
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for arm in arms.iter() {
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self.visit_pat(arm.pat);
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if let Some(Guard::If(guard)) = arm.guard {
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self.visit_expr(guard);
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}
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}
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self.ty_bounds.pop();
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// Propagate current bound.
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self.ty_bounds.push(last_bound);
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for arm in arms.iter() {
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self.visit_expr(arm.body);
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}
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self.ty_bounds.pop();
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return;
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},
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(ExprKind::Block(..), last_bound) => self.ty_bounds.push(last_bound),
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(ExprKind::Break(destination, _), _) => {
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let ty = destination.label.map_or_else(
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|| self.break_ty_bounds.last().unwrap().1,
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|dest_label| {
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self.break_ty_bounds
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.iter()
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.rev()
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.find_map(|(loop_label, ty)| {
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loop_label.map_or(None, |loop_label| {
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if loop_label.ident == dest_label.ident {
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Some(*ty)
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} else {
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None
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}
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})
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})
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.unwrap()
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},
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);
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self.ty_bounds.push(ty);
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},
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(ExprKind::Ret(_), _) => self.ty_bounds.push(self.ret_ty_bound),
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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 field_ty =
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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(field_ty);
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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(None);
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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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self.ty_bounds.push(None);
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},
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_ => self.ty_bounds.push(None),
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}
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walk_expr(self, expr);
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self.ty_bounds.pop();
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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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let ty = local.ty.and_then(|hir_ty| {
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let mut infer_ty_finder = InferTyFinder::new();
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infer_ty_finder.visit_ty(hir_ty);
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if infer_ty_finder.found {
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None
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} else {
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self.cx.typeck_results().node_type_opt(hir_ty.hir_id)
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}
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});
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self.ty_bounds.push(ty);
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},
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_ => self.ty_bounds.push(None),
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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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/// Find `hir::TyKind::Infer` is included in passed typed.
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struct InferTyFinder {
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found: bool,
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}
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impl InferTyFinder {
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fn new() -> Self {
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Self { found: false }
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}
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}
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impl<'tcx> Visitor<'tcx> for InferTyFinder {
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type Map = Map<'tcx>;
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fn visit_ty(&mut self, ty: &'tcx hir::Ty<'_>) {
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match ty.kind {
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hir::TyKind::Infer => {
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self.found = true;
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},
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_ => {
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walk_ty(self, ty);
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},
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}
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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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