Only allow negation on literals in patterns if it's on integers or floats

Author: oli-obk

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -31,7 +31,7 @@ use rustc_errors::{
 };
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, Namespace, Res};
 use rustc_hir::def_id::{DefId, LocalDefId};
-use rustc_hir::{self as hir, AnonConst, GenericArg, GenericArgs, HirId};
+use rustc_hir::{self as hir, AnonConst, GenericArg, GenericArgs, HirId, LangItem};
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::ObligationCause;
 use rustc_middle::middle::stability::AllowUnstable;
@@ -46,6 +46,7 @@ use rustc_middle::{bug, span_bug};
 use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw};
+use rustc_trait_selection::error_reporting::InferCtxtErrorExt as _;
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::wf::object_region_bounds;
 use rustc_trait_selection::traits::{self, ObligationCtxt};
@@ -2457,6 +2458,35 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                                 hir::PatExprKind::Lit { lit, negated } => {
                                     let lit_input =
                                         LitToConstInput { lit: &lit.node, ty, neg: negated };
+                                    let mut ty = ty;
+                                    if negated {
+                                        let infcx_;
+                                        let infcx = match self.infcx() {
+                                            Some(infcx) => infcx,
+                                            None => {
+                                                assert!(!ty.has_infer());
+                                                infcx_ = tcx
+                                                    .infer_ctxt()
+                                                    .ignoring_regions()
+                                                    .build(TypingMode::non_body_analysis());
+                                                &infcx_
+                                            }
+                                        };
+                                        let ocx = ObligationCtxt::new_with_diagnostics(infcx);
+                                        ocx.register_bound(
+                                            ObligationCause::dummy_with_span(expr.span),
+                                            self.tcx().param_env(self.item_def_id()),
+                                            ty,
+                                            self.tcx()
+                                                .require_lang_item(LangItem::Neg, Some(expr.span)),
+                                        );
+                                        let errors = ocx.select_all_or_error();
+                                        if !errors.is_empty() {
+                                            let guar =
+                                                infcx.err_ctxt().report_fulfillment_errors(errors);
+                                            ty = Ty::new_error(tcx, guar);
+                                        }
+                                    }
                                     let ct = tcx.lit_to_const(lit_input);
                                     (ct, ty)
                                 }

compiler/rustc_hir_typeck/src/pat.rs

@@ -570,8 +570,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
     fn check_pat_expr_unadjusted(&self, lt: &'tcx hir::PatExpr<'tcx>) -> Ty<'tcx> {
         let ty = match &lt.kind {
-            rustc_hir::PatExprKind::Lit { lit, .. } => {
-                self.check_expr_lit(lit, Expectation::NoExpectation)
+            rustc_hir::PatExprKind::Lit { lit, negated } => {
+                let ty = self.check_expr_lit(lit, Expectation::NoExpectation);
+                if *negated {
+                    self.register_bound(
+                        ty,
+                        self.tcx.require_lang_item(LangItem::Neg, Some(lt.span)),
+                        ObligationCause::dummy_with_span(lt.span),
+                    );
+                }
+                ty
             }
             rustc_hir::PatExprKind::ConstBlock(c) => {
                 self.check_expr_const_block(c, Expectation::NoExpectation)

tests/ui/type/pattern_types/signed_ranges.rs

@@ -1,22 +1,24 @@
 #![feature(pattern_types)]
 #![feature(pattern_type_macro)]
 
-//@ check-pass
-
 use std::pat::pattern_type;
 
 type Sign = pattern_type!(u32 is -10..);
+//~^ ERROR `u32: Neg` is not satisfied
 
 type SignedChar = pattern_type!(char is -'A'..);
+//~^ ERROR `char: Neg` is not satisfied
 
 fn main() {
     match 42_u8 {
         -10..253 => {}
+        //~^ ERROR `u8: Neg` is not satisfied
         _ => {}
     }
 
     match 'A' {
         -'\0'..'a' => {}
+        //~^ ERROR `char: Neg` is not satisfied
         _ => {}
     }
 }

tests/ui/type/pattern_types/signed_ranges.stderr

@@ -0,0 +1,49 @@
+error[E0277]: the trait bound `u32: Neg` is not satisfied
+  --> $DIR/signed_ranges.rs:6:34
+   |
+LL | type Sign = pattern_type!(u32 is -10..);
+   |                                  ^^^ the trait `Neg` is not implemented for `u32`
+   |
+   = help: the following other types implement trait `Neg`:
+             &f128
+             &f16
+             &f32
+             &f64
+             &i128
+             &i16
+             &i32
+             &i64
+           and 12 others
+
+error[E0277]: the trait bound `char: Neg` is not satisfied
+  --> $DIR/signed_ranges.rs:9:41
+   |
+LL | type SignedChar = pattern_type!(char is -'A'..);
+   |                                         ^^^^ the trait `Neg` is not implemented for `char`
+
+error[E0277]: the trait bound `u8: Neg` is not satisfied
+  --> $DIR/signed_ranges.rs:14:9
+   |
+LL |         -10..253 => {}
+   |         ^^^ the trait `Neg` is not implemented for `u8`
+   |
+   = help: the following other types implement trait `Neg`:
+             &f128
+             &f16
+             &f32
+             &f64
+             &i128
+             &i16
+             &i32
+             &i64
+           and 12 others
+
+error[E0277]: the trait bound `char: Neg` is not satisfied
+  --> $DIR/signed_ranges.rs:20:9
+   |
+LL |         -'\0'..'a' => {}
+   |         ^^^^^ the trait `Neg` is not implemented for `char`
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0277`.