Reject negative literals for unsigned or char types in pattern ranges and literals

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

@@ -0,0 +1,24 @@
+#![feature(pattern_types)]
+#![feature(pattern_type_macro)]
+
+use std::pat::pattern_type;
+
+type Sign = pattern_type!(u32 is -10..);
+//~^ ERROR: cannot apply unary operator `-`
+
+type SignedChar = pattern_type!(char is -'A'..);
+//~^ ERROR: cannot apply unary operator `-`
+
+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 +1,41 @@
+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[E0600]: cannot apply unary operator `-` to type `u32`
+  --> $DIR/signed_ranges.rs:6:34
+   |
+LL | type Sign = pattern_type!(u32 is -10..);
+   |                                  ^^^ cannot apply unary operator `-`
+   |
+   = note: unsigned values cannot be negated
+
+error[E0600]: cannot apply unary operator `-` to type `char`
+  --> $DIR/signed_ranges.rs:9:41
+   |
+LL | type SignedChar = pattern_type!(char is -'A'..);
+   |                                         ^^^^ cannot apply unary operator `-`
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0277, E0600.
+For more information about an error, try `rustc --explain E0277`.