Revert "structural_match: non-structural-match ty closures"

Reverts rust-lang#73353

Author: spastorino

compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs

@@ -133,9 +133,6 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                     traits::NonStructuralMatchTy::Generator => {
                         "generators cannot be used in patterns".to_string()
                     }
-                    traits::NonStructuralMatchTy::Closure => {
-                        "closures cannot be used in patterns".to_string()
-                    }
                     traits::NonStructuralMatchTy::Param => {
                         bug!("use of a constant whose type is a parameter inside a pattern")
                     }

compiler/rustc_trait_selection/src/traits/structural_match.rs

@@ -19,7 +19,6 @@ pub enum NonStructuralMatchTy<'tcx> {
     Opaque,
     Generator,
     Projection,
-    Closure,
 }
 
 /// This method traverses the structure of `ty`, trying to find an
@@ -155,9 +154,6 @@ impl<'a, 'tcx> TypeVisitor<'tcx> for Search<'a, 'tcx> {
             ty::Generator(..) | ty::GeneratorWitness(..) => {
                 return ControlFlow::Break(NonStructuralMatchTy::Generator);
             }
-            ty::Closure(..) => {
-                return ControlFlow::Break(NonStructuralMatchTy::Closure);
-            }
             ty::RawPtr(..) => {
                 // structural-match ignores substructure of
                 // `*const _`/`*mut _`, so skip `super_visit_with`.
@@ -198,7 +194,7 @@ impl<'a, 'tcx> TypeVisitor<'tcx> for Search<'a, 'tcx> {
                 // First check all contained types and then tell the caller to continue searching.
                 return ty.super_visit_with(self);
             }
-            ty::Infer(_) | ty::Placeholder(_) | ty::Bound(..) => {
+            ty::Closure(..) | ty::Infer(_) | ty::Placeholder(_) | ty::Bound(..) => {
                 bug!("unexpected type during structural-match checking: {:?}", ty);
             }
             ty::Error(_) => {