Remove premature optimizations

Author: Nadrieril

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

@@ -998,14 +998,6 @@ impl ConstructorSet {
                     split.push(Single);
                 }
             }
-            ConstructorSet::Variants { variants, non_exhaustive } if seen.is_empty() => {
-                missing.extend(variants.iter().copied().map(Variant).filter(|ctor| {
-                    !(ctor.is_doc_hidden_variant(pcx) || ctor.is_unstable_variant(pcx))
-                }));
-                if *non_exhaustive {
-                    missing.push(NonExhaustive);
-                }
-            }
             ConstructorSet::Variants { variants, non_exhaustive } => {
                 let seen_set: FxHashSet<_> = seen.iter().map(|c| c.as_variant().unwrap()).collect();
                 let mut skipped_any_missing_variant = false;
@@ -1028,16 +1020,6 @@ impl ConstructorSet {
                     missing.push(NonExhaustive);
                 }
             }
-            ConstructorSet::Integers { range_1, range_2, non_exhaustive } if seen.is_empty() => {
-                if *non_exhaustive {
-                    missing.push(NonExhaustive);
-                } else {
-                    missing.push(IntRange(range_1.clone()));
-                    if let Some(range_2) = range_2 {
-                        missing.push(IntRange(range_2.clone()));
-                    }
-                }
-            }
             ConstructorSet::Integers { range_1, range_2, non_exhaustive } => {
                 let range = match range_2 {
                     None => SplitIntRange::Single(range_1.clone()),
@@ -1055,9 +1037,6 @@ impl ConstructorSet {
                     missing.push(NonExhaustive);
                 }
             }
-            &ConstructorSet::Slice(array_len) if seen.is_empty() => {
-                missing.push(Slice(Slice::new(array_len, VarLen(0, 0))));
-            }
             &ConstructorSet::Slice(array_len) => {
                 let seen_slices = seen.iter().map(|c| c.as_slice().unwrap()).map(|s| s.kind);
                 for (seen, splitted_slice) in SplitVarLenSlice::split(array_len, seen_slices) {