Don't bother to save a block

Author: Nadrieril

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -1226,10 +1226,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             if let Some(last_otherwise_block) = otherwise_block {
                 last_otherwise_block
             } else {
-                // Any remaining candidates are unreachable.
-                if unmatched_candidates.is_empty() {
-                    return;
-                }
                 self.cfg.start_new_block()
             }
         } else {

tests/mir-opt/building/issue_101867.main.built.after.mir

@@ -27,13 +27,13 @@ fn main() -> () {
         StorageLive(_5);
         PlaceMention(_1);
         _6 = discriminant(_1);
-        switchInt(move _6) -> [1: bb5, otherwise: bb4];
+        switchInt(move _6) -> [1: bb6, otherwise: bb4];
     }
 
     bb1: {
         StorageLive(_3);
         StorageLive(_4);
-        _4 = begin_panic::<&str>(const "explicit panic") -> bb8;
+        _4 = begin_panic::<&str>(const "explicit panic") -> bb10;
     }
 
     bb2: {
@@ -48,27 +48,35 @@ fn main() -> () {
     }
 
     bb4: {
-        goto -> bb7;
+        goto -> bb9;
     }
 
     bb5: {
-        falseEdge -> [real: bb6, imaginary: bb4];
+        goto -> bb3;
     }
 
     bb6: {
+        falseEdge -> [real: bb8, imaginary: bb4];
+    }
+
+    bb7: {
+        goto -> bb4;
+    }
+
+    bb8: {
         _5 = ((_1 as Some).0: u8);
         _0 = const ();
         StorageDead(_5);
         StorageDead(_1);
         return;
     }
 
-    bb7: {
+    bb9: {
         StorageDead(_5);
         goto -> bb1;
     }
 
-    bb8 (cleanup): {
+    bb10 (cleanup): {
         resume;
     }
 }

tests/mir-opt/building/issue_49232.main.built.after.mir

@@ -17,15 +17,15 @@ fn main() -> () {
     }
 
     bb1: {
-        falseUnwind -> [real: bb2, unwind: bb12];
+        falseUnwind -> [real: bb2, unwind: bb14];
     }
 
     bb2: {
         StorageLive(_2);
         StorageLive(_3);
         _3 = const true;
         PlaceMention(_3);
-        switchInt(_3) -> [0: bb4, otherwise: bb5];
+        switchInt(_3) -> [0: bb4, otherwise: bb6];
     }
 
     bb3: {
@@ -34,51 +34,59 @@ fn main() -> () {
     }
 
     bb4: {
-        falseEdge -> [real: bb6, imaginary: bb5];
+        falseEdge -> [real: bb8, imaginary: bb6];
     }
 
     bb5: {
-        _0 = const ();
-        goto -> bb11;
+        goto -> bb3;
     }
 
     bb6: {
-        _2 = const 4_i32;
-        goto -> bb9;
+        _0 = const ();
+        goto -> bb13;
     }
 
     bb7: {
-        unreachable;
+        goto -> bb3;
     }
 
     bb8: {
-        goto -> bb9;
+        _2 = const 4_i32;
+        goto -> bb11;
     }
 
     bb9: {
+        unreachable;
+    }
+
+    bb10: {
+        goto -> bb11;
+    }
+
+    bb11: {
         FakeRead(ForLet(None), _2);
         StorageDead(_3);
         StorageLive(_5);
         StorageLive(_6);
         _6 = &_2;
-        _5 = std::mem::drop::<&i32>(move _6) -> [return: bb10, unwind: bb12];
+        _5 = std::mem::drop::<&i32>(move _6) -> [return: bb12, unwind: bb14];
     }
 
-    bb10: {
+    bb12: {
         StorageDead(_6);
         StorageDead(_5);
         _1 = const ();
         StorageDead(_2);
         goto -> bb1;
     }
 
-    bb11: {
+    bb13: {
         StorageDead(_3);
         StorageDead(_2);
         return;
     }
 
-    bb12 (cleanup): {
+    bb14 (cleanup): {
         resume;
     }
 }