assert that each block ends with an instruction which may do so

1 files changed, 9 insertions, 0 deletions

diff --git a/src/compile.zig b/src/compile.zig
index 0918d30..8cf61ca 100644
--- a/src/compile.zig
+++ b/src/compile.zig
@@ -66,6 +66,8 @@ pub const Instr = struct {
         true: BlockRef,
         false: BlockRef,
 
+        pub const may_end_block = {};
+
         pub fn sources(self: Branch) Sources {
             return Sources.fromSlice(&.{self.cond}) catch unreachable;
         }
@@ -74,12 +76,16 @@ pub const Instr = struct {
     pub const Jump = struct {
         to: BlockRef,
 
+        pub const may_end_block = {};
+
         pub fn sources(_: Jump) Sources {
             return Sources.init(0) catch unreachable;
         }
     };
 
     pub const Exit = struct {
+        pub const may_end_block = {};
+
         pub fn sources(_: Exit) Sources {
             return Sources.init(0) catch unreachable;
         }
@@ -164,6 +170,9 @@ pub const BasicBlock = struct {
             if (instr.dest()) |dest|
                 try self.vreg_last_use.put(allocator, dest, i);
         }
+        std.debug.assert(switch (self.instrs.items[self.instrs.items.len - 1].type) {
+            inline else => |ty| @hasDecl(@TypeOf(ty), "may_end_block"),
+        });
     }
 };