From 805e51389ba89ad1460efafcf2e0a373008d72bc Mon Sep 17 00:00:00 2001
From: David Rubin <sinon@vortan.dev>
Date: Tue, 9 Jun 2026 18:37:12 -0700
Subject: [PATCH] Sema: catch missing @intCast case

---
 src/Sema.zig                                  |  2 +-
 test/cases/safety/@intCast negative to u0.zig | 22 +++++++++++++++++++
 ... to u0.zig => @intCast positive to u0.zig} |  0
 3 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 test/cases/safety/@intCast negative to u0.zig
 rename test/cases/safety/{@intCast to u0.zig => @intCast positive to u0.zig} (100%)

diff --git a/src/Sema.zig b/src/Sema.zig
index 431508292988b782c03b2d12beca356b829374ac..d5ca3362eff259d909c3cbd8236923ceab9291c6 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -9293,7 +9293,7 @@ fn intCast(
                     break :ok all_in_range;
                 } else ok: {
                     const zero_inst = Air.internedToRef((try pt.intValue(operand_ty, 0)).toIntern());
-                    const is_in_range = try block.addBinOp(.cmp_lte, operand, zero_inst);
+                    const is_in_range = try block.addBinOp(.cmp_eq, operand, zero_inst);
                     break :ok is_in_range;
                 };
                 try sema.addSafetyCheck(block, src, ok, .integer_out_of_bounds);
diff --git a/test/cases/safety/@intCast negative to u0.zig b/test/cases/safety/@intCast negative to u0.zig
new file mode 100644
index 0000000000000000000000000000000000000000..a445f755b7b8edb1e2a8f85375d92be95a8875aa
--- /dev/null
+++ b/test/cases/safety/@intCast negative to u0.zig	
@@ -0,0 +1,22 @@
+const std = @import("std");
+
+pub fn panic(message: []const u8, stack_trace: ?*std.builtin.StackTrace, _: ?usize) noreturn {
+    _ = stack_trace;
+    if (std.mem.eql(u8, message, "integer does not fit in destination type")) {
+        std.process.exit(0);
+    }
+    std.process.exit(1);
+}
+
+pub fn main() !void {
+    bar(1, -1);
+    return error.TestFailed;
+}
+
+fn bar(one: u1, not_zero: i32) void {
+    const x = one << @intCast(not_zero);
+    _ = x;
+}
+// run
+// backend=selfhosted,llvm
+// target=x86_64-linux,aarch64-linux
diff --git a/test/cases/safety/@intCast to u0.zig b/test/cases/safety/@intCast positive to u0.zig
similarity index 100%
rename from test/cases/safety/@intCast to u0.zig
rename to test/cases/safety/@intCast positive to u0.zig
-- 
2.54.0