Sema: resolve lazy values in resolveMaybeUndefValIntable

Closes #12512
Closes #12513

Author: Vexu

src/Sema.zig

@@ -1698,7 +1698,10 @@ fn resolveMaybeUndefValIntable(
         .elem_ptr => check = check.castTag(.elem_ptr).?.data.array_ptr,
         .eu_payload_ptr, .opt_payload_ptr => check = check.cast(Value.Payload.PayloadPtr).?.data.container_ptr,
         .generic_poison => return error.GenericPoison,
-        else => return val,
+        else => {
+            try sema.resolveLazyValue(block, src, val);
+            return val;
+        },
     };
 }
 

test/behavior/eval.zig

@@ -1325,3 +1325,25 @@ test "value in if block is comptime known" {
     };
     comptime try expect(std.mem.eql(u8, first, second));
 }
+
+test "lazy sizeof is resolved in division" {
+    const A = struct {
+        a: u32,
+    };
+    const a = 2;
+    try expect(@sizeOf(A) / a == 2);
+    try expect(@sizeOf(A) - a == 2);
+}
+
+test "lazy value is resolved as slice operand" {
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
+
+    const A = struct { a: u32 };
+    var a: [512]u64 = undefined;
+
+    const ptr1 = a[0..@sizeOf(A)];
+    const ptr2 = @ptrCast([*]u8, &a)[0..@sizeOf(A)];
+    try expect(@ptrToInt(ptr1) == @ptrToInt(ptr2));
+    try expect(ptr1.len == ptr2.len);
+}