diff --git a/src-self-hosted/Module.zig b/src-self-hosted/Module.zig
index 24dcb541b4..c4b0f70d5c 100644
--- a/src-self-hosted/Module.zig
+++ b/src-self-hosted/Module.zig
@@ -2801,6 +2801,12 @@ pub fn resolvePeerTypes(self: *Module, scope: *Scope, instructions: []*Inst) !Ty
             prev_inst = next_inst;
             continue;
         }
+        if (next_inst.ty.zigTypeTag() == .Undefined)
+            continue;
+        if (prev_inst.ty.zigTypeTag() == .Undefined) {
+            prev_inst = next_inst;
+            continue;
+        }
         if (prev_inst.ty.isInt() and
             next_inst.ty.isInt() and
             prev_inst.ty.isSignedInt() == next_inst.ty.isSignedInt())
diff --git a/src-self-hosted/type.zig b/src-self-hosted/type.zig
index a9a1acf44b..66a7961073 100644
--- a/src-self-hosted/type.zig
+++ b/src-self-hosted/type.zig
@@ -163,7 +163,7 @@ pub const Type = extern union {
                 // Hot path for common case:
                 if (a.castPointer()) |a_payload| {
                     if (b.castPointer()) |b_payload| {
-                        return eql(a_payload.pointee_type, b_payload.pointee_type);
+                        return a.tag() == b.tag() and eql(a_payload.pointee_type, b_payload.pointee_type);
                     }
                 }
                 const is_slice_a = isSlice(a);
@@ -189,7 +189,7 @@ pub const Type = extern union {
             .Array => {
                 if (a.arrayLen() != b.arrayLen())
                     return false;
-                if (a.elemType().eql(b.elemType()))
+                if (!a.elemType().eql(b.elemType()))
                     return false;
                 const sentinel_a = a.arraySentinel();
                 const sentinel_b = b.arraySentinel();
@@ -501,9 +501,9 @@ pub const Type = extern union {
                 .noreturn,
                 => return out_stream.writeAll(@tagName(t)),
 
-                .enum_literal => return out_stream.writeAll("@TypeOf(.EnumLiteral)"),
-                .@"null" => return out_stream.writeAll("@TypeOf(null)"),
-                .@"undefined" => return out_stream.writeAll("@TypeOf(undefined)"),
+                .enum_literal => return out_stream.writeAll("@Type(.EnumLiteral)"),
+                .@"null" => return out_stream.writeAll("@Type(.Null)"),
+                .@"undefined" => return out_stream.writeAll("@Type(.Undefined)"),
 
                 .@"anyframe" => return out_stream.writeAll("anyframe"),
                 .anyerror_void_error_union => return out_stream.writeAll("anyerror!void"),
diff --git a/src-self-hosted/value.zig b/src-self-hosted/value.zig
index bfd205f4d9..b65aa06bea 100644
--- a/src-self-hosted/value.zig
+++ b/src-self-hosted/value.zig
@@ -301,15 +301,15 @@ pub const Value = extern union {
             .comptime_int_type => return out_stream.writeAll("comptime_int"),
             .comptime_float_type => return out_stream.writeAll("comptime_float"),
             .noreturn_type => return out_stream.writeAll("noreturn"),
-            .null_type => return out_stream.writeAll("@TypeOf(null)"),
-            .undefined_type => return out_stream.writeAll("@TypeOf(undefined)"),
+            .null_type => return out_stream.writeAll("@Type(.Null)"),
+            .undefined_type => return out_stream.writeAll("@Type(.Undefined)"),
             .fn_noreturn_no_args_type => return out_stream.writeAll("fn() noreturn"),
             .fn_void_no_args_type => return out_stream.writeAll("fn() void"),
             .fn_naked_noreturn_no_args_type => return out_stream.writeAll("fn() callconv(.Naked) noreturn"),
             .fn_ccc_void_no_args_type => return out_stream.writeAll("fn() callconv(.C) void"),
             .single_const_pointer_to_comptime_int_type => return out_stream.writeAll("*const comptime_int"),
             .const_slice_u8_type => return out_stream.writeAll("[]const u8"),
-            .enum_literal_type => return out_stream.writeAll("@TypeOf(.EnumLiteral)"),
+            .enum_literal_type => return out_stream.writeAll("@Type(.EnumLiteral)"),
             .anyframe_type => return out_stream.writeAll("anyframe"),
 
             .null_value => return out_stream.writeAll("null"),
diff --git a/src-self-hosted/zir_sema.zig b/src-self-hosted/zir_sema.zig
index 676b662077..88a130c1db 100644
--- a/src-self-hosted/zir_sema.zig
+++ b/src-self-hosted/zir_sema.zig
@@ -1239,6 +1239,12 @@ fn analyzeInstArithmetic(mod: *Module, scope: *Scope, inst: *zir.Inst.BinOp) Inn
 
     if (casted_lhs.value()) |lhs_val| {
         if (casted_rhs.value()) |rhs_val| {
+            if (lhs_val.isUndef() or rhs_val.isUndef()) {
+                return mod.constInst(scope, inst.base.src, .{
+                    .ty = resolved_type,
+                    .val = Value.initTag(.undef),
+                });
+            }
             return analyzeInstComptimeOp(mod, scope, scalar_type, inst, lhs_val, rhs_val);
         }
     }