From 78a9a465a372d25ef6f9a1f6bb1018160b8c94e1 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Mon, 17 Sep 2018 18:58:50 -0400
Subject: [PATCH] add compile error for non-optional types compared against
 null

closes #1539
---
 src/ir.cpp              |  3 +++
 test/compile_errors.zig | 10 ++++++++++
 2 files changed, 13 insertions(+)

diff --git a/src/ir.cpp b/src/ir.cpp
index e2bcbcffee..d073f3296c 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -11571,6 +11571,9 @@ static ZigType *ir_analyze_bin_op_cmp(IrAnalyze *ira, IrInstructionBinOp *bin_op
             ir_link_new_instruction(is_non_null, &bin_op_instruction->base);
         }
         return ira->codegen->builtin_types.entry_bool;
+    } else if (op1->value.type->id == ZigTypeIdNull || op2->value.type->id == ZigTypeIdNull) {
+        ir_add_error_node(ira, source_node, buf_sprintf("comparison against null can only be done with optionals"));
+        return ira->codegen->builtin_types.entry_invalid;
     }
 
     if (op1->value.type->id == ZigTypeIdErrorSet && op2->value.type->id == ZigTypeIdErrorSet) {
diff --git a/test/compile_errors.zig b/test/compile_errors.zig
index 40afc6df2d..d1e9f6d03a 100644
--- a/test/compile_errors.zig
+++ b/test/compile_errors.zig
@@ -1,6 +1,16 @@
 const tests = @import("tests.zig");
 
 pub fn addCases(cases: *tests.CompileErrorContext) void {
+    cases.add(
+        "comparing a non-optional pointer against null",
+        \\export fn entry() void {
+        \\    var x: i32 = 1;
+        \\    _ = &x == null;
+        \\}
+    ,
+        ".tmp_source.zig:3:12: error: comparison against null can only be done with optionals",
+    );
+
     cases.add(
         "non error sets used in merge error sets operator",
         \\export fn foo() void {