From b16229da1de90295b4d173f1a0ddbca677e8cdf2 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Mon, 17 Sep 2018 19:41:11 -0400
Subject: [PATCH] add compile error for @ptrCast 0 bit type to non-0 bit type

---
 src/ir.cpp              | 20 +++++++++++++++++---
 test/compile_errors.zig | 13 +++++++++++++
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/src/ir.cpp b/src/ir.cpp
index d073f3296..0cb09df01 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -11528,7 +11528,13 @@ static bool optional_value_is_null(ConstExprValue *val) {
 static ZigType *ir_analyze_bin_op_cmp(IrAnalyze *ira, IrInstructionBinOp *bin_op_instruction) {
     Error err;
     IrInstruction *op1 = bin_op_instruction->op1->other;
+    if (type_is_invalid(op1->value.type))
+        return ira->codegen->builtin_types.entry_invalid;
+
     IrInstruction *op2 = bin_op_instruction->op2->other;
+    if (type_is_invalid(op2->value.type))
+        return ira->codegen->builtin_types.entry_invalid;
+
     AstNode *source_node = bin_op_instruction->base.source_node;
 
     IrBinOp op_id = bin_op_instruction->op_id;
@@ -20190,11 +20196,19 @@ static ZigType *ir_analyze_instruction_ptr_cast(IrAnalyze *ira, IrInstructionPtr
             instruction->base.source_node, nullptr, ptr);
     casted_ptr->value.type = dest_type;
 
+    if (type_has_bits(dest_type) && !type_has_bits(src_type)) {
+        ErrorMsg *msg = ir_add_error(ira, &instruction->base,
+            buf_sprintf("'%s' and '%s' do not have the same in-memory representation",
+                buf_ptr(&src_type->name), buf_ptr(&dest_type->name)));
+        add_error_note(ira->codegen, msg, ptr->source_node,
+                buf_sprintf("'%s' has no in-memory bits", buf_ptr(&src_type->name)));
+        add_error_note(ira->codegen, msg, dest_type_value->source_node,
+                buf_sprintf("'%s' has in-memory bits", buf_ptr(&dest_type->name)));
+        return ira->codegen->builtin_types.entry_invalid;
+    }
+
     // Keep the bigger alignment, it can only help-
     // unless the target is zero bits.
-    if ((err = type_resolve(ira->codegen, dest_type, ResolveStatusZeroBitsKnown)))
-        return ira->codegen->builtin_types.entry_invalid;
-
     IrInstruction *result;
     if (src_align_bytes > dest_align_bytes && type_has_bits(dest_type)) {
         result = ir_align_cast(ira, casted_ptr, src_align_bytes, false);
diff --git a/test/compile_errors.zig b/test/compile_errors.zig
index d1e9f6d03..a1dd33fb4 100644
--- a/test/compile_errors.zig
+++ b/test/compile_errors.zig
@@ -1,6 +1,19 @@
 const tests = @import("tests.zig");
 
 pub fn addCases(cases: *tests.CompileErrorContext) void {
+    cases.add(
+        "@ptrCast a 0 bit type to a non- 0 bit type",
+        \\export fn entry() bool {
+        \\    var x: u0 = 0;
+        \\    const p = @ptrCast(?*u0, &x);
+        \\    return p == null;
+        \\}
+    ,
+        ".tmp_source.zig:3:15: error: '*u0' and '?*u0' do not have the same in-memory representation",
+        ".tmp_source.zig:3:31: note: '*u0' has no in-memory bits",
+        ".tmp_source.zig:3:24: note: '?*u0' has in-memory bits",
+    );
+
     cases.add(
         "comparing a non-optional pointer against null",
         \\export fn entry() void {