From c1af3605328d21f59ee8ceba3c7350193f0a2429 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Tue, 18 Sep 2018 16:32:40 -0400
Subject: [PATCH] add compile error for slice.*.len

closes #1372
---
 src/ir.cpp              |  7 ++++++-
 test/compile_errors.zig | 10 ++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/ir.cpp b/src/ir.cpp
index 350459db23..0143445976 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -14874,8 +14874,13 @@ static ZigType *ir_analyze_instruction_field_ptr(IrAnalyze *ira, IrInstructionFi
     if (type_is_invalid(container_ptr->value.type))
         return ira->codegen->builtin_types.entry_invalid;
 
+    if (container_ptr->value.type->id != ZigTypeIdPointer) {
+        ir_add_error_node(ira, field_ptr_instruction->base.source_node,
+            buf_sprintf("attempt to dereference non-pointer type '%s'",
+                buf_ptr(&container_ptr->value.type->name)));
+        return ira->codegen->builtin_types.entry_invalid;
+    }
     ZigType *container_type = container_ptr->value.type->data.pointer.child_type;
-    assert(container_ptr->value.type->id == ZigTypeIdPointer);
 
     Buf *field_name = field_ptr_instruction->field_name_buffer;
     if (!field_name) {
diff --git a/test/compile_errors.zig b/test/compile_errors.zig
index a1dd33fb43..0b1446b518 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(
+        "deref slice and get len field",
+        \\export fn entry() void {
+        \\    var a: []u8 = undefined;
+        \\    _ = a.*.len;
+        \\}
+    ,
+        ".tmp_source.zig:3:12: error: attempt to dereference non-pointer type '[]u8'",
+    );
+
     cases.add(
         "@ptrCast a 0 bit type to a non- 0 bit type",
         \\export fn entry() bool {