From ac0cda8df81d5dc7d782ad8a32c0e5b064dd24ec Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Thu, 13 Sep 2018 13:48:41 -0400
Subject: [PATCH] add compile error for merging non- error sets

closes #1509
---
 src/analyze.cpp         |  1 +
 src/ir.cpp              | 12 ++++++++++++
 test/compile_errors.zig | 13 +++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/src/analyze.cpp b/src/analyze.cpp
index 78d907970eaf..9a9e9a051352 100644
--- a/src/analyze.cpp
+++ b/src/analyze.cpp
@@ -4069,6 +4069,7 @@ static void define_local_param_variables(CodeGen *g, ZigFn *fn_table_entry) {
 }
 
 bool resolve_inferred_error_set(CodeGen *g, ZigType *err_set_type, AstNode *source_node) {
+    assert(err_set_type->id == ZigTypeIdErrorSet);
     ZigFn *infer_fn = err_set_type->data.error_set.infer_fn;
     if (infer_fn != nullptr) {
         if (infer_fn->anal_state == FnAnalStateInvalid) {
diff --git a/src/ir.cpp b/src/ir.cpp
index 3a94cdef38d4..b432facb3620 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -12469,10 +12469,22 @@ static ZigType *ir_analyze_merge_error_sets(IrAnalyze *ira, IrInstructionBinOp *
     if (type_is_invalid(op1_type))
         return ira->codegen->builtin_types.entry_invalid;
 
+    if (op1_type->id != ZigTypeIdErrorSet) {
+        ir_add_error(ira, instruction->op1,
+                buf_sprintf("expected error set type, found '%s'", buf_ptr(&op1_type->name)));
+        return ira->codegen->builtin_types.entry_invalid;
+    }
+
     ZigType *op2_type = ir_resolve_type(ira, instruction->op2->other);
     if (type_is_invalid(op2_type))
         return ira->codegen->builtin_types.entry_invalid;
 
+    if (op2_type->id != ZigTypeIdErrorSet) {
+        ir_add_error(ira, instruction->op2,
+                buf_sprintf("expected error set type, found '%s'", buf_ptr(&op2_type->name)));
+        return ira->codegen->builtin_types.entry_invalid;
+    }
+
     if (type_is_global_error_set(op1_type) ||
         type_is_global_error_set(op2_type))
     {
diff --git a/test/compile_errors.zig b/test/compile_errors.zig
index dda45a5897f0..8fb64e21e28c 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(
+        "non error sets used in merge error sets operator",
+        \\export fn foo() void {
+        \\    const Errors = u8 || u16;
+        \\}
+        \\export fn bar() void {
+        \\    const Errors = error{} || u16;
+        \\}
+    ,
+        ".tmp_source.zig:2:20: error: expected error set type, found 'u8'",
+        ".tmp_source.zig:5:31: error: expected error set type, found 'u16'",
+    );
+
     cases.add(
         "variable initialization compile error then referenced",
         \\fn Undeclared() type {