Commit 13b36d458f

Andrew Kelley <superjoe30@gmail.com>
2018-02-01 16:23:25
*WIP* error sets - fix implicit cast
1 parent 5f518db
src/analyze.cpp
@@ -1274,7 +1274,7 @@ static bool type_allowed_in_extern(CodeGen *g, TypeTableEntry *type_entry) {
     zig_unreachable();
 }
 
-static TypeTableEntry *get_auto_err_set_type(CodeGen *g, FnTableEntry *fn_entry) {
+TypeTableEntry *get_auto_err_set_type(CodeGen *g, FnTableEntry *fn_entry) {
     TypeTableEntry *err_set_type = new_type_table_entry(TypeTableEntryIdErrorSet);
     buf_resize(&err_set_type->name, 0);
     buf_appendf(&err_set_type->name, "%s.errors", buf_ptr(&fn_entry->symbol_name));
@@ -3366,7 +3366,7 @@ void resolve_top_level_decl(CodeGen *g, Tld *tld, bool pointer_only, AstNode *so
     g->tld_ref_source_node_stack.pop();
 }
 
-bool types_match_const_cast_only(TypeTableEntry *expected_type, TypeTableEntry *actual_type) {
+bool types_match_const_cast_only(CodeGen *g, TypeTableEntry *expected_type, TypeTableEntry *actual_type) {
     if (expected_type == actual_type)
         return true;
 
@@ -3379,7 +3379,7 @@ bool types_match_const_cast_only(TypeTableEntry *expected_type, TypeTableEntry *
         actual_type->data.pointer.unaligned_bit_count == expected_type->data.pointer.unaligned_bit_count &&
         actual_type->data.pointer.alignment >= expected_type->data.pointer.alignment)
     {
-        return types_match_const_cast_only(expected_type->data.pointer.child_type,
+        return types_match_const_cast_only(g, expected_type->data.pointer.child_type,
                 actual_type->data.pointer.child_type);
     }
 
@@ -3397,7 +3397,7 @@ bool types_match_const_cast_only(TypeTableEntry *expected_type, TypeTableEntry *
             actual_ptr_type->data.pointer.unaligned_bit_count == expected_ptr_type->data.pointer.unaligned_bit_count &&
             actual_ptr_type->data.pointer.alignment >= expected_ptr_type->data.pointer.alignment)
         {
-            return types_match_const_cast_only(expected_ptr_type->data.pointer.child_type,
+            return types_match_const_cast_only(g, expected_ptr_type->data.pointer.child_type,
                     actual_ptr_type->data.pointer.child_type);
         }
     }
@@ -3406,7 +3406,7 @@ bool types_match_const_cast_only(TypeTableEntry *expected_type, TypeTableEntry *
     if (expected_type->id == TypeTableEntryIdMaybe &&
         actual_type->id == TypeTableEntryIdMaybe)
     {
-        return types_match_const_cast_only(
+        return types_match_const_cast_only(g,
                 expected_type->data.maybe.child_type,
                 actual_type->data.maybe.child_type);
     }
@@ -3415,14 +3415,43 @@ bool types_match_const_cast_only(TypeTableEntry *expected_type, TypeTableEntry *
     if (expected_type->id == TypeTableEntryIdErrorUnion &&
         actual_type->id == TypeTableEntryIdErrorUnion)
     {
-        return types_match_const_cast_only(
+        return types_match_const_cast_only(g,
                 expected_type->data.error_union.payload_type,
                 actual_type->data.error_union.payload_type) &&
-            types_match_const_cast_only(
+            types_match_const_cast_only(g,
                 expected_type->data.error_union.err_set_type,
                 actual_type->data.error_union.err_set_type);
     }
 
+    // error set
+    if (expected_type->id == TypeTableEntryIdErrorSet &&
+        actual_type->id == TypeTableEntryIdErrorSet)
+    {
+        TypeTableEntry *contained_set = actual_type;
+        TypeTableEntry *container_set = expected_type;
+
+        if (container_set == g->builtin_types.entry_global_error_set ||
+            container_set->data.error_set.infer_fn != nullptr)
+        {
+            return true;
+        }
+
+        ErrorTableEntry **errors = allocate<ErrorTableEntry *>(g->errors_by_index.length);
+        for (uint32_t i = 0; i < container_set->data.error_set.err_count; i += 1) {
+            ErrorTableEntry *error_entry = container_set->data.error_set.errors[i];
+            errors[error_entry->value] = error_entry;
+        }
+        for (uint32_t i = 0; i < contained_set->data.error_set.err_count; i += 1) {
+            ErrorTableEntry *contained_error_entry = contained_set->data.error_set.errors[i];
+            ErrorTableEntry *error_entry = errors[contained_error_entry->value];
+            if (error_entry == nullptr) {
+                return false;
+            }
+        }
+        free(errors);
+        return true;
+    }
+
     // fn
     if (expected_type->id == TypeTableEntryIdFn &&
         actual_type->id == TypeTableEntryIdFn)
@@ -3441,7 +3470,7 @@ bool types_match_const_cast_only(TypeTableEntry *expected_type, TypeTableEntry *
         }
         if (!expected_type->data.fn.is_generic &&
             actual_type->data.fn.fn_type_id.return_type->id != TypeTableEntryIdUnreachable &&
-            !types_match_const_cast_only(
+            !types_match_const_cast_only(g,
                 expected_type->data.fn.fn_type_id.return_type,
                 actual_type->data.fn.fn_type_id.return_type))
         {
@@ -3460,7 +3489,7 @@ bool types_match_const_cast_only(TypeTableEntry *expected_type, TypeTableEntry *
             FnTypeParamInfo *actual_param_info = &actual_type->data.fn.fn_type_id.param_info[i];
             FnTypeParamInfo *expected_param_info = &expected_type->data.fn.fn_type_id.param_info[i];
 
-            if (!types_match_const_cast_only(actual_param_info->type, expected_param_info->type)) {
+            if (!types_match_const_cast_only(g, actual_param_info->type, expected_param_info->type)) {
                 return false;
             }
 
src/analyze.hpp
@@ -46,7 +46,7 @@ bool type_has_bits(TypeTableEntry *type_entry);
 ImportTableEntry *add_source_file(CodeGen *g, PackageTableEntry *package, Buf *abs_full_path, Buf *source_code);
 
 
-bool types_match_const_cast_only(TypeTableEntry *expected_type, TypeTableEntry *actual_type);
+bool types_match_const_cast_only(CodeGen *g, TypeTableEntry *expected_type, TypeTableEntry *actual_type);
 VariableTableEntry *find_variable(CodeGen *g, Scope *orig_context, Buf *name);
 Tld *find_decl(CodeGen *g, Scope *scope, Buf *name);
 void resolve_top_level_decl(CodeGen *g, Tld *tld, bool pointer_only, AstNode *source_node);
@@ -189,5 +189,6 @@ ConstExprValue *get_builtin_value(CodeGen *codegen, const char *name);
 TypeTableEntry *get_ptr_to_stack_trace_type(CodeGen *g);
 void analyze_fn_body(CodeGen *g, FnTableEntry *fn_table_entry);
 
+TypeTableEntry *get_auto_err_set_type(CodeGen *g, FnTableEntry *fn_entry);
 
 #endif
src/ir.cpp
@@ -6375,7 +6375,7 @@ enum ImplicitCastMatchResult {
 static ImplicitCastMatchResult ir_types_match_with_implicit_cast(IrAnalyze *ira, TypeTableEntry *expected_type,
         TypeTableEntry *actual_type, IrInstruction *value)
 {
-    if (types_match_const_cast_only(expected_type, actual_type)) {
+    if (types_match_const_cast_only(ira->codegen, expected_type, actual_type)) {
         return ImplicitCastMatchResultYes;
     }
 
@@ -6412,13 +6412,6 @@ static ImplicitCastMatchResult ir_types_match_with_implicit_cast(IrAnalyze *ira,
         return ImplicitCastMatchResultYes;
     }
 
-    // implicit conversion from error set to another error set
-    if (expected_type->id == TypeTableEntryIdErrorSet &&
-        actual_type->id == TypeTableEntryIdErrorSet)
-    {
-        return ImplicitCastMatchResultYes;
-    }
-
     // implicit conversion from T to U!?T
     if (expected_type->id == TypeTableEntryIdErrorUnion &&
         expected_type->data.error_union.payload_type->id == TypeTableEntryIdMaybe &&
@@ -6463,7 +6456,7 @@ static ImplicitCastMatchResult ir_types_match_with_implicit_cast(IrAnalyze *ira,
         assert(ptr_type->id == TypeTableEntryIdPointer);
 
         if ((ptr_type->data.pointer.is_const || actual_type->data.array.len == 0) &&
-            types_match_const_cast_only(ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
+            types_match_const_cast_only(ira->codegen, ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
         {
             return ImplicitCastMatchResultYes;
         }
@@ -6482,7 +6475,7 @@ static ImplicitCastMatchResult ir_types_match_with_implicit_cast(IrAnalyze *ira,
         TypeTableEntry *array_type = actual_type->data.pointer.child_type;
 
         if ((ptr_type->data.pointer.is_const || array_type->data.array.len == 0) &&
-            types_match_const_cast_only(ptr_type->data.pointer.child_type, array_type->data.array.child_type))
+            types_match_const_cast_only(ira->codegen, ptr_type->data.pointer.child_type, array_type->data.array.child_type))
         {
             return ImplicitCastMatchResultYes;
         }
@@ -6498,7 +6491,7 @@ static ImplicitCastMatchResult ir_types_match_with_implicit_cast(IrAnalyze *ira,
             expected_type->data.pointer.child_type->data.structure.fields[slice_ptr_index].type_entry;
         assert(ptr_type->id == TypeTableEntryIdPointer);
         if ((ptr_type->data.pointer.is_const || actual_type->data.array.len == 0) &&
-                types_match_const_cast_only(ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
+                types_match_const_cast_only(ira->codegen, ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
         {
             return ImplicitCastMatchResultYes;
         }
@@ -6513,7 +6506,7 @@ static ImplicitCastMatchResult ir_types_match_with_implicit_cast(IrAnalyze *ira,
             expected_type->data.maybe.child_type->data.structure.fields[slice_ptr_index].type_entry;
         assert(ptr_type->id == TypeTableEntryIdPointer);
         if ((ptr_type->data.pointer.is_const || actual_type->data.array.len == 0) &&
-                types_match_const_cast_only(ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
+                types_match_const_cast_only(ira->codegen, ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
         {
             return ImplicitCastMatchResultYes;
         }
@@ -6593,7 +6586,7 @@ static ImplicitCastMatchResult ir_types_match_with_implicit_cast(IrAnalyze *ira,
     // implicitly take a const pointer to something
     if (!type_requires_comptime(actual_type)) {
         TypeTableEntry *const_ptr_actual = get_pointer_to_type(ira->codegen, actual_type, true);
-        if (types_match_const_cast_only(expected_type, const_ptr_actual)) {
+        if (types_match_const_cast_only(ira->codegen, expected_type, const_ptr_actual)) {
             return ImplicitCastMatchResultYes;
         }
     }
@@ -6769,11 +6762,11 @@ static TypeTableEntry *ir_resolve_peer_types(IrAnalyze *ira, AstNode *source_nod
             }
         }
 
-        if (types_match_const_cast_only(prev_type, cur_type)) {
+        if (types_match_const_cast_only(ira->codegen, prev_type, cur_type)) {
             continue;
         }
 
-        if (types_match_const_cast_only(cur_type, prev_type)) {
+        if (types_match_const_cast_only(ira->codegen, cur_type, prev_type)) {
             prev_inst = cur_inst;
             continue;
         }
@@ -6796,26 +6789,26 @@ static TypeTableEntry *ir_resolve_peer_types(IrAnalyze *ira, AstNode *source_nod
         }
 
         if (prev_type->id == TypeTableEntryIdErrorUnion &&
-                types_match_const_cast_only(prev_type->data.error_union.payload_type, cur_type))
+                types_match_const_cast_only(ira->codegen, prev_type->data.error_union.payload_type, cur_type))
         {
             continue;
         }
 
         if (cur_type->id == TypeTableEntryIdErrorUnion &&
-                types_match_const_cast_only(cur_type->data.error_union.payload_type, prev_type))
+                types_match_const_cast_only(ira->codegen, cur_type->data.error_union.payload_type, prev_type))
         {
             prev_inst = cur_inst;
             continue;
         }
 
         if (prev_type->id == TypeTableEntryIdMaybe &&
-            types_match_const_cast_only(prev_type->data.maybe.child_type, cur_type))
+            types_match_const_cast_only(ira->codegen, prev_type->data.maybe.child_type, cur_type))
         {
             continue;
         }
 
         if (cur_type->id == TypeTableEntryIdMaybe &&
-                   types_match_const_cast_only(cur_type->data.maybe.child_type, prev_type))
+                   types_match_const_cast_only(ira->codegen, cur_type->data.maybe.child_type, prev_type))
         {
             prev_inst = cur_inst;
             continue;
@@ -6853,7 +6846,7 @@ static TypeTableEntry *ir_resolve_peer_types(IrAnalyze *ira, AstNode *source_nod
 
         if (cur_type->id == TypeTableEntryIdArray && prev_type->id == TypeTableEntryIdArray &&
                 cur_type->data.array.len != prev_type->data.array.len &&
-                types_match_const_cast_only(cur_type->data.array.child_type, prev_type->data.array.child_type))
+                types_match_const_cast_only(ira->codegen, cur_type->data.array.child_type, prev_type->data.array.child_type))
         {
             convert_to_const_slice = true;
             prev_inst = cur_inst;
@@ -6862,7 +6855,7 @@ static TypeTableEntry *ir_resolve_peer_types(IrAnalyze *ira, AstNode *source_nod
 
         if (cur_type->id == TypeTableEntryIdArray && prev_type->id == TypeTableEntryIdArray &&
                 cur_type->data.array.len != prev_type->data.array.len &&
-                types_match_const_cast_only(prev_type->data.array.child_type, cur_type->data.array.child_type))
+                types_match_const_cast_only(ira->codegen, prev_type->data.array.child_type, cur_type->data.array.child_type))
         {
             convert_to_const_slice = true;
             continue;
@@ -6871,7 +6864,7 @@ static TypeTableEntry *ir_resolve_peer_types(IrAnalyze *ira, AstNode *source_nod
         if (cur_type->id == TypeTableEntryIdArray && is_slice(prev_type) &&
             (prev_type->data.structure.fields[slice_ptr_index].type_entry->data.pointer.is_const ||
             cur_type->data.array.len == 0) &&
-            types_match_const_cast_only(prev_type->data.structure.fields[slice_ptr_index].type_entry->data.pointer.child_type,
+            types_match_const_cast_only(ira->codegen, prev_type->data.structure.fields[slice_ptr_index].type_entry->data.pointer.child_type,
                 cur_type->data.array.child_type))
         {
             convert_to_const_slice = false;
@@ -6881,7 +6874,7 @@ static TypeTableEntry *ir_resolve_peer_types(IrAnalyze *ira, AstNode *source_nod
         if (prev_type->id == TypeTableEntryIdArray && is_slice(cur_type) &&
             (cur_type->data.structure.fields[slice_ptr_index].type_entry->data.pointer.is_const ||
             prev_type->data.array.len == 0) &&
-            types_match_const_cast_only(cur_type->data.structure.fields[slice_ptr_index].type_entry->data.pointer.child_type,
+            types_match_const_cast_only(ira->codegen, cur_type->data.structure.fields[slice_ptr_index].type_entry->data.pointer.child_type,
             prev_type->data.array.child_type))
         {
             prev_inst = cur_inst;
@@ -7449,6 +7442,7 @@ static IrInstruction *ir_analyze_err_wrap_payload(IrAnalyze *ira, IrInstruction
     return result;
 }
 
+// TODO this is an explicit cast and should actually coerce the type
 static IrInstruction *ir_analyze_err_set_cast(IrAnalyze *ira, IrInstruction *source_instr, IrInstruction *value,
         TypeTableEntry *wanted_type)
 {
@@ -7999,7 +7993,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
         return value;
 
     // explicit match or non-const to const
-    if (types_match_const_cast_only(wanted_type, actual_type)) {
+    if (types_match_const_cast_only(ira->codegen, wanted_type, actual_type)) {
         return ir_resolve_cast(ira, source_instr, value, wanted_type, CastOpNoop, false);
     }
 
@@ -8045,7 +8039,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
         TypeTableEntry *ptr_type = wanted_type->data.structure.fields[slice_ptr_index].type_entry;
         assert(ptr_type->id == TypeTableEntryIdPointer);
         if ((ptr_type->data.pointer.is_const || actual_type->data.array.len == 0) &&
-            types_match_const_cast_only(ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
+            types_match_const_cast_only(ira->codegen, ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
         {
             return ir_analyze_array_to_slice(ira, source_instr, value, wanted_type);
         }
@@ -8063,7 +8057,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
         TypeTableEntry *array_type = actual_type->data.pointer.child_type;
 
         if ((ptr_type->data.pointer.is_const || array_type->data.array.len == 0) &&
-            types_match_const_cast_only(ptr_type->data.pointer.child_type, array_type->data.array.child_type))
+            types_match_const_cast_only(ira->codegen, ptr_type->data.pointer.child_type, array_type->data.array.child_type))
         {
             return ir_analyze_array_to_slice(ira, source_instr, value, wanted_type);
         }
@@ -8079,7 +8073,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
             wanted_type->data.pointer.child_type->data.structure.fields[slice_ptr_index].type_entry;
         assert(ptr_type->id == TypeTableEntryIdPointer);
         if ((ptr_type->data.pointer.is_const || actual_type->data.array.len == 0) &&
-                types_match_const_cast_only(ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
+                types_match_const_cast_only(ira->codegen, ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
         {
             IrInstruction *cast1 = ir_analyze_cast(ira, source_instr, wanted_type->data.pointer.child_type, value);
             if (type_is_invalid(cast1->value.type))
@@ -8102,7 +8096,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
             wanted_type->data.maybe.child_type->data.structure.fields[slice_ptr_index].type_entry;
         assert(ptr_type->id == TypeTableEntryIdPointer);
         if ((ptr_type->data.pointer.is_const || actual_type->data.array.len == 0) &&
-                types_match_const_cast_only(ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
+                types_match_const_cast_only(ira->codegen, ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
         {
             IrInstruction *cast1 = ir_analyze_cast(ira, source_instr, wanted_type->data.maybe.child_type, value);
             if (type_is_invalid(cast1->value.type))
@@ -8164,7 +8158,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
 
     // explicit cast from child type of maybe type to maybe type
     if (wanted_type->id == TypeTableEntryIdMaybe) {
-        if (types_match_const_cast_only(wanted_type->data.maybe.child_type, actual_type)) {
+        if (types_match_const_cast_only(ira->codegen, wanted_type->data.maybe.child_type, actual_type)) {
             return ir_analyze_maybe_wrap(ira, source_instr, value, wanted_type);
         } else if (actual_type->id == TypeTableEntryIdNumLitInt ||
                    actual_type->id == TypeTableEntryIdNumLitFloat)
@@ -8186,7 +8180,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
 
     // explicit cast from child type of error type to error type
     if (wanted_type->id == TypeTableEntryIdErrorUnion) {
-        if (types_match_const_cast_only(wanted_type->data.error_union.payload_type, actual_type)) {
+        if (types_match_const_cast_only(ira->codegen, wanted_type->data.error_union.payload_type, actual_type)) {
             return ir_analyze_err_wrap_payload(ira, source_instr, value, wanted_type);
         } else if (actual_type->id == TypeTableEntryIdNumLitInt ||
                    actual_type->id == TypeTableEntryIdNumLitFloat)
@@ -8208,7 +8202,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
             wanted_type->data.error_union.payload_type->data.structure.fields[slice_ptr_index].type_entry;
         assert(ptr_type->id == TypeTableEntryIdPointer);
         if ((ptr_type->data.pointer.is_const || actual_type->data.array.len == 0) &&
-                types_match_const_cast_only(ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
+                types_match_const_cast_only(ira->codegen, ptr_type->data.pointer.child_type, actual_type->data.array.child_type))
         {
             IrInstruction *cast1 = ir_analyze_cast(ira, source_instr, wanted_type->data.error_union.payload_type, value);
             if (type_is_invalid(cast1->value.type))
@@ -8235,7 +8229,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
         actual_type->id != TypeTableEntryIdMaybe)
     {
         TypeTableEntry *wanted_child_type = wanted_type->data.error_union.payload_type->data.maybe.child_type;
-        if (types_match_const_cast_only(wanted_child_type, actual_type) ||
+        if (types_match_const_cast_only(ira->codegen, wanted_child_type, actual_type) ||
             actual_type->id == TypeTableEntryIdNullLit ||
             actual_type->id == TypeTableEntryIdNumLitInt ||
             actual_type->id == TypeTableEntryIdNumLitFloat)
@@ -8385,7 +8379,7 @@ static IrInstruction *ir_analyze_cast(IrAnalyze *ira, IrInstruction *source_inst
     // explicit cast from something to const pointer of it
     if (!type_requires_comptime(actual_type)) {
         TypeTableEntry *const_ptr_actual = get_pointer_to_type(ira->codegen, actual_type, true);
-        if (types_match_const_cast_only(wanted_type, const_ptr_actual)) {
+        if (types_match_const_cast_only(ira->codegen, wanted_type, const_ptr_actual)) {
             return ir_analyze_cast_ref(ira, source_instr, value, wanted_type);
         }
     }
@@ -10386,12 +10380,17 @@ static TypeTableEntry *ir_analyze_fn_call(IrAnalyze *ira, IrInstructionCall *cal
 
         {
             AstNode *return_type_node = fn_proto_node->data.fn_proto.return_type;
-            TypeTableEntry *return_type = analyze_type_expr(ira->codegen, impl_fn->child_scope, return_type_node);
-            if (type_is_invalid(return_type))
+            TypeTableEntry *specified_return_type = analyze_type_expr(ira->codegen, impl_fn->child_scope, return_type_node);
+            if (type_is_invalid(specified_return_type))
                 return ira->codegen->builtin_types.entry_invalid;
-            inst_fn_type_id.return_type = return_type;
+            if (fn_proto_node->data.fn_proto.auto_err_set) {
+                TypeTableEntry *inferred_err_set_type = get_auto_err_set_type(ira->codegen, impl_fn);
+                inst_fn_type_id.return_type = get_error_union_type(ira->codegen, inferred_err_set_type, specified_return_type);
+            } else {
+                inst_fn_type_id.return_type = specified_return_type;
+            }
 
-            if (type_requires_comptime(return_type)) {
+            if (type_requires_comptime(specified_return_type)) {
                 // Throw out our work and call the function as if it were comptime.
                 return ir_analyze_fn_call(ira, call_instruction, fn_entry, fn_type, fn_ref, first_arg_ptr, true, FnInlineAuto);
             }
std/fmt/index.zig
@@ -220,7 +220,7 @@ pub fn formatValue(value: var, context: var, comptime Errors: type, output: fn(@
                 return formatValue(err, context, Errors, output);
             }
         },
-        builtin.TypeId.Error => {
+        builtin.TypeId.ErrorSet => {
             try output(context, "error.");
             return output(context, @errorName(value));
         },
std/os/index.zig
@@ -1158,7 +1158,12 @@ pub fn posix_setregid(rgid: u32, egid: u32) !void {
     };
 }
 
-pub fn windowsGetStdHandle(handle_id: windows.DWORD) !windows.HANDLE {
+pub const WindowsGetStdHandleErrs = error {
+    NoStdHandles,
+    Unexpected,
+};
+
+pub fn windowsGetStdHandle(handle_id: windows.DWORD) WindowsGetStdHandleErrs!windows.HANDLE {
     if (windows.GetStdHandle(handle_id)) |handle| {
         if (handle == windows.INVALID_HANDLE_VALUE) {
             const err = windows.GetLastError();
std/io.zig
@@ -26,7 +26,9 @@ test "import io tests" {
     }
 }
 
-pub fn getStdErr() !File {
+const GetStdIoErrs = os.WindowsGetStdHandleErrs;
+
+pub fn getStdErr() GetStdIoErrs!File {
     const handle = if (is_windows)
         try os.windowsGetStdHandle(system.STD_ERROR_HANDLE)
     else if (is_posix)
@@ -36,7 +38,7 @@ pub fn getStdErr() !File {
     return File.openHandle(handle);
 }
 
-pub fn getStdOut() !File {
+pub fn getStdOut() GetStdIoErrs!File {
     const handle = if (is_windows)
         try os.windowsGetStdHandle(system.STD_OUTPUT_HANDLE)
     else if (is_posix)
@@ -46,7 +48,7 @@ pub fn getStdOut() !File {
     return File.openHandle(handle);
 }
 
-pub fn getStdIn() !File {
+pub fn getStdIn() GetStdIoErrs!File {
     const handle = if (is_windows)
         try os.windowsGetStdHandle(system.STD_INPUT_HANDLE)
     else if (is_posix)
std/mem.zig
@@ -40,7 +40,7 @@ pub const Allocator = struct {
     }
 
     fn alignedAlloc(self: &Allocator, comptime T: type, comptime alignment: u29,
-        n: usize) %[]align(alignment) T
+        n: usize) ![]align(alignment) T
     {
         const byte_count = try math.mul(usize, @sizeOf(T), n);
         const byte_slice = try self.allocFn(self, byte_count, alignment);
@@ -56,7 +56,7 @@ pub const Allocator = struct {
     }
 
     fn alignedRealloc(self: &Allocator, comptime T: type, comptime alignment: u29,
-        old_mem: []align(alignment) T, n: usize) %[]align(alignment) T
+        old_mem: []align(alignment) T, n: usize) ![]align(alignment) T
     {
         if (old_mem.len == 0) {
             return self.alloc(T, n);
TODO
@@ -2,4 +2,5 @@ sed -i 's/\(\bfn .*) \)%\(.*{\)$/\1!\2/g' $(find .. -name "*.zig")
 
 comptime assert(error{} ! i32 == i32);
 
-
+// TODO this is an explicit cast and should actually coerce the type
+   erorr set casting