Commit 233049503a
Changed files (13)
test
behavior
cases
stage2
src/AstGen.zig
@@ -4557,9 +4557,6 @@ fn unionDeclInner(
wip_members.appendToField(@enumToInt(tag_value));
}
}
- if (field_count == 0) {
- return astgen.failNode(node, "union declarations must have at least one tag", .{});
- }
if (!block_scope.isEmpty()) {
_ = try block_scope.addBreak(.break_inline, decl_inst, .void_value);
@@ -4715,12 +4712,6 @@ fn containerDecl(
.nonexhaustive_node = nonexhaustive_node,
};
};
- if (counts.total_fields == 0 and counts.nonexhaustive_node == 0) {
- // One can construct an enum with no tags, and it functions the same as `noreturn`. But
- // this is only useful for generic code; when explicitly using `enum {}` syntax, there
- // must be at least one tag.
- try astgen.appendErrorNode(node, "enum declarations must have at least one tag", .{});
- }
if (counts.nonexhaustive_node != 0 and container_decl.ast.arg == 0) {
try astgen.appendErrorNodeNotes(
node,
src/print_zir.zig
@@ -1443,7 +1443,7 @@ const Writer = struct {
try self.writeFlag(stream, "autoenum, ", small.auto_enum_tag);
if (decls_len == 0) {
- try stream.writeAll("{}, ");
+ try stream.writeAll("{}");
} else {
const prev_parent_decl_node = self.parent_decl_node;
if (src_node) |off| self.parent_decl_node = self.relativeToNodeIndex(off);
@@ -1454,15 +1454,20 @@ const Writer = struct {
extra_index = try self.writeDecls(stream, decls_len, extra_index);
self.indent -= 2;
try stream.writeByteNTimes(' ', self.indent);
- try stream.writeAll("}, ");
+ try stream.writeAll("}");
}
- assert(fields_len != 0);
-
if (tag_type_ref != .none) {
- try self.writeInstRef(stream, tag_type_ref);
try stream.writeAll(", ");
+ try self.writeInstRef(stream, tag_type_ref);
+ }
+
+ if (fields_len == 0) {
+ try stream.writeAll("})");
+ try self.writeSrcNode(stream, src_node);
+ return;
}
+ try stream.writeAll(", ");
const body = self.code.extra[extra_index..][0..body_len];
extra_index += body.len;
src/Sema.zig
@@ -8979,6 +8979,8 @@ fn zirSwitchBlock(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError
var seen_union_fields: []?Module.SwitchProngSrc = &.{};
defer gpa.free(seen_union_fields);
+ var empty_enum = false;
+
const operand_ty = sema.typeOf(operand);
var else_error_ty: ?Type = null;
@@ -9012,6 +9014,7 @@ fn zirSwitchBlock(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError
.Union => unreachable, // handled in zirSwitchCond
.Enum => {
var seen_fields = try gpa.alloc(?Module.SwitchProngSrc, operand_ty.enumFieldCount());
+ empty_enum = seen_fields.len == 0 and !operand_ty.isNonexhaustiveEnum();
defer if (!union_originally) gpa.free(seen_fields);
if (union_originally) seen_union_fields = seen_fields;
mem.set(?Module.SwitchProngSrc, seen_fields, null);
@@ -9607,6 +9610,9 @@ fn zirSwitchBlock(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError
}
if (scalar_cases_len + multi_cases_len == 0) {
+ if (empty_enum) {
+ return Air.Inst.Ref.void_value;
+ }
if (special_prong == .none) {
return sema.fail(block, src, "switch must handle all possibilities", .{});
}
@@ -16690,43 +16696,39 @@ fn zirReify(sema: *Sema, block: *Block, extended: Zir.Inst.Extended.InstData, in
// Fields
const fields_len = try sema.usizeCast(block, src, fields_val.sliceLen(mod));
- if (fields_len > 0) {
- try enum_obj.fields.ensureTotalCapacity(new_decl_arena_allocator, fields_len);
- try enum_obj.values.ensureTotalCapacityContext(new_decl_arena_allocator, fields_len, .{
- .ty = enum_obj.tag_ty,
- .mod = mod,
- });
-
- var i: usize = 0;
- while (i < fields_len) : (i += 1) {
- const elem_val = try fields_val.elemValue(sema.mod, sema.arena, i);
- const field_struct_val = elem_val.castTag(.aggregate).?.data;
- // TODO use reflection instead of magic numbers here
- // name: []const u8
- const name_val = field_struct_val[0];
- // value: comptime_int
- const value_val = field_struct_val[1];
-
- const field_name = try name_val.toAllocatedBytes(
- Type.initTag(.const_slice_u8),
- new_decl_arena_allocator,
- sema.mod,
- );
+ try enum_obj.fields.ensureTotalCapacity(new_decl_arena_allocator, fields_len);
+ try enum_obj.values.ensureTotalCapacityContext(new_decl_arena_allocator, fields_len, .{
+ .ty = enum_obj.tag_ty,
+ .mod = mod,
+ });
- const gop = enum_obj.fields.getOrPutAssumeCapacity(field_name);
- if (gop.found_existing) {
- // TODO: better source location
- return sema.fail(block, src, "duplicate enum tag {s}", .{field_name});
- }
+ var i: usize = 0;
+ while (i < fields_len) : (i += 1) {
+ const elem_val = try fields_val.elemValue(sema.mod, sema.arena, i);
+ const field_struct_val = elem_val.castTag(.aggregate).?.data;
+ // TODO use reflection instead of magic numbers here
+ // name: []const u8
+ const name_val = field_struct_val[0];
+ // value: comptime_int
+ const value_val = field_struct_val[1];
+
+ const field_name = try name_val.toAllocatedBytes(
+ Type.initTag(.const_slice_u8),
+ new_decl_arena_allocator,
+ sema.mod,
+ );
- const copied_tag_val = try value_val.copy(new_decl_arena_allocator);
- enum_obj.values.putAssumeCapacityNoClobberContext(copied_tag_val, {}, .{
- .ty = enum_obj.tag_ty,
- .mod = mod,
- });
+ const gop = enum_obj.fields.getOrPutAssumeCapacity(field_name);
+ if (gop.found_existing) {
+ // TODO: better source location
+ return sema.fail(block, src, "duplicate enum tag {s}", .{field_name});
}
- } else {
- return sema.fail(block, src, "enums must have at least one field", .{});
+
+ const copied_tag_val = try value_val.copy(new_decl_arena_allocator);
+ enum_obj.values.putAssumeCapacityNoClobberContext(copied_tag_val, {}, .{
+ .ty = enum_obj.tag_ty,
+ .mod = mod,
+ });
}
try new_decl.finalizeNewArena(&new_decl_arena);
@@ -16851,58 +16853,54 @@ fn zirReify(sema: *Sema, block: *Block, extended: Zir.Inst.Extended.InstData, in
}
// Fields
- if (fields_len > 0) {
- try union_obj.fields.ensureTotalCapacity(new_decl_arena_allocator, fields_len);
+ try union_obj.fields.ensureTotalCapacity(new_decl_arena_allocator, fields_len);
- var i: usize = 0;
- while (i < fields_len) : (i += 1) {
- const elem_val = try fields_val.elemValue(sema.mod, sema.arena, i);
- const field_struct_val = elem_val.castTag(.aggregate).?.data;
- // TODO use reflection instead of magic numbers here
- // name: []const u8
- const name_val = field_struct_val[0];
- // field_type: type,
- const field_type_val = field_struct_val[1];
- // alignment: comptime_int,
- const alignment_val = field_struct_val[2];
-
- const field_name = try name_val.toAllocatedBytes(
- Type.initTag(.const_slice_u8),
- new_decl_arena_allocator,
- sema.mod,
- );
+ var i: usize = 0;
+ while (i < fields_len) : (i += 1) {
+ const elem_val = try fields_val.elemValue(sema.mod, sema.arena, i);
+ const field_struct_val = elem_val.castTag(.aggregate).?.data;
+ // TODO use reflection instead of magic numbers here
+ // name: []const u8
+ const name_val = field_struct_val[0];
+ // field_type: type,
+ const field_type_val = field_struct_val[1];
+ // alignment: comptime_int,
+ const alignment_val = field_struct_val[2];
- if (enum_field_names) |set| {
- set.putAssumeCapacity(field_name, {});
- }
+ const field_name = try name_val.toAllocatedBytes(
+ Type.initTag(.const_slice_u8),
+ new_decl_arena_allocator,
+ sema.mod,
+ );
- if (tag_ty_field_names) |*names| {
- const enum_has_field = names.orderedRemove(field_name);
- if (!enum_has_field) {
- const msg = msg: {
- const msg = try sema.errMsg(block, src, "no field named '{s}' in enum '{}'", .{ field_name, union_obj.tag_ty.fmt(sema.mod) });
- errdefer msg.destroy(sema.gpa);
- try sema.addDeclaredHereNote(msg, union_obj.tag_ty);
- break :msg msg;
- };
- return sema.failWithOwnedErrorMsg(msg);
- }
- }
+ if (enum_field_names) |set| {
+ set.putAssumeCapacity(field_name, {});
+ }
- const gop = union_obj.fields.getOrPutAssumeCapacity(field_name);
- if (gop.found_existing) {
- // TODO: better source location
- return sema.fail(block, src, "duplicate union field {s}", .{field_name});
+ if (tag_ty_field_names) |*names| {
+ const enum_has_field = names.orderedRemove(field_name);
+ if (!enum_has_field) {
+ const msg = msg: {
+ const msg = try sema.errMsg(block, src, "no field named '{s}' in enum '{}'", .{ field_name, union_obj.tag_ty.fmt(sema.mod) });
+ errdefer msg.destroy(sema.gpa);
+ try sema.addDeclaredHereNote(msg, union_obj.tag_ty);
+ break :msg msg;
+ };
+ return sema.failWithOwnedErrorMsg(msg);
}
+ }
- var buffer: Value.ToTypeBuffer = undefined;
- gop.value_ptr.* = .{
- .ty = try field_type_val.toType(&buffer).copy(new_decl_arena_allocator),
- .abi_align = @intCast(u32, alignment_val.toUnsignedInt(target)),
- };
+ const gop = union_obj.fields.getOrPutAssumeCapacity(field_name);
+ if (gop.found_existing) {
+ // TODO: better source location
+ return sema.fail(block, src, "duplicate union field {s}", .{field_name});
}
- } else {
- return sema.fail(block, src, "unions must have at least one field", .{});
+
+ var buffer: Value.ToTypeBuffer = undefined;
+ gop.value_ptr.* = .{
+ .ty = try field_type_val.toType(&buffer).copy(new_decl_arena_allocator),
+ .abi_align = @intCast(u32, alignment_val.toUnsignedInt(target)),
+ };
}
if (tag_ty_field_names) |names| {
@@ -28146,10 +28144,6 @@ fn semaUnionFields(mod: *Module, union_obj: *Module.Union) CompileError!void {
extra_index = decls_it.extra_index;
const body = zir.extra[extra_index..][0..body_len];
- if (fields_len == 0) {
- assert(body.len == 0);
- return;
- }
extra_index += body.len;
const decl = mod.declPtr(decl_index);
@@ -28237,6 +28231,10 @@ fn semaUnionFields(mod: *Module, union_obj: *Module.Union) CompileError!void {
enum_field_names = &union_obj.tag_ty.castTag(.enum_simple).?.data.fields;
}
+ if (fields_len == 0) {
+ return;
+ }
+
const bits_per_field = 4;
const fields_per_u32 = 32 / bits_per_field;
const bit_bags_count = std.math.divCeil(usize, fields_len, fields_per_u32) catch unreachable;
@@ -28772,7 +28770,9 @@ pub fn typeHasOnePossibleValue(
const union_obj = resolved_ty.cast(Type.Payload.Union).?.data;
const tag_val = (try sema.typeHasOnePossibleValue(block, src, union_obj.tag_ty)) orelse
return null;
- const only_field = union_obj.fields.values()[0];
+ const fields = union_obj.fields.values();
+ if (fields.len == 0) return Value.initTag(.empty_struct_value);
+ const only_field = fields[0];
if (only_field.ty.eql(resolved_ty, sema.mod)) {
const msg = try Module.ErrorMsg.create(
sema.gpa,
src/type.zig
@@ -2488,7 +2488,7 @@ pub const Type = extern union {
},
.union_safety_tagged, .union_tagged => {
const union_obj = ty.cast(Payload.Union).?.data;
- if (try union_obj.tag_ty.hasRuntimeBitsAdvanced(ignore_comptime_only, sema_kit)) {
+ if (union_obj.fields.count() > 0 and try union_obj.tag_ty.hasRuntimeBitsAdvanced(ignore_comptime_only, sema_kit)) {
return true;
}
if (sema_kit) |sk| {
@@ -3113,6 +3113,9 @@ pub const Type = extern union {
.sema_kit => unreachable, // handled above
.lazy => |arena| return AbiAlignmentAdvanced{ .val = try Value.Tag.lazy_align.create(arena, ty) },
};
+ if (union_obj.fields.count() == 0) {
+ return AbiAlignmentAdvanced{ .scalar = @boolToInt(union_obj.layout == .Extern) };
+ }
var max_align: u32 = 0;
if (have_tag) max_align = union_obj.tag_ty.abiAlignment(target);
test/behavior/empty_union.zig
@@ -0,0 +1,54 @@
+const builtin = @import("builtin");
+const std = @import("std");
+const expect = std.testing.expect;
+
+test "switch on empty enum" {
+ if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
+ if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
+
+ const E = enum {};
+ var e: E = undefined;
+ switch (e) {}
+}
+
+test "switch on empty enum with a specified tag type" {
+ if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
+ if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
+
+ const E = enum(u8) {};
+ var e: E = undefined;
+ switch (e) {}
+}
+
+test "switch on empty auto numbered tagged union" {
+ if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
+ if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
+ if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
+
+ const U = union(enum(u8)) {};
+ var u: U = undefined;
+ switch (u) {}
+}
+
+test "switch on empty tagged union" {
+ if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
+ if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
+ if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
+
+ const E = enum {};
+ const U = union(E) {};
+ var u: U = undefined;
+ switch (u) {}
+}
+
+test "empty union" {
+ const U = union {};
+ try expect(@sizeOf(U) == 0);
+ try expect(@alignOf(U) == 0);
+}
+
+test "empty extern union" {
+ const U = extern union {};
+ try expect(@sizeOf(U) == 0);
+ try expect(@alignOf(U) == 1);
+}
test/cases/compile_errors/enum_with_0_fields.zig
@@ -1,7 +0,0 @@
-const Foo = enum {};
-
-// error
-// backend=stage2
-// target=native
-//
-// :1:13: error: enum declarations must have at least one tag
test/cases/compile_errors/reify_type_for_exhaustive_enum_with_zero_fields.zig
@@ -1,18 +0,0 @@
-const Tag = @Type(.{
- .Enum = .{
- .layout = .Auto,
- .tag_type = u1,
- .fields = &.{},
- .decls = &.{},
- .is_exhaustive = true,
- },
-});
-export fn entry() void {
- _ = @intToEnum(Tag, 0);
-}
-
-// error
-// backend=stage2
-// target=native
-//
-// :1:13: error: enums must have at least one field
test/cases/compile_errors/reify_type_for_union_with_zero_fields.zig
@@ -1,17 +0,0 @@
-const Untagged = @Type(.{
- .Union = .{
- .layout = .Auto,
- .tag_type = null,
- .fields = &.{},
- .decls = &.{},
- },
-});
-export fn entry() void {
- _ = Untagged{};
-}
-
-// error
-// backend=stage2
-// target=native
-//
-// :1:18: error: unions must have at least one field
test/cases/compile_errors/union_fields_with_value_assignments.zig
@@ -1,7 +0,0 @@
-const Foo = union {};
-
-// error
-// backend=stage2
-// target=native
-//
-// :1:13: error: union declarations must have at least one tag
test/cases/compile_errors/union_with_0_fields.zig
@@ -1,7 +0,0 @@
-const Foo = union {};
-
-// error
-// backend=stage2
-// target=native
-//
-// :1:13: error: union declarations must have at least one tag
test/cases/compile_errors/using_invalid_types_in_function_call_raises_an_error.zig
@@ -1,11 +0,0 @@
-const MenuEffect = enum {};
-fn func(effect: MenuEffect) void { _ = effect; }
-export fn entry() void {
- func(MenuEffect.ThisDoesNotExist);
-}
-
-// error
-// backend=stage2
-// target=native
-//
-// :1:20: error: enum declarations must have at least one tag
test/stage2/cbe.zig
@@ -704,15 +704,6 @@ pub fn addCases(ctx: *TestContext) !void {
":5:9: error: '_' is used to mark an enum as non-exhaustive and cannot be assigned a value",
});
- case.addError(
- \\const E1 = enum {};
- \\export fn foo() void {
- \\ _ = E1.a;
- \\}
- , &.{
- ":1:12: error: enum declarations must have at least one tag",
- });
-
case.addError(
\\const E1 = enum { a, b, _ };
\\export fn foo() void {
test/behavior.zig
@@ -167,6 +167,7 @@ test {
if (builtin.zig_backend != .stage1) {
_ = @import("behavior/decltest.zig");
_ = @import("behavior/packed_struct_explicit_backing_int.zig");
+ _ = @import("behavior/empty_union.zig");
}
if (builtin.os.tag != .wasi) {