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stage1: Implement non-exhaustive tagged unions #8163

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43 changes: 42 additions & 1 deletion src/stage1/analyze.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3189,9 +3189,35 @@ static Error resolve_union_zero_bits(CodeGen *g, ZigType *union_type) {
union_type->data.unionation.resolve_loop_flag_zero_bits = true;

uint32_t field_count;
bool container_non_exhaustive;
if (decl_node->type == NodeTypeContainerDecl) {
AstNode *last_field_node = decl_node->data.container_decl.fields.at(decl_node->data.container_decl.fields.length - 1);
if (buf_eql_str(last_field_node->data.struct_field.name, "_")) {
if (last_field_node->data.struct_field.value != nullptr) {
add_node_error(g, last_field_node, buf_sprintf("value assigned to '_' field of non-exhaustive union"));
union_type->data.unionation.resolve_status = ResolveStatusInvalid;
return ErrorSemanticAnalyzeFail;
}
if (decl_node->data.container_decl.init_arg_expr == nullptr) {
add_node_error(g, decl_node, buf_sprintf("non-exhaustive enum must specify size"));
union_type->data.unionation.resolve_status = ResolveStatusInvalid;
return ErrorSemanticAnalyzeFail;
}
bool is_auto_enum = decl_node->data.container_decl.auto_enum;
bool is_explicit_enum = decl_node->data.container_decl.init_arg_expr != nullptr;
if (!is_auto_enum && !is_explicit_enum) {
add_node_error(g, decl_node, buf_sprintf("untagged union cannot be non-exhaustive"));
union_type->data.unionation.resolve_status = ResolveStatusInvalid;
return ErrorSemanticAnalyzeFail;
}
container_non_exhaustive = true;
} else {
container_non_exhaustive = false;
}

assert(union_type->data.unionation.fields == nullptr);
field_count = (uint32_t)decl_node->data.container_decl.fields.length;
field_count = (uint32_t)decl_node->data.container_decl.fields.length
- container_non_exhaustive;
union_type->data.unionation.src_field_count = field_count;
union_type->data.unionation.fields = heap::c_allocator.allocate<TypeUnionField>(field_count);
union_type->data.unionation.fields_by_name.init(field_count);
Expand Down Expand Up @@ -3287,6 +3313,7 @@ static Error resolve_union_zero_bits(CodeGen *g, ZigType *union_type) {
tag_type->data.enumeration.fields_by_name.init(field_count);
tag_type->data.enumeration.decls_scope = create_decls_scope(
g, nullptr, nullptr, tag_type, get_scope_import(scope), &tag_type->name);
tag_type->data.enumeration.non_exhaustive = container_non_exhaustive;
} else if (enum_type_node != nullptr) {
tag_type = analyze_type_expr(g, scope, enum_type_node);
} else {
Expand All @@ -3311,6 +3338,20 @@ static Error resolve_union_zero_bits(CodeGen *g, ZigType *union_type) {
assert(g->errors.length != 0);
return err;
}
if (decl_node->type == NodeTypeContainerDecl) {
if (container_non_exhaustive && !tag_type->data.enumeration.non_exhaustive) {
add_node_error(g, enum_type_node != nullptr ? enum_type_node : decl_node,
buf_sprintf("enum tag of non-exhaustive union must be non-exhaustive"));
union_type->data.unionation.resolve_status = ResolveStatusInvalid;
return ErrorSemanticAnalyzeFail;
}
if (!container_non_exhaustive && tag_type->data.enumeration.non_exhaustive) {
add_node_error(g, decl_node,
buf_sprintf("union with non-exhaustive enum tag must be non-exhaustive"));
union_type->data.unionation.resolve_status = ResolveStatusInvalid;
return ErrorSemanticAnalyzeFail;
}
}
covered_enum_fields = heap::c_allocator.allocate<bool>(tag_type->data.enumeration.src_field_count);
}
union_type->data.unionation.tag_type = tag_type;
Expand Down
9 changes: 1 addition & 8 deletions src/stage1/ir.cpp
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Expand Up @@ -29709,10 +29709,6 @@ static IrInstGen *ir_analyze_instruction_check_switch_prongs(IrAnalyze *ira,
if (type_is_invalid(switch_type))
return ira->codegen->invalid_inst_gen;

ZigValue *original_value = ((IrInstSrcSwitchTarget *)(instruction->target_value))->target_value_ptr->child->value;
bool target_is_originally_union = original_value->type->id == ZigTypeIdPointer &&
original_value->type->data.pointer.child_type->id == ZigTypeIdUnion;

if (switch_type->id == ZigTypeIdEnum) {
HashMap<BigInt, AstNode *, bigint_hash, bigint_eql> field_prev_uses = {};
field_prev_uses.init(switch_type->data.enumeration.src_field_count);
Expand Down Expand Up @@ -29771,9 +29767,6 @@ static IrInstGen *ir_analyze_instruction_check_switch_prongs(IrAnalyze *ira,
if (!switch_type->data.enumeration.non_exhaustive) {
ir_add_error(ira, &instruction->base.base,
buf_sprintf("switch on exhaustive enum has `_` prong"));
} else if (target_is_originally_union) {
ir_add_error(ira, &instruction->base.base,
buf_sprintf("`_` prong not allowed when switching on tagged union"));
}
for (uint32_t i = 0; i < switch_type->data.enumeration.src_field_count; i += 1) {
TypeEnumField *enum_field = &switch_type->data.enumeration.fields[i];
Expand All @@ -29788,7 +29781,7 @@ static IrInstGen *ir_analyze_instruction_check_switch_prongs(IrAnalyze *ira,
}
}
} else if (instruction->else_prong == nullptr) {
if (switch_type->data.enumeration.non_exhaustive && !target_is_originally_union) {
if (switch_type->data.enumeration.non_exhaustive) {
ir_add_error(ira, &instruction->base.base,
buf_sprintf("switch on non-exhaustive enum must include `else` or `_` prong"));
}
Expand Down
60 changes: 60 additions & 0 deletions test/compile_errors.zig
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Expand Up @@ -2,6 +2,66 @@ const tests = @import("tests.zig");
const std = @import("std");

pub fn addCases(cases: *tests.CompileErrorContext) void {
cases.add("non-exhaustive switch on non-exhaustive unions",
\\const A = union((enum(u32) { a, b, _ })) { a: u32, b: u32, _ };
\\const B = union(enum(u32)) { a: u32, b: u32, _ };
\\fn check(x: anytype) void {
\\ switch (x) {
\\ .a => |n| {},
\\ .b => |n| {},
\\ }
\\ switch (x) {
\\ .a => |n| {},
\\ _ => {},
\\ }
\\ switch (x) {
\\ .a => |n| {},
\\ }
\\}
\\export fn foo() void {
\\ var x = A{ .a = 0 };
\\ var y = B{ .a = 0 };
\\ check(x);
\\ check(y);
\\}
, &[_][]const u8{
"tmp.zig:4:5: error: switch on non-exhaustive enum must include `else` or `_` prong",
"tmp.zig:8:5: error: enumeration value 'enum:1:18.b' not handled in switch",
"tmp.zig:12:5: error: switch on non-exhaustive enum must include `else` or `_` prong",
"tmp.zig:12:5: error: enumeration value 'enum:1:18.b' not handled in switch",
"tmp.zig:4:5: error: switch on non-exhaustive enum must include `else` or `_` prong",
"tmp.zig:8:5: error: enumeration value '@typeInfo(B).Union.tag_type.?.b' not handled in switch",
"tmp.zig:12:5: error: switch on non-exhaustive enum must include `else` or `_` prong",
"tmp.zig:12:5: error: enumeration value '@typeInfo(B).Union.tag_type.?.b' not handled in switch",
});

cases.add("exhaustive enum tag on non-exhaustive union",
\\const C = union((enum(u32) { a, b })) { a: u32, b: u32, _ };
\\export fn foo() void {
\\ _ = C{ .a = 0 };
\\}
, &[_][]const u8{
"tmp.zig:1:17: error: enum tag of non-exhaustive union must be non-exhaustive",
});

cases.add("non-exhautive enum tag on exhaustive union",
\\const D = union((enum(u32) { a, b, _ })) { a: u32, b: u32 };
\\export fn foo() void {
\\ _ = D{ .a = 0 };
\\}
, &[_][]const u8{
"tmp.zig:1:11: error: union with non-exhaustive enum tag must be non-exhaustive",
});

cases.add("non-exhaustive union without explicit enum size",
\\const E = union(enum) { a: u32, b: u32, _ };
\\export fn foo() void {
\\ _ = E{ .a = 0 };
\\}
, &[_][]const u8{
"tmp.zig:1:11: error: non-exhaustive enum must specify size",
});

cases.add("lazy pointer with undefined element type",
\\export fn foo() void {
\\ comptime var T: type = undefined;
Expand Down
25 changes: 25 additions & 0 deletions test/stage1/behavior/union.zig
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Expand Up @@ -726,12 +726,14 @@ test "switching on non exhaustive union" {
const U = union(E) {
a: i32,
b: u32,
_,
};
fn doTheTest() void {
var a = U{ .a = 2 };
switch (a) {
.a => |val| expect(val == 2),
.b => unreachable,
_ => unreachable,
}
}
};
Expand Down Expand Up @@ -804,3 +806,26 @@ test "union enum type gets a separate scope" {

S.doTheTest();
}

fn testNonExhaustive(x: anytype) void {
switch (x) {
.a => |n| {},
.b => |n| {},
_ => {},
}
switch (x) {
.a => |n| {},
else => {},
}
switch (x) {
.a => |n| {},
else => {},
}
}

test "non-exhaustive unions" {
const A = union((enum(u32) { a, b, _ })) { a: u32, b: u32, _ };
const B = union(enum(u32)) { a: u32, b: u32, _ };
testNonExhaustive(A{ .a = 0 });
testNonExhaustive(B{ .a = 0 });
}