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AstGen: allow breaking from labeled switch
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Also, don't use the special switch lowering for errors if the switch
is labeled; this isn't currently supported. Related: ziglang#20627.
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@mlugg
mlugg committed Aug 30, 2024
1 parent 4cc084f commit 6ab4c41
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Showing 2 changed files with 38 additions and 21 deletions.
35 changes: 14 additions & 21 deletions lib/std/zig/AstGen.zig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -857,13 +857,10 @@ fn expr(gz: *GenZir, scope: *Scope, ri: ResultInfo, node: Ast.Node.Index) InnerE
const if_full = tree.fullIf(node).?;
no_switch_on_err: {
const error_token = if_full.error_token orelse break :no_switch_on_err;
switch (node_tags[if_full.ast.else_expr]) {
.@"switch", .switch_comma => {},
else => break :no_switch_on_err,
}
const switch_operand = node_datas[if_full.ast.else_expr].lhs;
if (node_tags[switch_operand] != .identifier) break :no_switch_on_err;
if (!mem.eql(u8, tree.tokenSlice(error_token), tree.tokenSlice(main_tokens[switch_operand]))) break :no_switch_on_err;
const full_switch = tree.fullSwitch(node_datas[node].rhs) orelse break :no_switch_on_err;
if (full_switch.label_token != null) break :no_switch_on_err;
if (node_tags[full_switch.ast.condition] != .identifier) break :no_switch_on_err;
if (!mem.eql(u8, tree.tokenSlice(error_token), tree.tokenSlice(main_tokens[full_switch.ast.condition]))) break :no_switch_on_err;
return switchExprErrUnion(gz, scope, ri.br(), node, .@"if");
}
return ifExpr(gz, scope, ri.br(), node, if_full);
Expand Down Expand Up @@ -1049,13 +1046,10 @@ fn expr(gz: *GenZir, scope: *Scope, ri: ResultInfo, node: Ast.Node.Index) InnerE
null;
no_switch_on_err: {
const capture_token = payload_token orelse break :no_switch_on_err;
switch (node_tags[node_datas[node].rhs]) {
.@"switch", .switch_comma => {},
else => break :no_switch_on_err,
}
const switch_operand = node_datas[node_datas[node].rhs].lhs;
if (node_tags[switch_operand] != .identifier) break :no_switch_on_err;
if (!mem.eql(u8, tree.tokenSlice(capture_token), tree.tokenSlice(main_tokens[switch_operand]))) break :no_switch_on_err;
const full_switch = tree.fullSwitch(node_datas[node].rhs) orelse break :no_switch_on_err;
if (full_switch.label_token != null) break :no_switch_on_err;
if (node_tags[full_switch.ast.condition] != .identifier) break :no_switch_on_err;
if (!mem.eql(u8, tree.tokenSlice(capture_token), tree.tokenSlice(main_tokens[full_switch.ast.condition]))) break :no_switch_on_err;
return switchExprErrUnion(gz, scope, ri.br(), node, .@"catch");
}
switch (ri.rl) {
Expand Down Expand Up @@ -2160,11 +2154,6 @@ fn breakExpr(parent_gz: *GenZir, parent_scope: *Scope, node: Ast.Node.Index) Inn
if (break_label != 0) {
if (block_gz.label) |*label| {
if (try astgen.tokenIdentEql(label.token, break_label)) {
const maybe_switch_tag = astgen.instructions.items(.tag)[@intFromEnum(label.block_inst)];
switch (maybe_switch_tag) {
.switch_block, .switch_block_ref => return astgen.failNode(node, "cannot break from switch", .{}),
else => {},
}
label.used = true;
break :blk label.block_inst;
}
Expand Down Expand Up @@ -2278,6 +2267,7 @@ fn continueExpr(parent_gz: *GenZir, parent_scope: *Scope, node: Ast.Node.Index)
}

label.used = true;
label.used_for_continue = true;
break :blk;
}
}
Expand Down Expand Up @@ -7760,7 +7750,7 @@ fn switchExpr(
const raw_operand = try expr(parent_gz, scope, operand_ri, operand_node);
const item_ri: ResultInfo = .{ .rl = .none };

// If this switch is labeled, it will have `continue`s targeting it, and thus we need the operand type
// If this switch is labeled, it may have `continue`s targeting it, and thus we need the operand type
// to provide a result type.
const raw_operand_ty_ref = if (switch_full.label_token != null) t: {
break :t try parent_gz.addUnNode(.typeof, raw_operand, operand_node);
Expand Down Expand Up @@ -7790,7 +7780,9 @@ fn switchExpr(
const switch_block = try parent_gz.makeBlockInst(switch_tag, node);

if (switch_full.label_token) |label_token| {
block_scope.break_block = switch_block.toOptional();
block_scope.continue_block = switch_block.toOptional();
// `break_result_info` already set above
block_scope.continue_result_info = .{
.rl = if (any_payload_is_ref)
.{ .ref_coerced_ty = raw_operand_ty_ref }
Expand Down Expand Up @@ -8024,7 +8016,7 @@ fn switchExpr(
.has_under = special_prong == .under,
.any_has_tag_capture = any_has_tag_capture,
.any_non_inline_capture = any_non_inline_capture,
.has_continue = switch_full.label_token != null,
.has_continue = switch_full.label_token != null and block_scope.label.?.used_for_continue,
.scalar_cases_len = @intCast(scalar_cases_len),
},
});
Expand Down Expand Up @@ -11963,6 +11955,7 @@ const GenZir = struct {
token: Ast.TokenIndex,
block_inst: Zir.Inst.Index,
used: bool = false,
used_for_continue: bool = false,
};

/// Assumes nothing stacked on `gz`.
Expand Down
24 changes: 24 additions & 0 deletions test/behavior/switch.zig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -961,3 +961,27 @@ test "block error return trace index is reset between prongs" {
};
try result;
}

test "labeled switch with break" {
var six: u32 = undefined;
six = 6;

const val = s: switch (six) {
0...4 => break :s false,
5 => break :s false,
6...7 => break :s true,
else => break :s false,
};

try expect(val);

// Make sure the switch is implicitly comptime!
const comptime_val = s: switch(@as(u32, 6)) {
0...4 => break :s false,
5 => break :s false,
6...7 => break :s true,
else => break :s false,
};

comptime assert(comptime_val);
}

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