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std.enums: fix EnumIndexer branch quota

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It's quite silly to have this override which nonetheless makes
assumptions about the input type. Encode the actual complexity of the
sort.

Also, simplify the sorting logic, and fix a bug (grab min and max
*after* the sort, not *before*!)
This commit is contained in:
mlugg 2025-07-31 10:10:40 +01:00 • committed by Matthew Lugg
parent 04d7b491b4
commit ac1e73e249
1 changed files with 36 additions and 22 deletions
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58
lib/std/enums.zig
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@ -1317,9 +1317,9 @@ test "EnumSet non-exhaustive" {
}
pub fn EnumIndexer(comptime E: type) type {
// Assumes that the enum fields are sorted in ascending order (optimistic).
// Unsorted enums may require the user to manually increase the quota.
@setEvalBranchQuota(3 * @typeInfo(E).@"enum".fields.len + eval_branch_quota_cushion);
// n log n for `std.mem.sortUnstable` call below.
const fields_len = @typeInfo(E).@"enum".fields.len;
@setEvalBranchQuota(3 * fields_len * std.math.log2(@max(fields_len, 1)) + eval_branch_quota_cushion);
if (!@typeInfo(E).@"enum".is_exhaustive) {
const BackingInt = @typeInfo(E).@"enum".tag_type;
@ -1354,10 +1354,6 @@ pub fn EnumIndexer(comptime E: type) type {
};
}
const const_fields = @typeInfo(E).@"enum".fields;
var fields = const_fields[0..const_fields.len].*;
const fields_len = fields.len;
if (fields_len == 0) {
return struct {
pub const Key = E;
@ -1373,22 +1369,17 @@ pub fn EnumIndexer(comptime E: type) type {
};
}
var fields: [fields_len]EnumField = @typeInfo(E).@"enum".fields[0..].*;
std.mem.sortUnstable(EnumField, &fields, {}, struct {
fn lessThan(ctx: void, lhs: EnumField, rhs: EnumField) bool {
ctx;
return lhs.value < rhs.value;
}
}.lessThan);
const min = fields[0].value;
const max = fields[fields.len - 1].value;
const SortContext = struct {
fields: []EnumField,
pub fn lessThan(comptime ctx: @This(), comptime a: usize, comptime b: usize) bool {
return ctx.fields[a].value < ctx.fields[b].value;
}
pub fn swap(comptime ctx: @This(), comptime a: usize, comptime b: usize) void {
return std.mem.swap(EnumField, &ctx.fields[a], &ctx.fields[b]);
}
};
std.sort.insertionContext(0, fields_len, SortContext{ .fields = &fields });
const max = fields[fields_len - 1].value;
if (max - min == fields.len - 1) {
return struct {
pub const Key = E;
@ -1538,6 +1529,29 @@ test "EnumIndexer empty" {
try testing.expectEqual(0, Indexer.count);
}
test "EnumIndexer large dense unsorted" {
@setEvalBranchQuota(500_000); // many `comptimePrint`s
// Make an enum with 500 fields with values in *descending* order.
const E = @Type(.{ .@"enum" = .{
.tag_type = u32,
.fields = comptime fields: {
var fields: [500]EnumField = undefined;
for (&fields, 0..) |*f, i| f.* = .{
.name = std.fmt.comptimePrint("f{d}", .{i}),
.value = 500 - i,
};
break :fields &fields;
},
.decls = &.{},
.is_exhaustive = true,
} });
const Indexer = EnumIndexer(E);
try testing.expectEqual(E.f0, Indexer.keyForIndex(499));
try testing.expectEqual(E.f499, Indexer.keyForIndex(0));
try testing.expectEqual(499, Indexer.indexOf(.f0));
try testing.expectEqual(0, Indexer.indexOf(.f499));
}
test values {
const E = enum {
X,