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stage2: able to slice to sentinel index at comptime

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The runtime behavior allowed this in both stage1 and stage2, but stage1
fails with index out of bounds during comptime. This behavior makes
sense to support, and comptime behavior should match runtime behavior. I
implement this fix only in stage2.
This commit is contained in:
Mitchell Hashimoto 2022-03-23 09:40:29 -07:00 • committed by Andrew Kelley
parent f27d3409bd
commit a36f4ee290
3 changed files with 87 additions and 9 deletions
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39
src/Sema.zig
View file

@ -19713,17 +19713,31 @@ fn analyzeSlice(
if (!end_is_len) {
const end = try sema.coerce(block, Type.usize, uncasted_end_opt, end_src);
if (try sema.resolveMaybeUndefVal(block, end_src, end)) |end_val| {
if (end_val.compare(.gt, len_val, Type.usize, target)) {
const len_s_val = try Value.Tag.int_u64.create(
sema.arena,
array_ty.arrayLenIncludingSentinel(),
);
if (end_val.compare(.gt, len_s_val, Type.usize, target)) {
const sentinel_label: []const u8 = if (array_ty.sentinel() != null)
" +1 (sentinel)"
else
"";
return sema.fail(
block,
end_src,
"end index {} out of bounds for array of length {}",
"end index {} out of bounds for array of length {}{s}",
.{
end_val.fmtValue(Type.usize, target),
len_val.fmtValue(Type.usize, target),
sentinel_label,
},
);
}
// end_is_len is only true if we are NOT using the sentinel
// length. For sentinel-length, we don't want the type to
// contain the sentinel.
if (end_val.eql(len_val, Type.usize, target)) {
end_is_len = true;
}
@ -19737,22 +19751,37 @@ fn analyzeSlice(
const end = try sema.coerce(block, Type.usize, uncasted_end_opt, end_src);
if (try sema.resolveDefinedValue(block, end_src, end)) |end_val| {
if (try sema.resolveDefinedValue(block, src, ptr_or_slice)) |slice_val| {
const has_sentinel = slice_ty.sentinel() != null;
var int_payload: Value.Payload.U64 = .{
.base = .{ .tag = .int_u64 },
.data = slice_val.sliceLen(target),
.data = slice_val.sliceLen(target) + @boolToInt(has_sentinel),
};
const slice_len_val = Value.initPayload(&int_payload.base);
if (end_val.compare(.gt, slice_len_val, Type.usize, target)) {
const sentinel_label: []const u8 = if (has_sentinel)
" +1 (sentinel)"
else
"";
return sema.fail(
block,
end_src,
"end index {} out of bounds for slice of length {}",
"end index {} out of bounds for slice of length {d}{s}",
.{
end_val.fmtValue(Type.usize, target),
slice_len_val.fmtValue(Type.usize, target),
slice_val.sliceLen(target),
sentinel_label,
},
);
}
// If the slice has a sentinel, we subtract one so that
// end_is_len is only true if it equals the length WITHOUT
// the sentinel, so we don't add a sentinel type.
if (has_sentinel) {
int_payload.data -= 1;
}
if (end_val.eql(slice_len_val, Type.usize, target)) {
end_is_len = true;
}

43
test/behavior/slice.zig
View file

@ -640,3 +640,46 @@ test "slice sentinel access at comptime" {
try expect(slice0[slice0.len] == 0);
}
}
test "slicing array with sentinel as end index" {
// Doesn't work in stage1
if (builtin.zig_backend == .stage1) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
const S = struct {
fn do() !void {
var array = [_:0]u8{ 1, 2, 3, 4 };
var slice = array[4..5];
try expect(slice.len == 1);
try expect(slice[0] == 0);
try expect(@TypeOf(slice) == *[1]u8);
}
};
try S.do();
comptime try S.do();
}
test "slicing slice with sentinel as end index" {
// Doesn't work in stage1
if (builtin.zig_backend == .stage1) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
const S = struct {
fn do() !void {
var array = [_:0]u8{ 1, 2, 3, 4 };
var src_slice: [:0]u8 = &array;
var slice = src_slice[4..5];
try expect(slice.len == 1);
try expect(slice[0] == 0);
try expect(@TypeOf(slice) == *[1]u8);
}
};
try S.do();
comptime try S.do();
}

14
test/compile_errors.zig
View file

@ -26,11 +26,16 @@ pub fn addCases(ctx: *TestContext) !void {
\\comptime {
\\ var array = [_:0]u8{ 1, 2, 3, 4 };
\\ var src_slice: [:0]u8 = &array;
\\ var slice = src_slice[2..5];
\\ var slice = src_slice[2..6];
\\ _ = slice;
\\}
\\comptime {
\\ var array = [_:0]u8{ 1, 2, 3, 4 };
\\ var slice = array[2..6];
\\ _ = slice;
\\}
\\comptime {
\\ var array = [_]u8{ 1, 2, 3, 4 };
\\ var slice = array[2..5];
\\ _ = slice;
\\}
@ -40,9 +45,10 @@ pub fn addCases(ctx: *TestContext) !void {
\\ _ = slice;
\\}
, &[_][]const u8{
":4:26: error: end index 5 out of bounds for slice of length 4",
":9:22: error: end index 5 out of bounds for array of length 4",
":14:22: error: start index 3 is larger than end index 2",
":4:26: error: end index 6 out of bounds for slice of length 4 +1 (sentinel)",
":9:22: error: end index 6 out of bounds for array of length 4 +1 (sentinel)",
":14:22: error: end index 5 out of bounds for array of length 4",
":19:22: error: start index 3 is larger than end index 2",
});
}