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Sema: fix single-range switch prong capture

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This kind of capture cannot always be comptime-known, assuming so caused
access of undefined memory during payload capture analysis!
This commit is contained in:
Justus Klausecker 2026-01-11 20:02:27 +01:00
parent 76dd39d531
commit e2338edb47
2 changed files with 32 additions and 20 deletions
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37
src/Sema.zig
View file

@ -10970,8 +10970,7 @@ fn analyzeSwitchBlock(
.case_idx = index,
} }),
capture == .by_ref,
is_special,
if (!is_special) case_vals else undefined,
if (is_special) .special else .{ .item_refs = &.{.fromValue(item_opv)} },
if (is_inline) .fromValue(item_opv) else .none,
validated_switch.else_err_ty,
);
@ -12569,11 +12568,7 @@ fn resolveSwitchProng(
operand_src,
capture_src,
capture == .by_ref,
kind == .special,
switch (kind) {
.item_refs => |item_refs| item_refs,
.has_ranges, .special => undefined,
},
kind,
inline_case_capture,
else_err_ty,
);
@ -12702,11 +12697,7 @@ fn analyzeSwitchProng(
operand_src,
capture_src,
capture == .by_ref,
kind == .special,
switch (kind) {
.item_refs => |item_refs| item_refs,
.has_ranges, .special => undefined,
},
kind,
inline_case_capture,
else_err_ty,
);
@ -12783,9 +12774,7 @@ fn analyzeSwitchPayloadCapture(
operand_src: LazySrcLoc,
capture_src: LazySrcLoc,
capture_by_ref: bool,
is_special_prong: bool,
/// May be `undefined` if `is_special_prong` is `true`.
case_vals: []const Air.Inst.Ref,
kind: SwitchProngKind,
/// If this is not `.none`, this is an inline capture.
inline_case_capture: Air.Inst.Ref,
else_err_ty: ?Type,
@ -12829,7 +12818,7 @@ fn analyzeSwitchPayloadCapture(
const operand_ptr_ty = if (capture_by_ref) sema.typeOf(operand_ptr) else undefined;
if (is_special_prong) {
if (kind == .special) {
if (capture_by_ref) return operand_ptr;
return switch (operand_ty.zigTypeTag(zcu)) {
.error_set => e: {
@ -12846,6 +12835,8 @@ fn analyzeSwitchPayloadCapture(
switch (operand_ty.zigTypeTag(zcu)) {
.@"union" => {
const case_vals = kind.item_refs;
const union_obj = zcu.typeToUnion(operand_ty).?;
const first_item_val = sema.resolveConstDefinedValue(case_block, .unneeded, case_vals[0], undefined) catch unreachable;
@ -13141,6 +13132,7 @@ fn analyzeSwitchPayloadCapture(
);
}
const case_vals = kind.item_refs;
if (case_vals.len == 1) {
const item_val = sema.resolveConstDefinedValue(case_block, .unneeded, case_vals[0], undefined) catch unreachable;
const item_ty = try pt.singleErrorSetType(item_val.getErrorName(zcu).unwrap().?);
@ -13161,11 +13153,16 @@ fn analyzeSwitchPayloadCapture(
// switch condition. It is comptime-known if there is only one item.
if (capture_by_ref) {
return operand_ptr;
} else if (case_vals.len == 1) {
return case_vals[0];
} else {
return operand_val;
}
switch (kind) {
.special => unreachable,
.item_refs => |case_vals| {
// If there's only a single item, the capture is comptime-known!
if (case_vals.len == 1) return case_vals[0];
},
.has_ranges => {},
}
return operand_val;
},
}
}

15
test/behavior/switch.zig
View file

@ -1307,3 +1307,18 @@ test "single-item prong in switch on enum has comptime-known capture" {
try E.doTheTest(.a);
try comptime E.doTheTest(.a);
}
test "single-range switch prong capture" {
const S = struct {
fn doTheTest(x: u8) !void {
switch (x) {
1...5 => |val| {
try expect(val == 2);
},
else => return error.TestFailed,
}
}
};
try S.doTheTest(2);
try comptime S.doTheTest(2);
}