| author |  Justus Klausecker <justus@klausecker.de> 2026-07-24 16:50:07+02:00 |
| committer | Justus Klausecker <justus@klausecker.de> 2026-07-24 17:48:10+02:00 |
| log | d3056114f6f17bb4723cccfa4dd578ddafb909a9 |
| tree | 7a4d656adc0a413b83dca60b5e94fcee19c41eaf |
| parent | 619e54c81382d849f0bfcbe7e5c38f9b34390639 |
Sema: disallow unreachable `else` prong for tagged unions with nonexhaustive tag types
2 files changed, 57 insertions(+), 1 deletions(-)
src- test
- cases
- compile_errors
src/Sema.zig+1-1
| ... | @@ -11375,7 +11375,7 @@ fn validateSwitchBlock( | ... | @@ -11375,7 +11375,7 @@ fn validateSwitchBlock( |
| 11375 | 11375 | ||
| 11376 | if (has_else) { | 11376 | if (has_else) { |
| 11377 | if (all_tags_handled) { | 11377 | if (all_tags_handled) { |
| 11378 | if (item_ty.isNonexhaustiveEnum(zcu)) { | 11378 | if (operand_ty.isNonexhaustiveEnum(zcu)) { |
| 11379 | if (has_under) return sema.fail( | 11379 | if (has_under) return sema.fail( |
| 11380 | block, | 11380 | block, |
| 11381 | else_prong_src, | 11381 | else_prong_src, |
test/cases/compile_errors/switch_on_union_with_nonexhaustive_tag_is_exhaustive.zig created+56
| ... | @@ -0,0 +1,56 @@ | ||
| 1 | const E = enum(u8) { | ||
| 2 | a, | ||
| 3 | b, | ||
| 4 | _, | ||
| 5 | }; | ||
| 6 | const U = union(E) { | ||
| 7 | a, | ||
| 8 | b, | ||
| 9 | }; | ||
| 10 | fn foo() U { | ||
| 11 | return undefined; | ||
| 12 | } | ||
| 13 | |||
| 14 | export fn entry1() void { | ||
| 15 | const u = foo(); | ||
| 16 | switch (u) { | ||
| 17 | .a => {}, | ||
| 18 | } | ||
| 19 | } | ||
| 20 | export fn entry2() void { | ||
| 21 | const u = foo(); | ||
| 22 | switch (u) { | ||
| 23 | .a => {}, | ||
| 24 | .b => {}, | ||
| 25 | else => {}, | ||
| 26 | } | ||
| 27 | } | ||
| 28 | export fn entry3() void { | ||
| 29 | const u = foo(); | ||
| 30 | switch (u) { | ||
| 31 | .a => {}, | ||
| 32 | .b => {}, | ||
| 33 | _ => {}, | ||
| 34 | } | ||
| 35 | } | ||
| 36 | export fn entry4() void { | ||
| 37 | const u = foo(); | ||
| 38 | switch (u) { | ||
| 39 | .a => {}, | ||
| 40 | else => {}, | ||
| 41 | _ => {}, | ||
| 42 | } | ||
| 43 | } | ||
| 44 | |||
| 45 | // error | ||
| 46 | // | ||
| 47 | // :16:5: error: switch must handle all possibilities | ||
| 48 | // :3:5: note: unhandled enumeration value: 'b' | ||
| 49 | // :1:11: note: enum 'tmp.E' declared here | ||
| 50 | // :25:14: error: unreachable else prong; all cases already handled | ||
| 51 | // :30:5: error: '_' prong only allowed when switching on non-exhaustive enums | ||
| 52 | // :33:9: note: '_' prong here | ||
| 53 | // :30:5: note: consider using 'else' | ||
| 54 | // :38:5: error: '_' prong only allowed when switching on non-exhaustive enums | ||
| 55 | // :41:9: note: '_' prong here | ||
| 56 | // :38:5: note: consider using 'else' | ||