82366a93df
A `-> (Enum, !E)` `return .variant` lowered the enum literal with
`target_type` set to the full failable tuple `(Enum, !E)` instead of the
success value type. The bare literal resolves its tag against `target_type`;
against a tuple it matched no variant (silent tag 0) and was stamped with the
tuple type, so `lowerFailableSuccessReturn` saw `val_ty == ret_ty` and took the
forwarding branch — returning the half-built `{value, undef}` aggregate and
never appending the `0` error slot. Every runtime read of the slot on the
success path (`cast(s64) e`, bare `if e`, `e == error.X`) saw garbage nonzero;
only the compile-time `if !e` proof masked it. The s32 case was already correct
because integer literals don't resolve variants against `target_type`.
Fix: in lowerReturn, narrow `target_type` to `failableSuccessType(ret_ty)` for
a value-carrying failable before lowering the returned expression. The enum
literal then resolves to its real ordinal and is typed as the value type, so
the success path correctly appends `0`. Forwarding (`return call()` / explicit
`(v, e)`) is unaffected — those still yield a value typed equal to the tuple.
Regression: examples/1055-errors-enum-value-failable-error-slot.sx reads the
error slot at runtime on the success path (cast, bare if, == error.X), checks a
non-zero ordinal (.blue=2, also corrupted to 0 pre-fix), and asserts the error
path still carries the right tag + error_tag_name. Fails pre-fix, passes after.
45 lines
2.0 KiB
Plaintext
45 lines
2.0 KiB
Plaintext
// Enum-valued value-carrying failable: the SUCCESS path must zero the trailing
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// error slot. Regression (issue 0097). A `-> (Enum, !E)` `return .variant`
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// resolves the enum literal against the function's VALUE type (the enum), not
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// the failable tuple — otherwise the literal mis-resolves (tag 0) and is stamped
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// with the tuple type, which the success-return lowering mistakes for a forwarded
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// full tuple and leaves the error slot UNDEFINED (read back as garbage nonzero).
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//
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// This pins the slot at RUNTIME on the success path (cast(s64) e, bare `if e`,
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// and `e == error.X`) — not only via the `if !e` proof that the compiler can
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// fold away. It also exercises a non-zero ordinal (`.blue` = 2) so a value slot
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// that collapses to 0 is caught, and asserts the error PATH still carries the
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// right tag and `error_tag_name`.
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#import "modules/std.sx";
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Color :: enum { red; green; blue; }
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E :: error { Nope }
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pick :: (s: string) -> (Color, !E) {
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if s == "red" { return .red; }
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if s == "blue" { return .blue; } // non-zero ordinal (2)
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raise error.Nope;
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}
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main :: () -> s32 {
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// ── success path: error slot MUST read 0 at runtime ──
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c, e := pick("red");
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print("success err int = {}\n", cast(s64) e); // 0
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if e { print("bare-if e: ERROR (WRONG)\n"); } else { print("bare-if e: ok\n"); }
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if e == error.Nope { print("e == Nope (WRONG)\n"); } else { print("e != Nope (ok)\n"); }
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if !e { print("guard !e: c = {}\n", cast(s64) c); } // 0 (red)
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// ── non-zero ordinal: value slot must carry the real ordinal ──
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c2, e2 := pick("blue");
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if !e2 { print("blue: err int = {}, c = {}\n", cast(s64) e2, cast(s64) c2); } // 0, 2
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// ── error path: the right tag flows through ──
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c3, e3 := pick("xxx");
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print("error err int = {}\n", cast(s64) e3); // 1
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if e3 == error.Nope { print("error: is Nope (ok)\n"); } else { print("error: not Nope (WRONG)\n"); }
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print("error tag name = {}\n", error_tag_name(e3)); // Nope
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return 0;
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}
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