2637ae98a5
0164 if <optional> no-binding folds has_value to true (silent miscompile)
0165 parenthesized nested optional ?(?T) malformed double-wrap (crash)
0166 ?? .{ } struct-literal default unresolved type (crash)
0167 comptime regToValue array-in-aggregate gap + unclean recovery
43 lines
1.7 KiB
Markdown
43 lines
1.7 KiB
Markdown
# 0166 — `?? .{ ... }` struct-literal default panics with "unresolved type reached LLVM emission"
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## Symptom
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Using a struct literal as the default of a `??` (null-coalesce) operator panics:
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```
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panic: unresolved type reached LLVM emission
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```
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in `emitStructInit` (exit 134 / SIGABRT). The coalesce result type is inferred
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correctly (the optional's child `T`), but that target type is NOT threaded into
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the RHS struct-literal lowering, so the `struct_init` instruction's `.ty` stays
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`.unresolved` and reaches codegen.
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## Reproduction
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```sx
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#import "modules/std.sx";
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T :: struct { a: i64 = 0; }
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mk :: () -> ?T { return null; }
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main :: () { t := mk() ?? .{ a = 9 }; print("{}\n", t.a); }
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```
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Expected: `9` (null lhs → take the struct-literal default, typed as `T`).
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Observed: `panic: unresolved type reached LLVM emission`, exit 134.
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## Investigation prompt
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The result type IS inferred correctly — `src/ir/expr_typer.zig` (~lines 413–425)
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returns the optional's child `T` for the coalesce expression. The gap is in
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lowering: the `??` RHS struct literal is lowered without a target type. Suspected
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area: `src/ir/lower/expr.zig` `lowerNullCoalesce` (dispatched ~expr.zig:2417)
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must set the lowering target type to the lhs optional's child (`T`) before
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lowering `nc.rhs`, so an untyped `.{ ... }` literal on the RHS resolves to `T`
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the same way an assignment/return target would. Mirror however other contexts
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push an expected type into an untyped struct-literal lowering.
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Verify: the repro prints `9`; also test a present lhs (`mk` returns a value →
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prints the value's field, default not taken) and a nested-field struct literal
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default. Add an `examples/optionals/09xx-null-coalesce-struct-literal.sx`
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regression.
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