bdd0e96d78
A block's value is now its last statement ONLY when that statement is a trailing expression with no `;`. A trailing `;` discards the value, leaving the block void. This makes value-vs-statement explicit and lets the compiler reject "this block was supposed to produce a value". Compiler: - Parser records `Block.produces_value` (last stmt is a no-`;` trailing expression) + `Block.discarded_semi` (the `;` that discarded a value), via `expectSemicolonAfter`. A trailing expression before `}` may now omit its `;` (previously a parse error). Match-arm and else-arm bodies are built value-producing regardless of the arm `;` (arms are exempt — the `;` is an arm terminator). - Lowering: `lowerBlockValue` / the block-expr path / `inferExprType` respect `produces_value`. A value-position block that discards its value is a hard error (`lowerValueBody` for function bodies; the value-context `.block` path for if/else branches, `catch` bodies, value bindings, match arms). Pure-failable `-> !` bodies (value rides the error channel) and a value-if whose branches are void are handled without false errors. - `defer`/`onfail` cleanup bodies lower as statements (void), so a trailing `;` there is fine. Migration (behavior-preserving — output unchanged): - stdlib + ~210 examples: dropped the trailing `;` on value-position last expressions. `format` now ends with an explicit `#insert "return result;"` (it relied on `#insert`-as-block-value, which `;` discards). - Two `main :: () -> s32` examples that relied on the old silent default-return got an explicit trailing `0`. - Rejection snapshots 0412 / 1013 regenerated (their quoted source lines lost a `;`); the diagnostics themselves are unchanged. Docs/tests: specs.md "Block values" section; examples 0040 (rules) + 0041 (rejection); 3 parser unit tests. Filed issue 0066 (pre-existing match-arm negated-literal phi-width quirk, surfaced not caused here). Gates: zig build, zig build test, run_examples.sh -> 343 passed, cross_compile.sh -> 7 passed (also refreshed its stale example names).
47 lines
1.6 KiB
Plaintext
47 lines
1.6 KiB
Plaintext
// Variadic heterogeneous type packs — `..$args` — impl matching
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// lock-in.
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//
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// Step 1d slice for the pack feature (see
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// ~/.claude/plans/lets-see-options-for-merry-dijkstra.md). Pins
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// today's concrete-only impl-matching behaviour: a user-declared
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// `impl Into(Block) for Closure(..$args) -> $R` does NOT match
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// any concrete closure source type. The xx cast site hits the
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// existing "no `Into(Block) for <src>` impl" diagnostic even
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// though the pack impl is reachable.
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//
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// Next commit (1d.B) teaches `tryUserConversion` /
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// `registerParamImpl` to walk a second `param_impl_pack_map`
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// when the concrete-key miss happens. Pack impls bind their
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// `$args` and `$R` to the concrete source closure's tail types
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// and return; monomorphisation proceeds against those bindings.
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//
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// The `Closure(s32, bool) -> bool` shape is not covered by
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// stdlib's hand-rolled impls (only `Closure() -> void` and
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// `Closure(bool) -> void`) and not covered by 96-block-multi-arg's
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// `Closure(s32, *void) -> void` impl, so the pack impl is the
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// only candidate.
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#import "modules/std.sx";
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#import "modules/std/objc_block.sx";
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impl Into(Block) for Closure(..$args) -> $R {
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convert :: (self: Closure(..$args) -> $R) -> Block {
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.{
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isa = @_NSConcreteStackBlock,
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flags = 0,
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reserved = 0,
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invoke = null,
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descriptor = xx @__sx_block_descriptor,
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sx_env = self.env,
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sx_fn = self.fn_ptr,
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}
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}
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}
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main :: () -> s32 {
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cl := (a: s32, b: bool) => true;
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b : *Block = xx cl;
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print("pack impl match ok\n");
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return 0;
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}
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