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).
31 lines
786 B
Plaintext
31 lines
786 B
Plaintext
// impl Protocol for built-in scalar types (f32, s64, bool, u32, ...) —
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// both static dispatch (`f32.lerp(...)`) and protocol-boxed dispatch via
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// `#inline` erasure.
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Lerpable :: protocol #inline {
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lerp :: (b: Self, t: f32) -> Self;
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}
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impl Lerpable for f32 {
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lerp :: (self: f32, b: f32, t: f32) -> f32 { self + (b - self) * t }
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}
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do_lerp :: (a: Lerpable, b: f32, t: f32) -> f32 {
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a.lerp(b, t)
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}
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main :: () -> void {
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// Static call through impl
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result := f32.lerp(0.0, 10.0, 0.5);
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print("lerp(0, 10, 0.5) = {}\n", result);
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// Protocol dispatch through #inline erasure
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val : f32 = 0.0;
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p : *f32 = @val;
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l : Lerpable = xx p;
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result2 := do_lerp(l, 10.0, 0.25);
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print("lerp(0, 10, 0.25) = {}\n", result2);
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}
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#import "modules/std.sx";
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