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).
60 lines
2.1 KiB
Plaintext
60 lines
2.1 KiB
Plaintext
// Phase 0 baseline (PLAN-FFI.md step 0.6): sx function passed to C
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// as a function pointer; C invokes it; sx-side observable effect.
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// Mirrors the `app->onInputEvent` install pattern in
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// library/modules/platform/android.sx.
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//
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// Two arities covered:
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// 1. (s32) -> s32 — single-arg callback
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// 2. (*void, s32) -> s32 — pointer + value (onInputEvent shape)
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//
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// Plus a side-effect via a global so we can confirm the callback
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// actually fired (return value + state mutation both observable).
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#import "modules/std.sx";
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#import c {
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#source "1214-ffi-06-callback.c";
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};
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ffi_apply_callback :: (cb: (s32) -> s32 callconv(.c), value: s32) -> s32 #foreign;
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ffi_apply_callback2 :: (cb: (*void, s32) -> s32 callconv(.c), ctx: *void, v: s32) -> s32 #foreign;
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g_callback_hits : s32 = 0;
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g_callback_sum : s32 = 0;
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double_it :: (x: s32) -> s32 callconv(.c) {
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g_callback_hits += 1;
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g_callback_sum += x;
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x * 2
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}
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add_with_ctx :: (ctx: *void, v: s32) -> s32 callconv(.c) {
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g_callback_hits += 1;
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// Pass a sentinel via ctx to prove the pointer arg also survives the
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// round-trip — read it back as an s32 through *s32.
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p : *s32 = xx ctx;
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p.* + v
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}
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main :: () -> s32 {
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// ── Single-arg callback ────────────────────────────────────────
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r1 := ffi_apply_callback(double_it, 21);
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print("callback returned = {}\n", r1);
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print("hits after first call = {}\n", g_callback_hits);
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print("sum after first call = {}\n", g_callback_sum);
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// Two more calls confirm the same fn pointer keeps working.
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ffi_apply_callback(double_it, 7);
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ffi_apply_callback(double_it, 11);
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print("hits after three calls = {}\n", g_callback_hits);
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print("sum after three calls = {}\n", g_callback_sum);
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// ── Two-arg callback with opaque ctx pointer ───────────────────
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ctx_val : s32 = 100;
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r2 := ffi_apply_callback2(add_with_ctx, xx @ctx_val, 42);
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print("ctx + value = {}\n", r2);
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print("hits after ctx callback = {}\n", g_callback_hits);
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0
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}
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