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).
45 lines
1.3 KiB
Plaintext
45 lines
1.3 KiB
Plaintext
// Phase 1.1 — the compiler-internal heap-copy that backs `xx <rvalue>`
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// protocol erasure must dispatch through `context.allocator`, not call
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// libc malloc directly. So when a `push Context.{ allocator = tracer }`
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// block is active, a `xx StructLiteral.{}` inside it MUST be allocated
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// by the tracker.
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//
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// Note: `xx` only heap-copies for RVALUES (struct literals, call results).
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// `xx <lvalue>` (an identifier, field access, index, or deref) borrows
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// the operand's storage, so it never allocates and never reaches this
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// path. See specs.md §3 — Protocol value ownership and lifetime.
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#import "modules/std.sx";
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Tracer :: struct {
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count: s64;
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init :: () -> *Tracer {
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t : *Tracer = xx malloc(size_of(Tracer));
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t.count = 0;
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t
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}
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}
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impl Allocator for Tracer {
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alloc :: (self: *Tracer, size: s64) -> *void {
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self.count += 1;
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return malloc(size);
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}
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dealloc :: (self: *Tracer, ptr: *void) {
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free(ptr);
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}
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}
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ByValue :: struct { x: s64; y: s64; }
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main :: () -> s32 {
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tracer := Tracer.init();
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push Context.{ allocator = xx tracer, data = null } {
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// Struct-literal operand: rvalue → heap-copy through context.allocator.
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ignore : Allocator = xx ByValue.{ x = 1, y = 2 };
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_ = ignore;
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}
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print("Tracer.count = {}\n", tracer.count);
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0
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}
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