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).
93 lines
2.2 KiB
Plaintext
93 lines
2.2 KiB
Plaintext
#import "modules/std.sx";
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#import "modules/math/math.sx";
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#import "modules/compiler.sx";
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#import "modules/test.sx";
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pkg :: #import "modules/testpkg";
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Point :: struct { x, y: s32; }
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add :: (a: s32, b: s32) -> s32 { a + b }
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Counter :: protocol {
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inc :: ();
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get :: () -> s32;
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}
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Summable :: protocol {
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sum :: () -> s32;
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}
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SimpleCounter :: struct { val: s32; }
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impl Counter for SimpleCounter {
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inc :: (self: *SimpleCounter) { self.val += 1; }
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get :: (self: *SimpleCounter) -> s32 { self.val }
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}
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impl Summable for Point {
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sum :: (self: *Point) -> s32 { self.x + self.y }
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}
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// Phase 2: #inline protocol for dynamic dispatch
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// Phase 2: #inline protocol for dynamic dispatch
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Adder :: protocol #inline {
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add :: (n: s32);
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value :: () -> s32;
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}
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Accumulator :: struct {
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total: s32;
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}
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impl Adder for Accumulator {
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add :: (self: *Accumulator, n: s32) { self.total += n; }
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value :: (self: *Accumulator) -> s32 { self.total }
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}
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main :: () {
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// --- Auto type erasure (AE) ---
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print("=== Auto Type Erasure ===\n");
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// AE1: function argument — concrete passed where protocol expected (no xx)
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{
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use_counter :: (c: Counter) -> s32 { c.inc(); c.inc(); c.get() }
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sc := SimpleCounter.{ val = 10 };
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result := use_counter(sc);
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print("AE1: {}\n", result);
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}
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// AE2: variable assignment — concrete to protocol variable (no xx)
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{
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acc := Accumulator.{ total = 0 };
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a: Adder = acc;
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a.add(5);
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a.add(3);
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print("AE2: {}\n", a.value());
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}
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// AE3: struct literal passed directly (no xx)
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{
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use_counter :: (c: Counter) -> s32 { c.inc(); c.inc(); c.get() }
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result := use_counter(SimpleCounter.{ val = 100 });
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print("AE3: {}\n", result);
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}
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// AE4: explicit xx still works (not broken)
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{
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use_counter :: (c: Counter) -> s32 { c.inc(); c.get() }
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result := use_counter(xx SimpleCounter.{ val = 50 });
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print("AE4: {}\n", result);
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}
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// AE5: pointer auto-erasure — *ConcreteType to protocol
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{
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use_adder :: (a: Adder) { a.add(10); }
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acc := Accumulator.{ total = 5 };
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p := @acc;
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use_adder(p);
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print("AE5: {}\n", acc.total);
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}
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}
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