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).
98 lines
2.2 KiB
Plaintext
98 lines
2.2 KiB
Plaintext
#import "modules/std.sx";
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// --- Type declarations ---
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OptNode :: struct { value: s32; next: ?s32; }
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OptInner :: struct { val: s32; }
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OptOuter :: struct { inner: ?OptInner; }
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// --- Comptime optionals ---
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ct_sum :: () -> s32 {
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x: ?s32 = 42;
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y: ?s32 = null;
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return (x ?? 0) + (y ?? 99);
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}
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CT_RESULT :: #run ct_sum();
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main :: () -> s32 {
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// Basic optional creation
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x: ?s32 = 42;
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y: ?s32 = null;
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print("x = {}\n", x);
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print("y = {}\n", y);
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// Force unwrap
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print("x! = {}\n", x!);
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// Null coalescing
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print("x ?? 0 = {}\n", x ?? 0);
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print("y ?? 99 = {}\n", y ?? 99);
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// If-binding (safe unwrap)
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if val := x {
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print("if-bind x: {}\n", val);
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}
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if val := y {
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print("should not print\n");
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} else {
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print("if-bind y: none\n");
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}
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// Pattern matching
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check :: (v: ?s32) -> s32 {
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return if v == {
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case .some: (val) { val }
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case .none: { 0 }
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};
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}
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print("match some: {}\n", check(42));
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print("match none: {}\n", check(null));
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// Optional chaining
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p: ?OptNode = OptNode.{ value = 10, next = 20 };
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q: ?OptNode = null;
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print("p?.value = {}\n", p?.value ?? 0);
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print("q?.value = {}\n", q?.value ?? 0);
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// Deep chaining
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o1 := OptOuter.{ inner = OptInner.{ val = 99 } };
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o2 := OptOuter.{ inner = null };
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print("o1.inner?.val = {}\n", o1.inner?.val ?? 0);
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print("o2.inner?.val = {}\n", o2.inner?.val ?? 0);
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// Flow-sensitive narrowing
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a: ?s32 = 10;
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b: ?s32 = 20;
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if a != null {
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print("narrowed a: {}\n", a);
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}
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// Guard narrowing
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guard :: (v: ?s32) -> s32 {
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if v == null { return 0; }
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return v;
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}
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print("guard 42: {}\n", guard(42));
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print("guard null: {}\n", guard(null));
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// Compound narrowing
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if a != null and b != null {
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print("both: {} {}\n", a, b);
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}
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// Compound guard
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guard2 :: (a: ?s32, b: ?s32) -> s32 {
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if a == null or b == null { return 0; }
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return a + b;
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}
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print("guard2: {}\n", guard2(3, 4));
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// Struct field defaults
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n := OptNode.{ value = 10 };
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print("default next: {}\n", n.next);
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// Comptime result
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print("comptime: {}\n", CT_RESULT);
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return 0;
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}
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