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).
26 lines
927 B
Plaintext
26 lines
927 B
Plaintext
// Tuple element assignment + named tuples.
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// - `t.0 = v` writes one element in place (was a known gap: the lvalue path
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// looked the element up by name via getStructFields and left the pointee
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// `.unresolved`; now it indexes the tuple positionally like the read path).
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// - Named tuples `(x: T, y: U)` keep their field names through parsing and
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// type resolution, so `t.x` reads/writes by name (and `.0` by position).
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#import "modules/std.sx";
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main :: () -> s32 {
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// Positional element assignment.
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a : (s32, string) = ---;
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a.0 = 11;
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a.1 = "x";
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print("a: {} {}\n", a.0, a.1);
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// Named tuple: write + read by name, and read by position.
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p : (x: s32, y: string) = ---;
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p.x = 22;
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p.y = "y";
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print("p: x={} y={} .0={}\n", p.x, p.y, p.0);
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p.0 = 33; // position write reaches the same slot as .x
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print("p.x after .0=33: {}\n", p.x);
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0
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}
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