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).
57 lines
1.7 KiB
Plaintext
57 lines
1.7 KiB
Plaintext
// Optional `?f32` fields in struct literals — exhaustively combine null/value
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// for both fields, through both direct calls and protocol dispatch.
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#import "modules/std.sx";
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ProposedSize :: struct {
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width: ?f32;
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height: ?f32;
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}
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// Direct function — does it work?
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direct_size :: (proposal: ProposedSize) -> f32 {
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w := if pw := proposal.width { pw } else { 100.0 };
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h := if ph := proposal.height { ph } else { 100.0 };
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w + h
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}
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Sizable :: protocol {
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size :: (proposal: ProposedSize) -> f32;
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}
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Widget :: struct {}
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impl Sizable for Widget {
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size :: (self: *Widget, proposal: ProposedSize) -> f32 {
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w := if pw := proposal.width { pw } else { 100.0 };
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h := if ph := proposal.height { ph } else { 100.0 };
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w + h
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}
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}
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main :: () -> void {
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// Test 1: Direct call
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print("=== Direct calls ===\n");
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d1 := direct_size(ProposedSize.{ width = 50.0, height = null });
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print("d1 = {}\n", d1);
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d2 := direct_size(ProposedSize.{ width = null, height = 50.0 });
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print("d2 = {}\n", d2);
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d3 := direct_size(ProposedSize.{ width = null, height = null });
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print("d3 = {}\n", d3);
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d4 := direct_size(ProposedSize.{ width = 50.0, height = 60.0 });
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print("d4 = {}\n", d4);
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// Test 2: Protocol dispatch
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print("=== Protocol dispatch ===\n");
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w := Widget.{};
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s : Sizable = w;
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r1 := s.size(ProposedSize.{ width = 50.0, height = null });
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print("r1 = {}\n", r1);
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r2 := s.size(ProposedSize.{ width = null, height = 50.0 });
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print("r2 = {}\n", r2);
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r3 := s.size(ProposedSize.{ width = null, height = null });
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print("r3 = {}\n", r3);
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r4 := s.size(ProposedSize.{ width = 50.0, height = 60.0 });
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print("r4 = {}\n", r4);
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}
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