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).
86 lines
2.8 KiB
Plaintext
86 lines
2.8 KiB
Plaintext
// Match expression with both `null` arms and concrete struct value arms
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// produces an optional type (?T) and correctly wraps non-null values.
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#import "modules/std.sx";
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HAlignment :: enum { leading; center; trailing; }
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VAlignment :: enum { top; center; bottom; }
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Alignment :: struct { h: HAlignment; v: VAlignment; }
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ALIGN_CENTER :: Alignment.{ h = .center, v = .center };
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ALIGN_TOP :: Alignment.{ h = .center, v = .top };
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ALIGN_BOTTOM :: Alignment.{ h = .center, v = .bottom };
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ALIGN_LEADING :: Alignment.{ h = .leading, v = .center };
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ALIGN_TRAILING :: Alignment.{ h = .trailing, v = .center };
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ALIGN_TOP_LEADING :: Alignment.{ h = .leading, v = .top };
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ALIGN_TOP_TRAILING :: Alignment.{ h = .trailing, v = .top };
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ALIGN_BOTTOM_LEADING :: Alignment.{ h = .leading, v = .bottom };
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ALIGN_BOTTOM_TRAILING :: Alignment.{ h = .trailing, v = .bottom };
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Zone :: enum {
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floating;
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fill;
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center;
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top;
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bottom;
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left;
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right;
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top_left;
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top_right;
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bottom_left;
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bottom_right;
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}
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// Match expression as implicit return with mixed null/concrete arms
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zone_to_alignment :: (zone: Zone) -> ?Alignment {
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if zone == {
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case .floating: null;
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case .fill: ALIGN_CENTER;
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case .center: ALIGN_CENTER;
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case .top: ALIGN_TOP;
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case .bottom: ALIGN_BOTTOM;
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case .left: ALIGN_LEADING;
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case .right: ALIGN_TRAILING;
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case .top_left: ALIGN_TOP_LEADING;
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case .top_right: ALIGN_TOP_TRAILING;
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case .bottom_left: ALIGN_BOTTOM_LEADING;
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case .bottom_right: ALIGN_BOTTOM_TRAILING;
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}
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}
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// Side-effect match inside a function returning bool — must NOT be
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// affected by optional inference (no null arms here)
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NodeType :: enum { rect; text; image; }
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process_node :: (t: NodeType) -> bool {
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if t == {
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case .rect: { out("rect\n"); }
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case .text: { out("text\n"); }
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case .image: { out("image\n"); }
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}
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true
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}
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main :: () -> void {
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// Test null arm
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r0 := zone_to_alignment(.floating);
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if a := r0 { print("BUG: floating should be null, got h={}\n", xx a.h); }
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else { out("ok: floating is null\n"); }
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// Test concrete arms
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r1 := zone_to_alignment(.left);
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if a := r1 { print("ok: left h={}\n", xx a.h); }
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else { out("BUG: left returned null\n"); }
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r2 := zone_to_alignment(.center);
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if a := r2 { print("ok: center h={}\n", xx a.h); }
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else { out("BUG: center returned null\n"); }
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r3 := zone_to_alignment(.top_right);
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if a := r3 { print("ok: top_right h={} v={}\n", xx a.h, xx a.v); }
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else { out("BUG: top_right returned null\n"); }
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// Test side-effect match (no null arms) still works
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process_node(.rect);
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process_node(.text);
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}
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