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).
80 lines
2.2 KiB
Plaintext
80 lines
2.2 KiB
Plaintext
// Dot-shorthand `.{ child = d }` for a struct whose first field is a protocol
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// value, used as the argument to `List(Container).append` from two distinct
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// container types. Exercises the cross-callsite path of dot-shorthand inference.
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#import "modules/std.sx";
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Drawable :: protocol {
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draw :: () -> s32;
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name :: () -> string;
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layout :: (x: s32) -> s32;
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handle :: (event: s32) -> bool;
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}
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Circle :: struct { radius: s32; }
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impl Drawable for Circle {
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draw :: (self: *Circle) -> s32 { self.radius }
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name :: (self: *Circle) -> string { "circle" }
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layout :: (self: *Circle, x: s32) -> s32 { x + self.radius }
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handle :: (self: *Circle, event: s32) -> bool { event > 0 }
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}
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Square :: struct { side: s32; }
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impl Drawable for Square {
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draw :: (self: *Square) -> s32 { self.side * self.side }
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name :: (self: *Square) -> string { "square" }
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layout :: (self: *Square, x: s32) -> s32 { x + self.side }
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handle :: (self: *Square, event: s32) -> bool { event > 1 }
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}
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Rect :: struct {
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x: f32;
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y: f32;
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w: f32;
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h: f32;
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zero :: () -> Rect { Rect.{ x = 0.0, y = 0.0, w = 0.0, h = 0.0 } }
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}
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Container :: struct {
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child: Drawable;
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computed_frame: Rect = .zero();
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}
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// Two different structs, each with List(Container), both calling .append(.{...})
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// This mirrors VStack/HStack in the game.
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StackA :: struct {
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children: List(Container);
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add :: (self: *StackA, d: Drawable) {
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// BUG: `.{ child = d }` causes LLVM error when 2+ structs do this
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self.children.append(.{ child = d });
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}
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}
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StackB :: struct {
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children: List(Container);
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add :: (self: *StackB, d: Drawable) {
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// BUG: second struct doing `.{ child = d }` triggers the error
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self.children.append(.{ child = d });
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// FIX: explicit `Container.{ child = d }` works
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// self.children.append(Container.{ child = d });
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}
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}
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main :: () -> void {
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c := Circle.{ radius = 42 };
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s := Square.{ side = 5 };
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a : StackA = .{};
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a.add(c);
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print("StackA: draw={}\n", a.children.items[0].child.draw());
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b : StackB = .{};
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b.add(s);
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print("StackB: draw={}\n", b.children.items[0].child.draw());
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print("OK\n");
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}
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