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).
34 lines
1.1 KiB
Plaintext
34 lines
1.1 KiB
Plaintext
// 16-byte integer-only struct passed by value through `#foreign`.
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//
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// emit_llvm.zig's `abiCoerceParamType` routes 9..16-byte non-HFA
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// structs through `[2 x i64]` for register-pair passing on AAPCS64 /
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// SysV AMD64. The call-site side loads the sx struct as `{ i64, i64 }`,
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// so the verifier needs a memory-bitcast bridge in both directions
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// (`abi.struct2arr` on the way in, `abi.arr2struct` on the way back).
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//
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// Different ABI path from 8-byte register-pair structs (coerce to
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// i64), HFAs at the same total size (Vec4f stays a struct), and
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// >16-byte aggregates (passed via pointer + byval).
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//
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// This file was originally filed as issue-0036 (LLVM verifier
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// failure repro). Promoted to a focused feature example once the
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// emit_llvm.zig coerceArg branches landed.
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#import "modules/std.sx";
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#import c {
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#source "1206-ffi-medium-struct.c";
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};
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Pair64 :: struct { a: s64; b: s64; }
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ffi_pair64_swap :: (p: Pair64) -> Pair64 #foreign;
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main :: () -> s32 {
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p : Pair64 = .{ a = 1, b = 2 };
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q := ffi_pair64_swap(p);
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print("swap = ({}, {})\n", q.a, q.b);
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print("ok = {}\n", q.a == 2 and q.b == 1);
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0
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}
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