468461becc
Optional (?T) operands were implicitly unwrapped without proof of
presence, silently miscompiling a NULL ?T to garbage. Unwraps in
binary ops and other expression positions are now gated on flow
narrowing: a ?T value is only auto-unwrapped where control flow has
established it is non-null (the narrowed_refs set). Outside a narrowed
region, an implicit unwrap is rejected rather than producing garbage.
Touches the lowering pipeline (lower.zig + lower/{call,closure,coerce,
comptime,control_flow,expr,ffi,generic,pack,stmt}.zig). Adds optionals
examples 0919-0923 and closures example 0312 covering flow narrowing,
binop narrowing, no-implicit-unwrap rejection, and no closure leak of
narrowed state. Updates specs.md and readme.md.
30 lines
995 B
Plaintext
30 lines
995 B
Plaintext
// Flow narrowing extends to binary-op OPERANDS: a `?T` proven present by a
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// `!= null` guard reads as its concrete payload in arithmetic / comparison.
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//
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// Regression (issue 0185): an un-narrowed `?T` operand used to unwrap
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// unconditionally, so `null + 10` silently yielded `10` (the zero payload).
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// Narrowing is now the only implicit operand unwrap; everything else is a
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// compile error (see 0922).
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#import "modules/std.sx";
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sum :: (a: ?i64, b: ?i64) -> i64 {
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if a == null or b == null { return -1; }
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return a + b; // both operands narrowed
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}
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main :: () {
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x : ?i64 = 30;
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y : ?i64 = 12;
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if x != null and y != null {
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print("add {}\n", x + y); // 42
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print("lt {}\n", x < y); // false
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}
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print("sum 11: {}\n", sum(5, 6)); // 11
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print("sum null: {}\n", sum(5, null)); // -1
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// guard form narrows for the rest of the scope
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n : ?i64 = 9;
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if n == null { return; }
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print("times {}\n", n * 2); // 18
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}
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