83ec2536af
try foo() catch (e) { } // legal
try foo() catch e { } // parse error with a migration hint
Same capture style as the for-loop. All four catch shapes keep working
with the parenthesized binding — block, bare-expression body, and the
== match sugar — and the no-binding forms are unchanged. onfail follows
the same rule (onfail (e) { }); its expression-cleanup form is
disambiguated by the paren-group-before-brace lookahead, so
onfail (f()); stays an expression cleanup.
AST unchanged; the printer renders the parens; the #run escape help
text updated. Corpus migrated (57 catch + 3 onfail bindings, in-source
parser test strings, specs incl. grammar rules, readme untouched —
no catch examples there).
Regression: examples/1157-diagnostics-catch-binding-needs-parens.sx;
re-captured stderr for 1010/1013/1037/1123 (migrated source echoed in
carets + help text).
61 lines
2.1 KiB
Plaintext
61 lines
2.1 KiB
Plaintext
// Consuming value-carrying failables with `try` and `catch` (ERR step E2.1b —
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// the consumer side of the error-channel tuple ABI). `try f()` on a
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// `-> (T, !E)` callee binds the value slot on success and propagates the error
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// on failure (a pure-failable caller returns the tag; a value-carrying caller
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// returns `{undef, tag}`). `f() catch (e) BODY` yields the value slot on success
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// or the handler body's value on failure, merged through a block parameter.
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// The producer side is `examples/228-value-failable.sx`.
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#import "modules/std.sx";
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E :: error { Bad, Empty }
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parse :: (n: s32) -> (s32, !E) {
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if n < 0 { raise error.Bad; }
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if n == 0 { raise error.Empty; }
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return n * 2;
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}
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// value-carrying `try` in a value-carrying caller — propagates {undef, tag}.
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inc :: (n: s32) -> (s32, !E) {
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v := try parse(n);
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return v + 1;
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}
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// value-carrying `try` in a pure-failable caller — propagates the tag.
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relay :: (n: s32) -> !E {
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v := try parse(n);
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if v < 0 { raise error.Bad; }
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return;
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}
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// value-carrying `catch`, bare-expression fallback.
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safe :: (n: s32) -> s32 {
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return parse(n) catch (e) 0;
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}
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// value-carrying `catch`, match-body value.
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classify :: (n: s32) -> s32 {
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return parse(n) catch (e) == {
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case .Bad: 1;
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case .Empty: 2;
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else: 3
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};
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}
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main :: () -> s32 {
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r : s32 = 0;
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a, ea := inc(5); // parse(5)=10 → v=10 → 11
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if !ea { r = r + a; } // success → +11 (value live only when proven ok)
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b, eb := inc(-1); // parse(-1)=Bad → propagate {undef, Bad}
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if eb == error.Bad { r = r + 4; } // true → +4
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er := relay(3); // parse(3)=6 ok → relay ok
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if er == error.Bad { r = r + 50; } // false
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r = r + safe(7); // parse(7)=14 → +14
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r = r + safe(-1); // Bad → catch → 0
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r = r + classify(-1); // Bad → 1
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r = r + classify(0); // Empty → 2
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print("consume result: {}\n", r); // 11+4+14+0+1+2 = 32
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return r;
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}
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