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).
65 lines
2.5 KiB
Plaintext
65 lines
2.5 KiB
Plaintext
// `catch` on a pure-failable LHS (ERR step E1.5). `expr catch [e] BODY`
|
|
// consumes the error inline: on failure it binds the tag to `e` (optional)
|
|
// and runs BODY; on success the result is void (a `-> !` LHS has no success
|
|
// value). BODY may diverge (`return` / `raise` — typed `noreturn`, E1.4c) or
|
|
// fall through. `catch` needs no failable *enclosing* function — it handles
|
|
// the error locally. All four body forms appear below: block, no-binding
|
|
// block, match-body (`== { case ... }`), and the selective handle + re-raise
|
|
// pattern. Value-carrying `-> (T, !)` catch (binding the success value) lands
|
|
// with the tuple ABI in E2.
|
|
|
|
#import "modules/std.sx";
|
|
|
|
E :: error { Bad, Empty }
|
|
|
|
must :: (n: s32) -> !E {
|
|
if n < 0 { raise error.Bad; }
|
|
if n == 0 { raise error.Empty; }
|
|
return;
|
|
}
|
|
|
|
// Diverging body — returns from `classify` on error.
|
|
classify :: (n: s32) -> s32 {
|
|
must(n) catch (e) {
|
|
if e == error.Bad { return 1; }
|
|
if e == error.Empty { return 2; }
|
|
return 9;
|
|
};
|
|
return 0; // must(n) succeeded
|
|
}
|
|
|
|
// Match-body form — sugar for `catch (e) { if e == { case ... } }`.
|
|
mclassify :: (n: s32) -> s32 {
|
|
must(n) catch (e) == {
|
|
case .Bad: return 11;
|
|
case .Empty: return 22;
|
|
else: return 99;
|
|
};
|
|
return 0;
|
|
}
|
|
|
|
// Selective handle + re-raise (failable enclosing fn; `raise e` is the
|
|
// variable form). Swallows Bad → success; re-raises everything else.
|
|
handle_some :: (n: s32) -> !E {
|
|
must(n) catch (e) {
|
|
if e == error.Bad { return; } // swallow → success
|
|
raise e; // re-raise the rest
|
|
};
|
|
return;
|
|
}
|
|
|
|
main :: () -> s32 {
|
|
r : s32 = 0;
|
|
must(-1) catch (e) { if e == error.Bad { r = r + 1; } }; // Bad → +1
|
|
must(5) catch { r = r + 100; }; // success → body skipped
|
|
r = r + classify(0); // Empty → 2
|
|
r = r + classify(8); // success → 0
|
|
he := handle_some(0); // Empty re-raised
|
|
if he == error.Empty { r = r + 4; } // +4
|
|
hb := handle_some(-1); // Bad swallowed → success
|
|
if hb == error.Bad { r = r + 50; } // not taken
|
|
r = r + mclassify(-1); // Bad → 11
|
|
print("catch result: {}\n", r); // 1+2+4+11 = 18
|
|
return r;
|
|
}
|