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).
41 lines
1.6 KiB
Plaintext
41 lines
1.6 KiB
Plaintext
// Error return-trace buffer push/clear wiring (ERR step E3.2). A `raise` and a
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// propagating `try` each push a frame; an absorbing site (`catch`, `or value`,
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// a destructure that binds the error) clears the buffer. In debug builds
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// (`sx run` defaults to -O0) these calls are emitted; in release they're
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// skipped entirely (zero overhead). Until E3.3 ships `trace.print_current`,
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// this example observes the buffer directly via the runtime's `sx_trace_len`
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// (linked in for the JIT) — a white-box probe, not the eventual public API.
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#import "modules/std.sx";
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// Internal runtime symbol (library/vendors/sx_trace_runtime/sx_trace.c).
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sx_trace_len :: () -> u32 #foreign;
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E :: error { Bad }
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fail :: (n: s32) -> !E {
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if n < 0 { raise error.Bad; } // pushes a frame
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return;
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}
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propagate :: (n: s32) -> !E {
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try fail(n); // on failure: pushes a frame, propagates
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return;
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}
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main :: () -> s32 {
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// `catch` lets the handler INSPECT the trace, then absorbs: the buffer is
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// cleared when the handler completes (a non-diverging exit), not on entry.
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// So inside the handler the frames are still visible (here: the `raise` in
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// `fail` + the `try fail` propagation in `propagate` = 2 frames)...
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propagate(-1) catch (e) {
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print("in catch: len={}\n", sx_trace_len()); // 2 (handler sees the chain)
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};
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print("after catch: len={}\n", sx_trace_len()); // 0 (absorbed at handler exit)
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// A success leaves the buffer empty (nothing pushed).
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propagate(1) catch (e) { };
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print("after success: len={}\n", sx_trace_len()); // 0
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return 0;
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}
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