Files
sx/examples/1041-errors-failable-closure-shape-union.sx
agra 39c21468ee ERR/E5.1: program-wide inferred-! union per closure/fn shape
All occurrences of Closure(<sig>) -> (T, !) with a structurally identical
value-signature now share one inferred error-set node; every bare-!
closure literal of that shape unions its escape tags in, and a
`try slot(x)` against any matching-shape slot widens the caller's named
set against that union. This closes the gap where a slot call (no static
function name) skipped the widening check entirely.

- shape_inferred_sets keyed by closureShapeKey (params + value-return via
  mangleTypeName, error slot excluded) so bare-!, non-failable, .function
  and .closure of one value-sig collapse to a single key.
- convergeClosureShapeSets pre-pass (lowerRoot Pass 1d', after the
  name-keyed convergeInferredErrorSets): collectClosureShapes walks fn
  bodies through lambda boundaries; recordClosureShape resolves each
  concrete bare-! literal's shape and unions its raises (+ try named_fn()
  edges via calleeEscapeTags) into the shape node.
- checkEscapeWidening falls back to shapeKeyOfCallee for bare-! slot calls
  (computed from the callee expr's .function/.closure type). Empty union
  is silently allowed (sub-feature 6).

Scope: concrete shapes only (generic lambdas skipped); closure-to-closure
try edges are not fix-pointed (under-approximation = a missed diagnostic,
never a miscompile).

Tests: 1041 (positive — union composes, runs), 1042 (reject — two
widening diagnostics, exit 1).
2026-06-01 22:01:38 +03:00

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// Program-wide inferred-`!` union per closure shape (ERR E5.1 sub-feature 2).
// All occurrences of `Closure(s32) -> (s32, !)` share ONE inferred error set;
// every bare-`!` closure literal of that shape unions its raised tags in. A
// `try slot(x)` against any matching-shape slot widens against that union — so
// a caller whose named set covers { Negative, Other } type-checks, and the
// error channel actually carries each closure's own tag at runtime.
#import "modules/std.sx";
All :: error { Negative, Other }
// `h` is a bare-`!` Closure slot; the caller declares the union as `!All`.
dispatch :: (h: Closure(s32) -> (s32, !), x: s32) -> (s32, !All) {
return try h(x);
}
main :: () -> s32 {
gpa := GPA.init();
push Context.{ allocator = xx gpa } {
// Two literals of the SAME shape raising DIFFERENT tags both feed the
// one shared `Closure(s32)->(s32,!)` union node.
handlers : List(Closure(s32) -> (s32, !)) = .{};
handlers.append(closure((x: s32) -> (s32, !) { if x < 0 { raise error.Negative; } return x * 2; }));
handlers.append(closure((x: s32) -> (s32, !) { if x == 0 { raise error.Other; } return x + 100; }));
// success paths
print("ok0={}\n", dispatch(handlers.items[0], 5) catch e 0); // 10
print("ok1={}\n", dispatch(handlers.items[1], 7) catch e 0); // 107
// failure paths: each closure raises its own tag, which propagates
// through `try` and is absorbed by the call-site `catch` fallback
print("err0={}\n", dispatch(handlers.items[0], -1) catch e -1); // raised Negative → -1
print("err1={}\n", dispatch(handlers.items[1], 0) catch e -2); // raised Other → -2
}
return 0;
}