test(C0.2): pin curated-bindings shape — #source-only unit + hand #foreign works (JIT+AOT), but the ref is decorative (xfail for C3.1)

examples/1619-cimport-source-only.sx

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+// Pins the curated-bindings shape (PLAN-C C0.2): a `#source`-only unit
+// (no `#include`, so no auto-synthesized decls) paired with a
+// hand-written `#foreign` decl naming the unit. Works in JIT and AOT
+// today — but see 1620: the unit ref is not yet validated or scoped,
+// so the symbol actually resolves globally, not through the unit.
+#import "modules/std.sx";
+
+only :: #import c {
+    #source "1619-cimport-source-only/only.c";
+};
+
+only_answer :: () -> i32 #foreign only "only_answer";
+
+main :: () -> i32 {
+    print("answer = {}\n", only_answer() + 1);
+    0
+}

examples/1619-cimport-source-only/only.c

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+int only_answer(void) { return 41; }

examples/1620-cimport-foreign-ref-unvalidated.sx

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+// Pins the C3 gap (PLAN-C C0.2b): the `#foreign` library/unit ref is
+// DECORATIVE today — `nosuchunit` names nothing anywhere, yet this
+// compiles and the symbol resolves globally (the unit's objects are in
+// the program; the ref is never consulted). After C3 this is a
+// compile-time diagnostic: a #foreign ref must name a #library or a
+// named `#import c` unit.
+#import "modules/std.sx";
+
+refs :: #import c {
+    #source "1620-cimport-foreign-ref-unvalidated/ref.c";
+};
+
+ref_answer :: () -> i32 #foreign nosuchunit "ref_answer";
+
+main :: () -> i32 {
+    print("ref = {}\n", ref_answer());
+    0
+}

examples/1620-cimport-foreign-ref-unvalidated/ref.c

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+int ref_answer(void) { return 7; }

examples/expected/1619-cimport-source-only.exit

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+0

examples/expected/1619-cimport-source-only.stderr

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+

examples/expected/1619-cimport-source-only.stdout

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+answer = 42

examples/expected/1620-cimport-foreign-ref-unvalidated.exit

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+0

examples/expected/1620-cimport-foreign-ref-unvalidated.stderr

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+

examples/expected/1620-cimport-foreign-ref-unvalidated.stdout

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+ref = 7