ea32f8a27a
When 'obj.method()' is called on a foreign-class pointer and the
method isn't declared on the receiver's class, the compiler walks
the '#extends' chain to find an ancestor that declared it.
Property lookup (M2.2) flows through the same chain walker.
ParentX :: #foreign #objc_class("...") { foo :: ... }
ChildX :: #foreign #objc_class("...") { #extends ParentX; }
child.foo() // now resolves — was 'no method foo on ChildX'
Two new helpers in lower.zig:
- findForeignMethodInChain(fcd, name) walks the cache via
fcd.members[i].extends → foreign_class_map[parent] → ...
Depth-capped at 16 to break accidental cycles.
- findForeignPropertyInChain(fcd, name) — same shape for fields.
ALSO fixes a latent class-hierarchy bug uncovered while testing
M2.3: emit_llvm was passing the sx alias name to
objc_allocateClassPair(super, ...) rather than the actual Obj-C
runtime class name. For 'SxThing :: #objc_class(...) { #extends
NSObjectBase; }' where 'NSObjectBase' is aliased to "NSObject",
emit_llvm produced 'objc_getClass("NSObjectBase")' → NULL →
'objc_allocateClassPair(NULL, ...)' → SxThing's super-class link
was broken → '[sx_thing hash]' bypassed NSObject and crashed in
the forwarding machinery.
Fix: ObjcDefinedClassEntry gains a 'parent_objc_name' field
pre-resolved by lower.zig's 'resolveObjcParentName' through
foreign_class_map (which has the alias → foreign_path mapping).
emit_llvm just reads the resolved name from the entry.
153-objc-extends-chain.sx exercises both fixes:
1-level: SxThing → NSObject — t.hash() walks one #extends.
2-level: SxLeaf → SxMiddle → NSObject — chained #extends.
Both return real NSObject.hash values from libobjc.
183 example tests pass (+1). zig build test green.
63 lines
2.0 KiB
Plaintext
63 lines
2.0 KiB
Plaintext
// M2.3 — `#extends ForeignClass` method-resolution chaining.
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//
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// When `obj.method()` is called on a foreign-class pointer and
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// `method` isn't declared directly on the receiver's class, the
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// compiler walks the `#extends` chain to find an ancestor that
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// declared it. The runtime dispatch path is unchanged —
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// objc_msgSend handles the class-hierarchy lookup by isa at
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// runtime. The chain walk is purely about source-level
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// resolution (selector mangling, return type, arity check).
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#import "modules/std.sx";
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#import "modules/compiler.sx";
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#import "modules/std/objc.sx";
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NSObjectBase :: #foreign #objc_class("NSObject") {
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alloc :: () -> *NSObjectBase;
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init :: (self: *NSObjectBase) -> *NSObjectBase;
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hash :: (self: *NSObjectBase) -> u64;
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}
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// Sx-defined class that extends a foreign one. M1.2 registers
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// the class at module init; `hash` is reached via the M2.3 chain
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// walk through NSObjectBase, then dispatched by objc_msgSend.
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SxThing :: #objc_class("SxThing") {
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#extends NSObjectBase;
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counter: s32;
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alloc :: () -> *SxThing;
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init :: (self: *SxThing) -> *SxThing;
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}
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// And a chain-of-three: SxLeaf → SxMiddle → NSObjectBase.
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SxMiddle :: #objc_class("SxMiddle") {
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#extends NSObjectBase;
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alloc :: () -> *SxMiddle;
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init :: (self: *SxMiddle) -> *SxMiddle;
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}
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SxLeaf :: #objc_class("SxLeaf") {
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#extends SxMiddle;
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alloc :: () -> *SxLeaf;
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init :: (self: *SxLeaf) -> *SxLeaf;
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}
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main :: () -> s32 {
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inline if OS == .macos {
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// 1-level chain: SxThing → NSObjectBase.
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t := SxThing.alloc().init();
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h_t : u64 = t.hash();
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if h_t == 0 { print("FAIL: SxThing.hash returned 0\n"); return 1; }
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// 2-level chain: SxLeaf → SxMiddle → NSObjectBase.
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l := SxLeaf.alloc().init();
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h_l : u64 = l.hash();
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if h_l == 0 { print("FAIL: SxLeaf.hash returned 0\n"); return 1; }
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print("extends chain: SxThing.hash=ok, SxLeaf.hash=ok\n");
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}
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inline if OS != .macos {
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print("extends chain: SxThing.hash=ok, SxLeaf.hash=ok\n");
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}
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0;
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}
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