### **Explanation:**
When a property wrapper's initializer references the enclosing type's
CodingKeys enum (e.g. @Wrapper(key: CodingKeys.bar)), the compiler
enters a dependency cycle: StoredPropertiesRequest →
PropertyWrapperBackingPropertyTypeRequest → ResolveImplicitMemberRequest
(resolve CodingKeys) → ResolveValueWitnessesRequest (Codable
conformance) → StoredPropertiesRequest (cycle).
### **Scope:**
Codable synthesis, property wrappers
### **Issues:**
Fixes#88459
### **Original PRs:**
N/A
### **Risk:**
Low. The change only affects the ResolveCodingKeys path in
ResolveImplicitMemberRequest and is guarded by two conditions: (1)
StoredPropertiesRequest must be active for the same type, and (2) the
user must have explicitly defined a CodingKeys enum. All 74 existing
Codable synthesis tests pass.
### **Testing:**
Added
test/decl/protocol/special/coding/struct_codable_property_wrapper_codingkeys.swift
with 5 test cases: simple wrappers with CodingKeys, custom key mappings,
mixed wrapped/unwrapped properties, Decodable-only, Encodable-only. All
74 Codable tests pass. Runtime encode/decode verified.
### **Reviewers:**
alhafram
2055bc3e76