[C++ Interop] generated header contains ambiguous overloads / redefinitions

[tothambrus11]

Description

When enabling C++ interop in my module and using its generated header file from C++, the header appears to contain redefinition of functions.

Reproduction

CI Run (look at ubuntu): https://github.com/hylo-lang/hylo-new/actions/runs/21786807627/job/62859520288?pr=40

See the reproduction in this PR: https://github.com/hylo-lang/hylo-new/pull/41/changes

I attached the generated header file: FrontEnd-Swift.h.txt

In file included from /home/runner/work/hylo-new/hylo-new/Sources/LLVMEmitter/include/Example.cpp:1:
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:6985:53: error: functions that differ only in their return type cannot be overloaded
 6985 |   SWIFT_INLINE_THUNK swift::Optional<swift::String> getString() const SWIFT_SYMBOL("s:8FrontEnd10AnnotationV8ArgumentO6stringSSSgvp");
      |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:6965:36: note: previous declaration is here
 6965 |   SWIFT_INLINE_THUNK swift::String getString() const;
      |                      ~~~~~~~~~~~~~ ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:6986:50: error: functions that differ only in their return type cannot be overloaded
 6986 |   SWIFT_INLINE_THUNK swift::Optional<swift::Int> getNumber() const SWIFT_SYMBOL("s:8FrontEnd10AnnotationV8ArgumentO6numberSiSgvp");
      |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:6974:33: note: previous declaration is here
 6974 |   SWIFT_INLINE_THUNK swift::Int getNumber() const;
      |                      ~~~~~~~~~~ ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:7308:47: error: class member cannot be redeclared
 7308 |   static SWIFT_INLINE_THUNK AnySyntaxIdentity init(uint64_t value) SWIFT_SYMBOL("s:8FrontEnd17AnySyntaxIdentityV14integerLiteralACs6UInt64V_tcfc");
      |                                               ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:7298:47: note: previous declaration is here
 7298 |   static SWIFT_INLINE_THUNK AnySyntaxIdentity init(uint64_t bits) SWIFT_SYMBOL("s:8FrontEnd17AnySyntaxIdentityV4bitsACs6UInt64V_tcfc");
      |                                               ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:7465:45: error: class member cannot be redeclared
 7465 |   static SWIFT_INLINE_THUNK AnyTypeIdentity init(uint64_t value) SWIFT_SYMBOL("s:8FrontEnd15AnyTypeIdentityV14integerLiteralACs6UInt64V_tcfc");
      |                                             ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:7451:45: note: previous declaration is here
 7451 |   static SWIFT_INLINE_THUNK AnyTypeIdentity init(uint64_t bits) SWIFT_SYMBOL("s:8FrontEnd15AnyTypeIdentityV4bitsACs6UInt64V_tcfc");
      |                                             ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:14076:69: error: class member cannot be redeclared
 14076 |   static SWIFT_INLINE_THUNK swift::Optional<FloatingPointPredicate> init(const swift::String& description) SWIFT_SYMBOL("s:8FrontEnd22FloatingPointPredicateOyACSgSScfc");
       |                                                                     ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:14074:69: note: previous declaration is here
 14074 |   static SWIFT_INLINE_THUNK swift::Optional<FloatingPointPredicate> init(const swift::String& rawValue) SWIFT_SYMBOL("s:8FrontEnd22FloatingPointPredicateO8rawValueACSgSS_tcfc");
       |                                                                     ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:19990:63: error: class member cannot be redeclared
 19990 |   static SWIFT_INLINE_THUNK swift::Optional<IntegerPredicate> init(const swift::String& description) SWIFT_SYMBOL("s:8FrontEnd16IntegerPredicateOyACSgSScfc");
       |                                                               ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:19988:63: note: previous declaration is here
 19988 |   static SWIFT_INLINE_THUNK swift::Optional<IntegerPredicate> init(const swift::String& rawValue) SWIFT_SYMBOL("s:8FrontEnd16IntegerPredicateO8rawValueACSgSS_tcfc");
       |                                                               ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:26103:40: error: class member cannot be redeclared
 26103 |   static SWIFT_INLINE_THUNK SourceFile init(const swift::String& contents) SWIFT_SYMBOL("s:8FrontEnd10SourceFileV13stringLiteralACSS_tcfc");
       |                                        ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:26084:40: note: previous declaration is here
 26084 |   static SWIFT_INLINE_THUNK SourceFile init(const swift::String& contents) SWIFT_SYMBOL("s:8FrontEnd10SourceFileV8contentsACSS_tcfc");
       |                                        ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:32247:83: error: return type of out-of-line definition of 'FrontEnd::__AnnotationNested::Argument::getString' differs from that in the declaration
 32247 |   SWIFT_INLINE_THUNK swift::Optional<swift::String> __AnnotationNested::Argument::getString() const {
       |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                               ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:32220:66: note: previous definition is here
 32220 |   SWIFT_INLINE_THUNK swift::String __AnnotationNested::Argument::getString() const {
       |                      ~~~~~~~~~~~~~                               ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:32252:80: error: return type of out-of-line definition of 'FrontEnd::__AnnotationNested::Argument::getNumber' differs from that in the declaration
 32252 |   SWIFT_INLINE_THUNK swift::Optional<swift::Int> __AnnotationNested::Argument::getNumber() const {
       |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~                               ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:32238:63: note: previous definition is here
 32238 |   SWIFT_INLINE_THUNK swift::Int __AnnotationNested::Argument::getNumber() const {
       |                      ~~~~~~~~~~                               ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:32315:59: error: redefinition of 'init'
 32315 |   SWIFT_INLINE_THUNK AnySyntaxIdentity AnySyntaxIdentity::init(uint64_t value) {
       |                                                           ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:32281:59: note: previous definition is here
 32281 |   SWIFT_INLINE_THUNK AnySyntaxIdentity AnySyntaxIdentity::init(uint64_t bits) {
       |                                                           ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:32380:55: error: redefinition of 'init'
 32380 |   SWIFT_INLINE_THUNK AnyTypeIdentity AnyTypeIdentity::init(uint64_t value) {
       |                                                       ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:32328:55: note: previous definition is here
 32328 |   SWIFT_INLINE_THUNK AnyTypeIdentity AnyTypeIdentity::init(uint64_t bits) {
       |                                                       ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:33706:86: error: redefinition of 'init'
 33706 |   SWIFT_INLINE_THUNK swift::Optional<FloatingPointPredicate> FloatingPointPredicate::init(const swift::String& description) {
       |                                                                                      ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:33693:86: note: previous definition is here
 33693 |   SWIFT_INLINE_THUNK swift::Optional<FloatingPointPredicate> FloatingPointPredicate::init(const swift::String& rawValue) {
       |                                                                                      ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:34692:74: error: redefinition of 'init'
 34692 |   SWIFT_INLINE_THUNK swift::Optional<IntegerPredicate> IntegerPredicate::init(const swift::String& description) {
       |                                                                          ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:34679:74: note: previous definition is here
 34679 |   SWIFT_INLINE_THUNK swift::Optional<IntegerPredicate> IntegerPredicate::init(const swift::String& rawValue) {
       |                                                                          ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:36217:45: error: redefinition of 'init'
 36217 |   SWIFT_INLINE_THUNK SourceFile SourceFile::init(const swift::String& contents) {
       |                                             ^
/home/runner/work/hylo-new/hylo-new/.build/x86_64-unknown-linux-gnu/debug/FrontEnd.build/include/FrontEnd-Swift.h:36160:45: note: previous definition is here
 36160 |   SWIFT_INLINE_THUNK SourceFile SourceFile::init(const swift::String& contents) {
       |                                             ^
14 errors generated.
error: fatalError

Expected behavior

No redefined functions.

Environment

Swift version 6.2.3 (swift-6.2.3-RELEASE)
Target: x86_64-unknown-linux-gnu

Additional information

No response