Recursive generics cause infinite recursion

Description

Recursive generics cause infinite recursion when deserialising .swiftmodule file.

Reproduction

// badaboom.swift
protocol Tree: AnyObject {}
class TreeBase<Child: Tree> {}
final class AlphaTree: TreeBase<BetaTree>, Tree {}
final class BetaTree: TreeBase<AlphaTree>, Tree {}

# DEBUG_BUILD_DIR=.../swift-project/build/Ninja+cmark-DebugAssert+llvm-RelWithDebInfoAssert+swift-DebugAssert+stdlib-DebugAssert/swift-macosx-arm64
SDKROOT=/Applications/Xcode-15.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk \
    $DEBUG_BUILD_DIR/bin/swiftc \
        -target arm64-apple-macosx10.13 \
        -F /Applications/Xcode-15.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/Library/Frameworks \
        -toolchain-stdlib-rpath \
        -Xlinker \
        -rpath \
        -Xlinker /Applications/Xcode-15.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/Library/Frameworks \
        -Xlinker \
        -rpath \
        -Xlinker /usr/lib/swift \
        -Xlinker \
        -headerpad_max_install_names \
        -swift-version 4 \
        -parse-as-library \
        -F $DEBUG_BUILD_DIR/lib \
        -Xlinker \
        -rpath \
        -Xlinker $DEBUG_BUILD_DIR/lib \
        badaboom.swift \
        -Xfrontend \
        -disable-availability-checking \
        -g \
        -Onone \
        -o ./badaboom.out \
        -module-name main

Stack dump

Please submit a bug report (https://swift.org/contributing/#reporting-bugs) and include the crash backtrace.
Stack dump:
0.  Program arguments: $DEBUG_BUILD_DIR/bin/swift-frontend -frontend -merge-modules -emit-module /var/folders/f6/qllm_pk56m56tdvyx0g_4d3m0000gp/T/badaboom-a1ac7a.swiftmodule -parse-as-library -disable-diagnostic-passes -disable-sil-perf-optzns -target arm64-apple-macosx10.13 -Xllvm -aarch64-use-tbi -enable-objc-interop -sdk /Applications/Xcode-15.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk -F /Applications/Xcode-15.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/Library/Frameworks -F $DEBUG_BUILD_DIR/lib -g -swift-version 4 -Onone -disable-availability-checking -enable-anonymous-context-mangled-names -external-plugin-path /Applications/Xcode-15.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib/swift/host/plugins#/Applications/Xcode-15.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/bin/swift-plugin-server -external-plugin-path /Applications/Xcode-15.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/local/lib/swift/host/plugins#/Applications/Xcode-15.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/bin/swift-plugin-server -external-plugin-path /Applications/Xcode-15.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib/swift/host/plugins#/Applications/Xcode-15.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server -external-plugin-path /Applications/Xcode-15.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/local/lib/swift/host/plugins#/Applications/Xcode-15.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server -plugin-path $DEBUG_BUILD_DIR/lib/swift/host/plugins -plugin-path $DEBUG_BUILD_DIR/local/lib/swift/host/plugins -target-sdk-version 14.0 -dwarf-version=4 -emit-module-doc-path /var/folders/f6/qllm_pk56m56tdvyx0g_4d3m0000gp/T/main-091c70.swiftdoc -emit-module-source-info-path /var/folders/f6/qllm_pk56m56tdvyx0g_4d3m0000gp/T/main-091c70.swiftsourceinfo -module-name main -o /var/folders/f6/qllm_pk56m56tdvyx0g_4d3m0000gp/T/main-091c70.swiftmodule
1.  Swift version 5.11-dev (LLVM 8be112bb7e107a9, Swift df858a5ab96c574)
2.  Compiling with effective version 4.1.50
3.  While evaluating request ExecuteSILPipelineRequest(Run pipelines { Non-Diagnostic Mandatory Optimizations, Serialization, Rest of Onone } on SIL for main)
4.  While running pass #1 SILModuleTransform "SerializeSILPass".
5.  While reading from module 'main', builder version '5.11(4.1.50)/Swift version 5.11-dev (LLVM 8be112bb7e107a9, Swift df858a5ab96c574)', built from source, non-resilient, loaded from '/var/folders/f6/qllm_pk56m56tdvyx0g_4d3m0000gp/T/badaboom-a1ac7a.swiftmodule'
6.  While deserializing decl @ 124968 (CLASS_DECL) in 'main'
7.      ...decl is named 'AlphaTree'
8.  While deserializing decl @ 125436 (CLASS_DECL) in 'main'
9.      ...decl is named 'BetaTree'
10. While deserializing decl @ 124968 (CLASS_DECL) in 'main'
11.     ...decl is named 'AlphaTree'
12. While deserializing decl @ 125436 (CLASS_DECL) in 'main'
13.     ...decl is named 'BetaTree'
14. While deserializing decl @ 124968 (CLASS_DECL) in 'main'
15.     ...decl is named 'AlphaTree'
...
2684.   While deserializing decl @ 125436 (CLASS_DECL) in 'main'
2685.       ...decl is named 'BetaTree'
2686.   While deserializing decl @ 124968 (CLASS_DECL) in 'main'
2687.       ...decl is named 'AlphaTree'
<unknown>:0: error: unable to execute command: Segmentation fault: 11
<unknown>:0: error: merge-module command failed due to signal 11 (use -v to see invocation)

Expected behavior

No crash. Ideally code should not be rejected as invalid, but if this is not possible, compilation error would be better than crash.

Environment

Swift version 5.11-dev (LLVM 8be112bb7e107a9, Swift df858a5ab96c574) Target: arm64-apple-macosx10.13

Additional information

No response

swiftlang / swift

Recursive generics cause infinite recursion #70625