TypeRefinementContext validation fails with complicated code in a string interpolation

[DougGregor]

Description

The new validation for TypeRefinementContext is asserting on some code that introduces new contexts within a string interpolation. See example here, the larger context is swiftlang/swift-java#76.

Reproduction

func f() {
  let enumFields: [String] = []
  let s = """
    \(enumFields.map {
      let caseName = $0
      return """
          case .\(caseName):
            if let \(caseName) = classObj.\(caseName) {
              self = \(caseName)
            } else {
              return nil
            }
      """
    }.joined(separator: "\n"))
  """
}


### Stack dump

```text
error: compile command failed due to signal 6 (use -v to see invocation)
child source range not contained
child:
(decl_implicit version=15.0 decl=caseName src_range=[/Users/dgregor/Projects/swift/swift/t.swift:5:7 - line:5:22])parent:
(decl_implicit version=15.0 decl=caseName src_range=[/Users/dgregor/Projects/swift/swift/t.swift:5:7 - line:5:22])Please submit a bug report (https://swift.org/contributing/#reporting-bugs) and include the crash backtrace.
Stack dump:
0.	Program arguments: /Users/dgregor/Projects/swift/build/Ninja-RelWithDebInfoAssert/swift-macosx-arm64/bin/swift-frontend -frontend -c -primary-file /Users/dgregor/Projects/swift/swift/t.swift -target arm64-apple-macosx15.0 -Xllvm -aarch64-use-tbi -enable-objc-interop -color-diagnostics -empty-abi-descriptor -Xcc -working-directory -Xcc /Users/dgregor/Projects/swift/swift -resource-dir /Users/dgregor/Projects/swift/build/Ninja-RelWithDebInfoAssert/swift-macosx-arm64/lib/swift -module-name t -in-process-plugin-server-path /Users/dgregor/Projects/swift/build/Ninja-RelWithDebInfoAssert/swift-macosx-arm64/lib/swift/host/libSwiftInProcPluginServer.dylib -plugin-path /Users/dgregor/Projects/swift/build/Ninja-RelWithDebInfoAssert/swift-macosx-arm64/lib/swift/host/plugins -plugin-path /Users/dgregor/Projects/swift/build/Ninja-RelWithDebInfoAssert/swift-macosx-arm64/local/lib/swift/host/plugins -o /var/folders/ry/cqdwmq3s2k70y0y3b7m9s0_r0000gn/T/TemporaryDirectory.M6hHQM/t-1.o
1.	Swift version 6.1-dev (LLVM 95f3fb07f8f5294, Swift e4d625cbec94d28)
2.	Compiling with effective version 5.10
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
0  swift-frontend           0x0000000109c0cd64 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x0000000109c0b5b0 llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x0000000109c0d394 SignalHandler(int) + 292
3  libsystem_platform.dylib 0x000000018fa38184 _sigtramp + 56
4  libsystem_pthread.dylib  0x000000018fa02f70 pthread_kill + 288
5  libsystem_c.dylib        0x000000018f90f908 abort + 128
6  swift-frontend           0x0000000106647918 verificationError(swift::ASTContext&, llvm::StringRef, std::initializer_list<std::__1::pair<char const*, swift::TypeRefinementContext const*>>) + 196
7  swift-frontend           0x000000010664782c swift::TypeRefinementContext::verify(swift::TypeRefinementContext const*, swift::ASTContext&) const + 556
8  swift-frontend           0x0000000106647644 swift::TypeRefinementContext::verify(swift::TypeRefinementContext const*, swift::ASTContext&) const + 68
9  swift-frontend           0x0000000106647644 swift::TypeRefinementContext::verify(swift::TypeRefinementContext const*, swift::ASTContext&) const + 68
10 swift-frontend           0x00000001063a1b50 swift::verify(swift::SourceFile&) + 116

Expected behavior

This code should be well-formed

Environment

Swift version 6.1-dev (LLVM 95f3fb07f8f5294, Swift e4d625c)

Additional information

No response