[Windows] Workaround for making it work in Windows

Sources/_RegexParser/Regex/Parse/CompilerInterface.swift

@@ -107,8 +107,16 @@ public func swiftCompilerParseRegexLiteral(
     // however that it will need plumbing through on the compiler side.
     return (regexToEmit: input, version: currentRegexLiteralFormatVersion)
   } catch {
+    let message: String
+    if
+      let located = error as? Source.LocatedError,
+      let errorDiag = located.error as? Diagnostics.ErrorDiagnostic {
+      message = errorDiag.description
+    } else {
+      message = String(describing: error)
+    }
     throw CompilerParseError(
-      message: "cannot parse regular expression: \(String(describing: error))",
+      message: "cannot parse regular expression: \(message)",
       location: (error as? LocatedErrorProtocol)?.location.start
     )
   }

Sources/_RegexParser/Regex/Parse/Diagnostics.swift

@@ -337,13 +337,14 @@ public struct Diagnostics: Hashable {
     diags.contains(where: { $0.behavior == .fatalError })
   }
 
+  struct ErrorDiagnostic: Error, CustomStringConvertible {
+    var diag: Diagnostic
+    var description: String { diag.message }
+  }
+
   /// If any error diagnostic has been added, throw it as an Error.
   func throwAnyError() throws {
     for diag in diags where diag.isAnyError {
-      struct ErrorDiagnostic: Error, CustomStringConvertible {
-        var diag: Diagnostic
-        var description: String { diag.message }
-      }
       throw Source.LocatedError(ErrorDiagnostic(diag: diag), diag.location)
     }
   }

Sources/_RegexParser/Regex/Parse/SourceLocation.swift

@@ -63,15 +63,15 @@ public protocol LocatedErrorProtocol: Error {
 
 extension Source {
   /// An error that includes information about the location in source code.
-  public struct LocatedError<E: Error>: Error, LocatedErrorProtocol {
-    public let error: E
+  public struct LocatedError: Error, LocatedErrorProtocol {
+    public let error: Error
     public let location: SourceLocation
 
-    init(_ e: E, _ r: SourceLocation) {
+    init(_ e: Error, _ r: SourceLocation) {
       self.error = e
       self.location = r
     }
-    public init(_ v: E, _ r: Range<Source.Position>) {
+    public init(_ v: Error, _ r: Range<Source.Position>) {
       self.error = v
       self.location = Location(r)
     }
@@ -133,6 +133,6 @@ extension Error {
     if self is LocatedErrorProtocol {
       return self
     }
-    return Source.LocatedError<Self>(self, loc)
+    return Source.LocatedError(self, loc)
   }
 }