Enable existential errors in embedded builds

.github/workflows/pull_request.yml

@@ -35,10 +35,14 @@ jobs:
       enable_windows_checks: false
 
   embedded:
-    name: Embedded Test (Linux nightly-6.3)
+    name: Embedded Test (Linux nightly-${{ matrix.swift_version }})
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        swift_version: ["6.3", "6.4.x"]
     container:
-      image: swiftlang/swift:nightly-6.3-jammy
+      image: swiftlang/swift:nightly-${{ matrix.swift_version }}-jammy
     steps:
       - name: Swift version
         run: swift --version

EmbeddedExample/EmbeddedParser.swift

@@ -24,6 +24,10 @@ struct EmbeddedTest {
 
     precondition(a == 1)
     precondition(b == 0x203)
-    print(c)
+    precondition(c == 0x405)
+    print("Should print '1 / 515 / 1029' on separate lines")
+    print(a)  // 1
+    print(b)  // 515
+    print(c)  // 1029
   }
 }

Sources/BinaryParsing/Parser Types/ParserSource.swift

@@ -107,7 +107,7 @@ public protocol ParserSpanProvider {
 }
 
 extension ParserSpanProvider {
-  #if !$Embedded
+  #if !$Embedded || compiler(>=6.4)
   /// Executes the given closure with a `ParserSpan` over the contents of this
   /// type, consuming the given parser range instead of the full span.
   @_alwaysEmitIntoClient

Sources/BinaryParsing/Parser Types/ParsingError.swift

@@ -49,7 +49,7 @@ public struct ParsingError: Error {
     _location >= 0 ? _location : nil
   }
 
-  #if !$Embedded
+  #if !$Embedded || compiler(>=6.4)
   /// The user-provided error associated with this parsing error.
   public var userError: (any Error)?
 
@@ -78,13 +78,15 @@ public struct ParsingError: Error {
   }
 }
 
-#if !$Embedded
+#if !$Embedded || compiler(>=6.4)
 extension ParsingError {
   public init(userError: any Error) {
     self = .init(status: .userError, userError: userError)
   }
 }
+#endif
 
+#if !$Embedded
 extension ParsingError: CustomStringConvertible {
   public var description: String {
     if let location {
@@ -109,19 +111,20 @@ extension ParsingError.Status: CustomStringConvertible {
 }
 #endif
 
-#if !$Embedded
+#if !$Embedded || compiler(>=6.4)
 /// An error thrown by the library user.
 ///
-/// In a build for non-embedded Swift, `ThrownParsingError` aliases `any Error`,
-/// so you can throw an error of any kind from closures passed to methods that
-/// are designated as `throws(ThrownParsingError)`. When the method throws an
-/// error, it will always be  either your error or an instance of
-/// `ParsingError`.
+/// In a build for non-embedded Swift, or any build using a 6.4 or newer compiler,
+/// `ThrownParsingError` aliases `any Error`, so you can throw an error of
+/// any kind from closures passed to methods that are designated as
+/// `throws(ThrownParsingError)`. When the method throws an error,
+/// it will always be  either your error or an instance of `ParsingError`.
 ///
-/// In a build for embedded Swift, `ThrownParsingError` instead aliases the
-/// specific `ParsingError` type. Because embedded Swift supports only
-/// fully-typed throws, and not the existential `any Error`, this allows you to
-/// still use error-throwing APIs in an embedded context.
+/// In a build for embedded Swift using a pre-6.4 compiler, `ThrownParsingError`
+/// instead aliases the specific `ParsingError` type. Because this version of
+/// embedded Swift supports only fully-typed throws, and not the existential
+/// `any Error`, this allows you to still use error-throwing APIs in an embedded
+/// context.
 public typealias ThrownParsingError = any Error
 #else
 // Documentation is built using the non-embedded build.

Sources/BinaryParsing/Parsers/Array.swift

@@ -44,7 +44,7 @@ extension Array where Element == UInt8 {
 }
 
 extension Array {
-  #if !$Embedded
+  #if !$Embedded || compiler(>=6.4)
   /// Creates a new array by parsing the specified number of elements from the given
   /// parser span, using the provided closure for parsing.
   ///

Sources/BinaryParsing/Parsers/InlineArray.swift

@@ -28,7 +28,7 @@ extension InlineArray where Element == UInt8 {
 
 @available(macOS 26, iOS 26, watchOS 26, tvOS 26, visionOS 26, *)
 extension InlineArray where Element: ~Copyable {
-  #if !$Embedded
+  #if !$Embedded || compiler(>=6.4)
   /// Creates a new array by parsing the specified number of elements from the given
   /// parser span, using the provided closure for parsing.
   ///

Sources/BinaryParsing/Parsers/Range.swift

@@ -12,7 +12,7 @@
 // MARK: Start & Count
 
 extension Range where Bound: FixedWidthInteger {
-  #if !$Embedded
+  #if !$Embedded || compiler(>=6.4)
   /// Creates a new half-open range by parsing the start and count of the range,
   /// using the given parser closure for each value.
   ///
@@ -68,7 +68,7 @@ extension Range where Bound: FixedWidthInteger {
 }
 
 extension ClosedRange where Bound: FixedWidthInteger {
-  #if !$Embedded
+  #if !$Embedded || compiler(>=6.4)
   @available(
     *, deprecated,
     message:
@@ -112,7 +112,7 @@ extension ClosedRange where Bound: FixedWidthInteger {
 // MARK: Start & End
 
 extension Range {
-  #if !$Embedded
+  #if !$Embedded || compiler(>=6.4)
   /// Creates a new half-open range by parsing the start and end of the range,
   /// using the given parser closure for each value.
   ///
@@ -168,7 +168,7 @@ extension Range {
 }
 
 extension ClosedRange {
-  #if !$Embedded
+  #if !$Embedded || compiler(>=6.4)
   /// Creates a new closed range by parsing the start and end of the range,
   /// using the given parser closure for each value.
   ///