Minor fixes for SwiftIfConfig

Sources/SwiftIfConfig/IfConfigEvaluation.swift

@@ -109,12 +109,12 @@ func evaluateIfConfig(
   if let prefixOp = condition.as(PrefixOperatorExprSyntax.self),
     prefixOp.operator.text == "!"
   {
-    let (innerActive, innersyntaxErrorsAllowed, innerDiagnostics) = evaluateIfConfig(
+    let (innerActive, innerSyntaxErrorsAllowed, innerDiagnostics) = evaluateIfConfig(
       condition: prefixOp.expression,
       configuration: configuration
     )
 
-    return (active: !innerActive, syntaxErrorsAllowed: innersyntaxErrorsAllowed, diagnostics: innerDiagnostics)
+    return (active: !innerActive, syntaxErrorsAllowed: innerSyntaxErrorsAllowed, diagnostics: innerDiagnostics)
   }
 
   // Logical '&&' and '||'.
@@ -334,13 +334,7 @@ func evaluateIfConfig(
         let segment = stringLiteral.segments.first,
         case .stringSegment(let stringSegment) = segment
       else {
-        return recordError(
-          .requiresUnlabeledArgument(
-            name: "_compiler_version",
-            role: "version",
-            syntax: ExprSyntax(call)
-          )
-        )
+        return doVersionComparisonCheck(configuration.compilerVersion)
       }
 
       let versionString = stringSegment.content.text

Sources/SwiftIfConfig/IfConfigRegionState.swift

@@ -25,12 +25,12 @@ public enum IfConfigRegionState {
   case active
 
   /// Evaluate the given `#if` condition using the given build configuration
-  /// to determine its state and identify any problems encountered along the
-  /// way.
+  /// to determine its state, whether syntax errors in inactive conditions are
+  /// permitted, and to identify any problems encountered along the way.
   public static func evaluating(
     _ condition: some ExprSyntaxProtocol,
     in configuration: some BuildConfiguration
-  ) -> (state: IfConfigRegionState, diagnostics: [Diagnostic]) {
+  ) -> (state: IfConfigRegionState, syntaxErrorsAllowed: Bool, diagnostics: [Diagnostic]) {
     // Apply operator folding for !/&&/||.
     var foldingDiagnostics: [Diagnostic] = []
     let foldedCondition = OperatorTable.logicalOperators.foldAll(condition) { error in
@@ -44,9 +44,9 @@ public enum IfConfigRegionState {
 
     let diagnostics = foldingDiagnostics + evalDiagnostics
     switch (active, syntaxErrorsAllowed) {
-    case (true, _): return (.active, diagnostics)
-    case (false, false): return (.inactive, diagnostics)
-    case (false, true): return (.unparsed, diagnostics)
+    case (true, _): return (.active, syntaxErrorsAllowed, diagnostics)
+    case (false, false): return (.inactive, syntaxErrorsAllowed, diagnostics)
+    case (false, true): return (.unparsed, syntaxErrorsAllowed, diagnostics)
     }
   }
 }

Sources/SwiftIfConfig/VersionTuple+Parsing.swift

@@ -27,7 +27,7 @@ extension VersionTuple {
     components = []
 
     // Version value are separated by periods.
-    let componentStrings = versionString.split(separator: ".")
+    let componentStrings = versionString.split(separator: ".", omittingEmptySubsequences: false)
 
     /// Record a component after checking its value.
     func recordComponent(_ value: Int) throws {

Sources/SwiftIfConfig/VersionTuple.swift

@@ -33,7 +33,7 @@ public struct VersionTuple: Sendable {
   public init?(parsing string: String) {
     self.components = []
 
-    for componentText in string.split(separator: ".") {
+    for componentText in string.split(separator: ".", omittingEmptySubsequences: false) {
       guard let component = Int(componentText) else {
         return nil
       }

Tests/SwiftIfConfigTest/EvaluateTests.swift

@@ -176,12 +176,25 @@ public class EvaluateTests: XCTestCase {
     assertIfConfig("swift(>=5.5)", .active)
     assertIfConfig("swift(<6)", .active)
     assertIfConfig("swift(>=6)", .unparsed)
+    assertIfConfig(
+      "swift(>=...)",
+      .unparsed,
+      diagnostics: [
+        DiagnosticSpec(
+          message: "'swift' version check has invalid version ''",
+          line: 1,
+          column: 9
+        )
+      ]
+    )
     assertIfConfig("compiler(>=5.8)", .active)
     assertIfConfig("compiler(>=5.9)", .active)
     assertIfConfig("compiler(>=5.10)", .unparsed)
     assertIfConfig(#"_compiler_version("5009.*.1")"#, .active)
     assertIfConfig(#"_compiler_version("5009.*.3.2.3")"#, .unparsed)
     assertIfConfig(#"_compiler_version("5010.*.0")"#, .unparsed)
+    assertIfConfig("_compiler_version(>=5.8)", .active)
+    assertIfConfig("_compiler_version(>=12.0)", .unparsed)
     assertIfConfig("compiler(>=5.10) && 3.14159", .unparsed)
     assertIfConfig(
       "compiler(>=5.10) || 3.14159",
@@ -206,6 +219,17 @@ public class EvaluateTests: XCTestCase {
         )
       ]
     )
+    assertIfConfig(
+      #"_compiler_version("...")"#,
+      .unparsed,
+      diagnostics: [
+        DiagnosticSpec(
+          message: "found empty version component",
+          line: 1,
+          column: 20
+        )
+      ]
+    )
   }
 
   func testCanImport() throws {
@@ -269,7 +293,7 @@ fileprivate func assertIfConfig(
   // Evaluate the condition to check the state.
   let actualDiagnostics: [Diagnostic]
   let actualState: IfConfigRegionState
-  (actualState, actualDiagnostics) = IfConfigRegionState.evaluating(condition, in: configuration)
+  (actualState, _, actualDiagnostics) = IfConfigRegionState.evaluating(condition, in: configuration)
   XCTAssertEqual(actualState, expectedState, file: file, line: line)
 
   // Check the diagnostics.