Add assertion for missing fixed source

Tests/SwiftParserTest/Assertions.swift

@@ -604,7 +604,9 @@ func assertParse<S: SyntaxProtocol>(
   }
 
   // Applying Fix-Its
-  if let expectedFixedSource = expectedFixedSource {
+  if expectedDiagnostics.contains(where: { !$0.fixIts.isEmpty }) && expectedFixedSource == nil {
+    XCTFail("Expected a fixed source if the test case produces diagnostics with Fix-Its", file: file, line: line)
+  } else if let expectedFixedSource = expectedFixedSource {
     let fixedTree = FixItApplier.applyFixes(in: diags, withMessages: applyFixIts, to: tree)
     var fixedTreeDescription = fixedTree.description
     if options.contains(.normalizeNewlinesInFixedSource) {
@@ -621,6 +623,10 @@ func assertParse<S: SyntaxProtocol>(
     )
   }
 
+  if expectedDiagnostics.allSatisfy({ $0.fixIts.isEmpty }) && expectedFixedSource != nil {
+    XCTFail("A fixed source was provided but the test case produces no diagnostics with Fix-Its", file: file, line: line)
+  }
+
   if expectedDiagnostics.isEmpty {
     assertBasicFormat(source: source, parse: parse, file: file, line: line)
   }

Tests/SwiftParserTest/AttributeTests.swift

@@ -63,7 +63,10 @@ final class AttributeTests: XCTestCase {
         DiagnosticSpec(message: "expected ':' in attribute argument", fixIts: ["insert ':'"]),
         DiagnosticSpec(message: "expected ')' to end attribute", fixIts: ["insert ')'"]),
         DiagnosticSpec(message: "expected declaration after attribute", fixIts: ["insert declaration"]),
-      ]
+      ],
+      fixedSource: """
+        @_specialize(e:) <#declaration#>
+        """
     )
   }
 
@@ -76,7 +79,10 @@ final class AttributeTests: XCTestCase {
         DiagnosticSpec(locationMarker: "1️⃣", message: "expected ':' in attribute argument", fixIts: ["insert ':'"]),
         DiagnosticSpec(locationMarker: "2️⃣", message: "expected ': false' in attribute argument", fixIts: ["insert ': false'"]),
         DiagnosticSpec(locationMarker: "3️⃣", message: "expected declaration after attribute", fixIts: ["insert declaration"]),
-      ]
+      ],
+      fixedSource: """
+        @_specialize(e:, exported: false)  <#declaration#>
+        """
     )
   }
 
@@ -502,7 +508,11 @@ final class AttributeTests: XCTestCase {
       diagnostics: [
         DiagnosticSpec(message: "expected ':' and string literal in @_unavailableFromAsync argument", fixIts: ["insert ':' and string literal"]),
         DiagnosticSpec(message: #"unexpected code '= "abc"' in attribute"#),
-      ]
+      ],
+      fixedSource: """
+        @_unavailableFromAsync(message: ""= "abc")
+        func foo() {}
+        """
     )
 
     assertParse(

Tests/SwiftParserTest/AvailabilityTests.swift

@@ -151,7 +151,11 @@ final class AvailabilityTests: XCTestCase {
       diagnostics: [
         DiagnosticSpec(message: "expected version tuple in version restriction", fixIts: ["insert version tuple"]),
         DiagnosticSpec(message: "unexpected code '10e10' in attribute"),
-      ]
+      ],
+      fixedSource: """
+        @available(OSX <#integer literal#>10e10)
+        func test() {}
+        """
     )
 
     assertParse(
@@ -162,7 +166,11 @@ final class AvailabilityTests: XCTestCase {
       diagnostics: [
         DiagnosticSpec(message: "expected integer literal in version tuple", fixIts: ["insert integer literal"]),
         DiagnosticSpec(message: "unexpected code '0e10' in attribute"),
-      ]
+      ],
+      fixedSource: """
+        @available(OSX 10.<#integer literal#>0e10)
+        func test() {}
+        """
     )
 
     assertParse(
@@ -173,7 +181,11 @@ final class AvailabilityTests: XCTestCase {
       diagnostics: [
         DiagnosticSpec(message: "expected version tuple in version restriction", fixIts: ["insert version tuple"]),
         DiagnosticSpec(message: "unexpected code '0xff' in attribute"),
-      ]
+      ],
+      fixedSource: """
+        @available(OSX <#integer literal#>0xff)
+        func test() {}
+        """
     )
 
     assertParse(
@@ -184,8 +196,11 @@ final class AvailabilityTests: XCTestCase {
       diagnostics: [
         DiagnosticSpec(message: "expected integer literal in version tuple", fixIts: ["insert integer literal"]),
         DiagnosticSpec(message: "unexpected code '0xff' in attribute"),
-      ]
+      ],
+      fixedSource: """
+        @available(OSX 1.0.<#integer literal#>0xff)
+        func test() {}
+        """
     )
-
   }
 }