Use isValidSwiftIdentifier(), add more tests

Author: grynspan

Sources/TestingMacros/Support/Additions/TokenSyntaxAdditions.swift

@@ -34,7 +34,7 @@ extension TokenSyntax {
   /// token, or `nil` if it does not represent one.
   var rawIdentifier: String? {
     let (textWithoutBackticks, backticksRemoved) = _textWithoutBackticks
-    if backticksRemoved, textWithoutBackticks.contains(where: \.isWhitespace) {
+    if backticksRemoved, !textWithoutBackticks.isValidSwiftIdentifier(for: .memberAccess) {
       return textWithoutBackticks
     }
 

Tests/TestingMacrosTests/TestDeclarationMacroTests.swift

@@ -256,6 +256,21 @@ struct TestDeclarationMacroTests {
     }
   }
 
+  @Test("Raw identifier is detected")
+  func rawIdentifier() {
+    #expect(TokenSyntax.identifier("`hello`").rawIdentifier == nil)
+    #expect(TokenSyntax.identifier("`helloworld`").rawIdentifier == nil)
+    #expect(TokenSyntax.identifier("`hélloworld`").rawIdentifier == nil)
+    #expect(TokenSyntax.identifier("`hello_world`").rawIdentifier == nil)
+    #expect(TokenSyntax.identifier("`hello world`").rawIdentifier != nil)
+    #expect(TokenSyntax.identifier("`hello/world`").rawIdentifier != nil)
+    #expect(TokenSyntax.identifier("`hello\tworld`").rawIdentifier != nil)
+
+    #expect(TokenSyntax.identifier("`class`").rawIdentifier == nil)
+    #expect(TokenSyntax.identifier("`struct`").rawIdentifier == nil)
+    #expect(TokenSyntax.identifier("`class struct`").rawIdentifier != nil)
+  }
+
   @Test("Warning diagnostics emitted on API misuse",
     arguments: [
       // return types