Update tests to use the new visitor pattern

Author: nkcsgexi

Tests/SwiftSyntaxTest/AbsolutePosition.swift

@@ -69,7 +69,7 @@ public class AbsolutePositionTestCase: XCTestCase {
             node.position.utf8Offset + node.leadingTrivia.byteSize)
         }
       }
-      Visitor().visit(parsed)
+      parsed.walk(Visitor())
     }())
   }
 

Tests/SwiftSyntaxTest/DiagnosticTest.swift

@@ -76,19 +76,20 @@ public class DiagnosticTestCase: XCTestCase {
         self.url = url
         self.engine = engine
       }
-      override func visit(_ function: FunctionDeclSyntax) {
+      override func visit(_ function: FunctionDeclSyntax) -> Bool {
         let startLoc = function.identifier.startLocation(in: url)
         let endLoc = function.endLocation(in: url)
         engine.diagnose(.badFunction(function.identifier), location: startLoc) {
           $0.highlight(function.identifier.sourceRange(in: self.url))
         }
         engine.diagnose(.endOfFunction(function.identifier), location: endLoc)
+        return true
       }
     }
 
     XCTAssertNoThrow(try {
       let file = try SyntaxTreeParser.parse(url)
-       Visitor(url: url, engine: engine).visit(file)
+       file.walk(Visitor(url: url, engine: engine))
     }())
 
      XCTAssertEqual(6, engine.diagnostics.count)

Tests/SwiftSyntaxTest/VisitorTest.swift

@@ -13,16 +13,16 @@ public class SyntaxVisitorTestCase: XCTestCase {
   public func testBasic() {
     class FuncCounter: SyntaxVisitor {
       var funcCount = 0
-      override func visit(_ node: FunctionDeclSyntax) {
+      override func visit(_ node: FunctionDeclSyntax) -> Bool {
         funcCount += 1
-        super.visit(node)
+        return true
       }
     }
     XCTAssertNoThrow(try {
       let parsed = try SyntaxTreeParser.parse(getInput("visitor.swift"))
       let counter = FuncCounter()
       let hashBefore = parsed.hashValue
-      counter.visit(parsed)
+      parsed.walk(counter)
       XCTAssertEqual(counter.funcCount, 3)
       XCTAssertEqual(hashBefore, parsed.hashValue)
     }())
@@ -70,16 +70,16 @@ public class SyntaxVisitorTestCase: XCTestCase {
     class VisitCollections: SyntaxVisitor {
       var numberOfCodeBlockItems = 0
 
-      override func visit(_ items: CodeBlockItemListSyntax) {
+      override func visit(_ items: CodeBlockItemListSyntax) -> Bool {
         numberOfCodeBlockItems += items.count
-        super.visit(items)
+        return true
       }
     }
 
     XCTAssertNoThrow(try {
       let parsed = try SyntaxTreeParser.parse(getInput("nested-blocks.swift"))
       let visitor = VisitCollections()
-      visitor.visit(parsed)
+      parsed.walk(visitor)
       XCTAssertEqual(4, visitor.numberOfCodeBlockItems)
     }())
   }