Correctly identify functions with trailing closures. (swiftlang#97)

Author: dabelknap

Sources/Rules/NoEmptyTrailingClosureParentheses.swift

@@ -15,7 +15,13 @@ public final class NoEmptyTrailingClosureParentheses: SyntaxFormatRule {
   public override func visit(_ node: FunctionCallExprSyntax) -> ExprSyntax {
     guard node.argumentList.count == 0 else { return node }
 
-    guard let name = node.calledExpression.firstToken?.withoutTrivia() else { return node }
+    guard node.trailingClosure != nil && node.argumentList.isEmpty && node.leftParen != nil else {
+        return node
+    }
+    guard let name = node.calledExpression.lastToken?.withoutTrivia() else {
+        return node
+    }
+
     diagnose(.removeEmptyTrailingParentheses(name: "\(name)"), on: node)
 
     let formattedExp = replaceTrivia(on: node.calledExpression,

Tests/SwiftFormatTests/NoEmptyTrailingClosureParenthesesTests.swift

@@ -17,6 +17,12 @@ public class NoEmptyTrailingClosureParenthesesTests: DiagnosingTestCase {
              }
              greetEnthusiastically() { "John" }
              greetApathetically { "not John" }
+             func myfunc(cls: MyClass) {
+               cls.myClosure { $0 }
+             }
+             func myfunc(cls: MyClass) {
+               cls.myBadClosure() { $0 }
+             }
              """,
       expected: """
                 func greetEnthusiastically(_ nameProvider: () -> String) {
@@ -27,8 +33,16 @@ public class NoEmptyTrailingClosureParenthesesTests: DiagnosingTestCase {
                 }
                 greetEnthusiastically { "John" }
                 greetApathetically { "not John" }
+                func myfunc(cls: MyClass) {
+                  cls.myClosure { $0 }
+                }
+                func myfunc(cls: MyClass) {
+                  cls.myBadClosure { $0 }
+                }
                 """)
     XCTAssertDiagnosed(.removeEmptyTrailingParentheses(name: "greetEnthusiastically"))
+    XCTAssertDiagnosed(.removeEmptyTrailingParentheses(name: "myBadClosure"))
+    XCTAssertNotDiagnosed(.removeEmptyTrailingParentheses(name: "myClosure"))
   }
 
   #if !os(macOS)