[SR-4205] Removed the non_trailing_closure_before_default_args warning (#8033)

rdar://problem/21193574 says that this warning dates back to when closure args before default args used to be considered as trailing closures. This is not the case anymore so Jordan suggested we remove the warning.

Author: hartbit

include/swift/AST/DiagnosticsSema.def

@@ -1236,9 +1236,6 @@ WARNING(function_type_access_warn,none,
         "because its %select{parameter|result}5 uses "
         "%select{a private|a fileprivate|an internal|%error|%error}3 type",
         (bool, Accessibility, bool, Accessibility, unsigned, bool))
-WARNING(non_trailing_closure_before_default_args,none,
-        "closure parameter prior to parameters with default arguments will "
-        "not be treated as a trailing closure", ())
 ERROR(noreturn_not_supported,none,
       "'@noreturn' has been removed; functions that never return should have a "
       "return type of 'Never' instead", ())

lib/Sema/TypeCheckDecl.cpp

@@ -5041,43 +5041,6 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
         makeFinal(TC.Context, FD);
       }
     }
-
-    // Check whether we have parameters with default arguments that follow a
-    // closure parameter; warn about such things, because the closure will not
-    // be treated as a trailing closure.
-    if (!FD->isImplicit()) {
-      auto paramList = FD->getParameterList(FD->getImplicitSelfDecl() ? 1 : 0);
-      bool anyDefaultArguments = false;
-      for (unsigned i = paramList->size(); i != 0; --i) {
-        // Determine whether the parameter is of (possibly lvalue, possibly
-        // optional), non-autoclosure function type, which could receive a
-        // closure. We look at the type sugar directly, so that one can
-        // suppress this warning by adding parentheses.
-        auto &param = paramList->get(i-1);
-        auto paramType = param->getType();
-
-        if (auto *funcTy = isUnparenthesizedTrailingClosure(paramType)) {
-          // If we saw any default arguments before this, complain.
-          // This doesn't apply to autoclosures.
-          if (anyDefaultArguments && !funcTy->getExtInfo().isAutoClosure()) {
-            TC.diagnose(param->getStartLoc(),
-                        diag::non_trailing_closure_before_default_args)
-              .highlight(param->getSourceRange());
-          }
-
-          break;
-        }
-
-        // If we have a default argument, keep going.
-        if (param->isDefaultArgument()) {
-          anyDefaultArguments = true;
-          continue;
-        }
-
-        // We're done.
-        break;
-      }
-    }
   }
 
   void visitModuleDecl(ModuleDecl *) { }

test/attr/attr_noescape.swift

@@ -213,9 +213,7 @@ func r19763676Caller(_ g: @noescape (Int) -> Int) { // expected-warning{{@noesca
 
 
 // <rdar://problem/19763732> False positive in @noescape analysis triggered by default arguments
-func calleeWithDefaultParameters(_ f: @noescape () -> (), x : Int = 1) {}  // expected-warning {{closure parameter prior to parameters with default arguments will not be treated as a trailing closure}}
-  // expected-warning@-1{{@noescape is the default and is deprecated}} {{39-49=}}
-
+func calleeWithDefaultParameters(_ f: @noescape () -> (), x : Int = 1) {} // expected-warning{{@noescape is the default and is deprecated}} {{39-49=}}
 func callerOfDefaultParams(_ g: @noescape () -> ()) { // expected-warning{{@noescape is the default and is deprecated}} {{33-43=}}
   calleeWithDefaultParameters(g)
 }

test/decl/func/trailing_closures.swift

@@ -1,13 +1,5 @@
 // RUN: %target-typecheck-verify-swift
 
-// Warn about non-trailing closures followed by parameters with
+// SR-4205: Don't warn about non-trailing closures followed by parameters with
 // default arguments.
-func f1(_ f: () -> (), bar: Int = 10) { } // expected-warning{{closure parameter prior to parameters with default arguments will not be treated as a trailing closure}}
-func f2(_ f: (() -> ())!, bar: Int = 10, wibble: Int = 17) { } // expected-warning{{closure parameter prior to parameters with default arguments will not be treated as a trailing closure}}
-func f3(_ f: (() -> ())?, bar: Int = 10) { } // expected-warning{{closure parameter prior to parameters with default arguments will not be treated as a trailing closure}}
-
-// An extra set of parentheses suppresses the warning.
-func g1(_ f: (() -> ()), bar: Int = 10) { } // no-warning
-
-// Stop at the first closure.
-func g2(_ f: () -> (), g: (() -> ())? = nil) { } // no-warning
+func f1(_ f: () -> (), bar: Int = 10) { } // no-warning

test/expr/closure/closures.swift

@@ -3,7 +3,7 @@
 var func6 : (_ fn : (Int,Int) -> Int) -> ()
 var func6a : ((Int, Int) -> Int) -> ()
 var func6b : (Int, (Int, Int) -> Int) -> ()
-func func6c(_ f: (Int, Int) -> Int, _ n: Int = 0) {} // expected-warning{{prior to parameters}}
+func func6c(_ f: (Int, Int) -> Int, _ n: Int = 0) {}
 
 
 // Expressions can be auto-closurified, so that they can be evaluated separately