[PreCheck] Remove closure parameter validation

This is no longer necessary since parameter type would be validated
during constraint generation.

Author: xedin

lib/Sema/PreCheckExpr.cpp

@@ -1391,22 +1391,6 @@ namespace {
 /// Perform prechecking of a ClosureExpr before we dive into it.  This returns
 /// true when we want the body to be considered part of this larger expression.
 bool PreCheckExpression::walkToClosureExprPre(ClosureExpr *closure) {
-  auto *PL = closure->getParameters();
-
-  // Validate the parameters.
-  bool hadParameterError = false;
-
-  // If we encounter an error validating the parameter list, don't bail.
-  // Instead, go on to validate any potential result type, and bail
-  // afterwards.  This allows for better diagnostics, and keeps the
-  // closure expression type well-formed.
-  for (auto param : *PL) {
-    hadParameterError |= param->isInvalid();
-  }
-
-  if (hadParameterError)
-    return false;
-
   // If we won't be checking the body of the closure, don't walk into it here.
   if (!shouldTypeCheckInEnclosingExpression(closure))
     return false;

test/Constraints/tuple_arguments.swift

@@ -1468,11 +1468,11 @@ let _ = sr4745.enumerated().map { (count, element) in "\(count): \(element)" }
 // SR-4738
 
 let sr4738 = (1, (2, 3))
-[sr4738].map { (x, (y, z)) -> Int in x + y + z }
+[sr4738].map { (x, (y, z)) -> Int in x + y + z } // expected-note 2 {{'x' declared here}}
 // expected-error@-1 {{closure tuple parameter does not support destructuring}} {{20-26=arg1}} {{38-38=let (y, z) = arg1; }}
 // expected-warning@-2 {{unnamed parameters must be written with the empty name '_'}} {{20-20=_: }}
-// expected-error@-3 {{cannot find type 'y' in scope}}
-// expected-error@-4 {{cannot find type 'z' in scope}}
+// expected-error@-3 {{cannot find 'y' in scope; did you mean 'x'?}}
+// expected-error@-4 {{cannot find 'z' in scope; did you mean 'x'?}}
 
 // rdar://problem/31892961
 let r31892961_1 = [1: 1, 2: 2]
@@ -1482,9 +1482,8 @@ let r31892961_2 = [1, 2, 3]
 let _: [Int] = r31892961_2.enumerated().map { ((index, val)) in
   // expected-error@-1 {{closure tuple parameter does not support destructuring}} {{48-60=arg0}} {{3-3=\n  let (index, val) = arg0\n  }}
   // expected-warning@-2 {{unnamed parameters must be written with the empty name '_'}} {{48-48=_: }}
-  // expected-error@-3 {{cannot find type 'index' in scope}}
-  // expected-error@-4 {{cannot find type 'val' in scope}}
   val + 1
+  // expected-error@-1 {{cannot find 'val' in scope}}
 }
 
 let r31892961_3 = (x: 1, y: 42)
@@ -1695,7 +1694,7 @@ class Mappable<T> {
 }
 
 let x = Mappable(())
-// expected-note@-1 2{{'x' declared here}}
+// expected-note@-1 4{{'x' declared here}}
 x.map { (_: Void) in return () }
 x.map { (_: ()) in () }