Merge pull request swiftlang#33590 from xedin/fail-on-error-if-single-stmt

[CSGen] Abort constraint generation on error only if closure part…

Author: xedin

lib/Sema/CSGen.cpp

@@ -2775,10 +2775,17 @@ namespace {
           return { true, expr };
         }
       } collectVarRefs(CS);
+
       closure->walk(collectVarRefs);
 
-      if (collectVarRefs.hasErrorExprs)
+      // If walker discovered error expressions, let's fail constraint
+      // genreation only if closure is going to participate
+      // in the type-check. This allows us to delay validation of
+      // multi-statement closures until body is opened.
+      if (shouldTypeCheckInEnclosingExpression(closure) &&
+          collectVarRefs.hasErrorExprs) {
         return Type();
+      }
 
       auto inferredType = inferClosureType(closure);
       if (!inferredType || inferredType->hasError())

test/expr/closure/closures.swift

@@ -141,6 +141,7 @@ func anonymousClosureArgsInClosureWithArgs() {
   var a5 = { (_: [Int], w: [Int]) in
     f($0.count) // expected-error {{anonymous closure arguments cannot be used inside a closure that has explicit arguments}}
     f($1.count) // expected-error {{anonymous closure arguments cannot be used inside a closure that has explicit arguments; did you mean 'w'?}} {{7-9=w}}
+    // expected-error@-1 {{cannot convert value of type 'Int' to expected argument type 'String'}}
   }
 }