[SR-1752] Fix warning about unused result if return type is Void?

Author: ahoppen

lib/Sema/TypeCheckStmt.cpp

@@ -1041,9 +1041,9 @@ void TypeChecker::checkIgnoredExpr(Expr *E) {
     return;
   }
 
-  // If the result of this expression is of type "()", then it is safe to
-  // ignore.
-  if (valueE->getType()->isVoid() ||
+  // If the result of this expression is of type "()" potentially wrapped in
+  // optionals, then it is safe to ignore.
+  if (valueE->getType()->lookThroughAllAnyOptionalTypes()->isVoid() ||
       valueE->getType()->is<ErrorType>())
     return;
 

test/Constraints/diagnostics.swift

@@ -822,3 +822,12 @@ func rdar24202058(a : Int) {
   return a <= 480 // expected-error {{'<=' produces 'Bool', not the expected contextual result type '()'}}
 }
 
+// SR-1752: Warning about unused result with ternary operator
+
+struct SR1752 {
+  func foo() {}
+}
+
+let sr1752: SR1752? = nil
+
+true ? nil : sr1752?.foo() // don't generate a warning about unused result since foo returns Void

test/Parse/try.swift

@@ -110,11 +110,11 @@ let _: String = doubleOptional // expected-error {{cannot convert value of type
 func maybeThrow() throws {}
 try maybeThrow() // okay
 try! maybeThrow() // okay
-try? maybeThrow() // expected-warning {{result of 'try?' is unused}}
+try? maybeThrow() // okay since return type of maybeThrow is Void
 _ = try? maybeThrow() // okay
 
 let _: () -> Void = { try! maybeThrow() } // okay
-let _: () -> Void = { try? maybeThrow() } // expected-warning {{result of 'try?' is unused}}
+let _: () -> Void = { try? maybeThrow() } // okay since return type of maybeThrow is Void
 
 
 if try? maybeThrow() { // expected-error {{cannot be used as a boolean}} {{4-4=((}} {{21-21=) != nil)}}