Merge pull request #418 from gregomni/sr-184

[SR-184] Better diagnose error via unwrapping optional before initialized.

Author: slavapestov

lib/SILPasses/EarlySIL/DefiniteInitialization.cpp

@@ -1094,6 +1094,8 @@ void LifetimeChecker::handleEscapeUse(const DIMemoryUse &Use) {
       DiagMessage = diag::variable_closure_use_uninit;
     else
       DiagMessage = diag::variable_function_use_uninit;
+  } else if (isa<UncheckedTakeEnumDataAddrInst>(Inst)) {
+    DiagMessage = diag::variable_used_before_initialized;
   } else {
     DiagMessage = diag::variable_closure_use_uninit;
   }

test/SILPasses/definite_init_diagnostics.swift

@@ -78,6 +78,12 @@ func test2() {
   takes_closure {     // ok.
     markUsed(b3)
   }
+    
+  var b4 : Int?
+  takes_closure {     // ok.
+    markUsed(b4!)
+  }
+  b4 = 7
 
   // Structs
   var s1 : SomeStruct
@@ -1184,3 +1190,9 @@ func test22436880() {
   x = 1
   bug22436880(&x) // expected-error {{immutable value 'x' may not be passed inout}}
 }
+
+// sr-184
+let x: String? // expected-note 2 {{constant defined here}}
+print(x?.characters.count) // expected-error {{constant 'x' used before being initialized}}
+print(x!) // expected-error {{constant 'x' used before being initialized}}
+