Fix Fix-It location for "unsafe" when calling an initializer

The implicit reference to the initializer was tripping up the logic
for finding the appropriate place to insert "unsafe", and it was ending
up in the middle of the expression.

Author: DougGregor

lib/Sema/TypeCheckEffects.cpp

@@ -3172,7 +3172,7 @@ class CheckEffectsCoverage : public EffectsHandlingWalker<CheckEffectsCoverage>
       return false;
 
     return isa<AbstractClosureExpr>(e) || isa<DiscardAssignmentExpr>(e) ||
-           isa<AssignExpr>(e) || (isa<DeclRefExpr>(e) && e->isImplicit());
+           isa<AssignExpr>(e);
   }
 
   static bool isAnchorTooEarly(Expr *e) {

test/Unsafe/unsafe.swift

@@ -123,6 +123,19 @@ class ExclusivityChecking {
 // TODO: diagnose the need for @unsafe when there's an unsafe superclass.
 class UnsafeSub: UnsafeSuper { }
 
+// -----------------------------------------------------------------------
+// Miscellaneous expression issues
+// -----------------------------------------------------------------------
+
+struct BufferThingy<T> {
+  @unsafe init(count: Int) { }
+}
+
+func testConstruction() {
+  let _ = BufferThingy<Int>(count: 17) // expected-warning{{expression uses unsafe constructs but is not marked with 'unsafe' [Unsafe]}}{{11-11=unsafe }}
+  // expected-note@-1{{reference to unsafe initializer 'init(count:)'}}
+}
+
 // -----------------------------------------------------------------------
 // Declaration references
 // -----------------------------------------------------------------------