[Property wrappers] Avoid assign_by_wrapper when autoclosure is involved

When assigning to a wrapped variable in 'init()', if the property wrapper's
'wrappedValue:' parameter is an escaping autoclosure, the initializer and
setter have incompatible types -- the setter takes a value, and initializer
takes a closure returning that value.

An assign_by_wrapper with incompatible types causes SIL verification to fail.

This commit makes the SIL not use assign_by_wrapper in such cases, and use the
setter directly, resulting in a definitive initialization (DI) error instead.

    struct S {
      @lazy var n: Int // Lazy.init(wrappedValue: @autoclosure ... )
      init() {
        n = 1 // error: 'self' used before all stored properties are initialized
      }
    }

Author: roop

lib/SILGen/SILGenLValue.cpp

@@ -1321,6 +1321,13 @@ namespace {
           return false;
         }
 
+        // If this property wrapper uses autoclosure in it's initializer,
+        // the argument types of the setter and initializer shall be
+        // different, so we don't rewrite an assignment into an
+        // initialization.
+        if (VD->isInnermostPropertyWrapperInitUsesEscapingAutoClosure())
+          return false;
+
         return true;
       }