[AST] Properly initialize FunctionRefKind for UnresolvedMemberExpr

Author: Jumhyn

include/swift/AST/Expr.h

@@ -1841,7 +1841,21 @@ class UnresolvedMemberExpr final
   UnresolvedMemberExpr(SourceLoc dotLoc, DeclNameLoc nameLoc, DeclNameRef name,
                        bool implicit)
     : Expr(ExprKind::UnresolvedMember, implicit), DotLoc(dotLoc),
-      NameLoc(nameLoc), Name(name) {}
+      NameLoc(nameLoc), Name(name) {
+    // FIXME: Really, we should be setting this to `FunctionRefKind::Compound`
+    // if `NameLoc` is compound, but this would be a source break for cases like
+    // ```
+    // struct S {
+    //   static func makeS(_: Int) -> S! { S() }
+    // }
+    //
+    // let s: S = .makeS(_:)(0)
+    // ```
+    // Instead, we should store compound-ness as a separate bit from applied/
+    // unapplied.
+    Bits.UnresolvedMemberExpr.FunctionRefKind =
+        static_cast<unsigned>(FunctionRefKind::Unapplied);
+  }
 
   DeclNameRef getName() const { return Name; }
   DeclNameLoc getNameLoc() const { return NameLoc; }