Address pull request feedback

1. Tighten up the if else to avoid duplication
2. Add doc comments

src/compiler/scala/tools/reflect/quasiquotes/Reifiers.scala

@@ -218,10 +218,8 @@ trait Reifiers { self: Quasiquotes =>
       case Select(id @ Ident(nme.scala_), name) if id.symbol == ScalaPackage =>
         reifyBuildCall(nme.ScalaDot, name)
       case Select(qual, name) =>
-        if (name.isTypeName)
-          reifyBuildCall(nme.SyntacticSelectType, qual, name)
-        else
-          reifyBuildCall(nme.SyntacticSelectTerm, qual, name)
+        val ctor = if (name.isTypeName) nme.SyntacticSelectType else nme.SyntacticSelectTerm
+        reifyBuildCall(ctor, qual, name)
       case _ =>
         super.reifyTreeSyntactically(tree)
     }

src/reflect/scala/reflect/internal/ReificationSupport.scala

@@ -201,6 +201,9 @@ trait ReificationSupport { self: SymbolTable =>
       def unapply(flags: Long): Some[Long] = Some(flags)
     }
 
+    /** Construct/deconstruct type application term trees.
+     *  Treats other term trees as zero-argument type applications.
+     */
     object SyntacticTypeApplied extends SyntacticTypeAppliedExtractor {
       def apply(tree: Tree, targs: List[Tree]): Tree =
         if (targs.isEmpty) tree
@@ -214,6 +217,9 @@ trait ReificationSupport { self: SymbolTable =>
       }
     }
 
+    /** Construct/deconstruct applied type trees.
+     *  Treats other types as zero-arity applied types.
+     */
     object SyntacticAppliedType extends SyntacticTypeAppliedExtractor {
       def apply(tree: Tree, targs: List[Tree]): Tree =
         if (targs.isEmpty) tree
@@ -235,10 +241,10 @@ trait ReificationSupport { self: SymbolTable =>
         case UnApply(treeInfo.Unapplied(Select(fun, nme.unapply)), pats) =>
           Some((fun, pats :: Nil))
         case treeInfo.Applied(fun, targs, argss) =>
-          if (fun.isTerm)
-            Some((SyntacticTypeApplied(fun, targs), argss))
-          else
-            Some((SyntacticAppliedType(fun, targs), argss))
+          val callee =
+            if (fun.isTerm) SyntacticTypeApplied(fun, targs)
+            else SyntacticAppliedType(fun, targs)
+          Some((callee, argss))
       }
     }