Add comments for isFunctionType-like functions

Author: natsukagami

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -1483,7 +1483,6 @@ class Definitions {
 
   /** Is any function class where
    *   - FunctionXXL
-   *   - ErasedFunction
    *   - FunctionN for N >= 0
    *   - ContextFunctionN for N >= 0
    */
@@ -1675,14 +1674,23 @@ class Definitions {
         skipRefined = false)
   end isNonRefinedFunction
 
-  /** Is `tp` a representation of a (possibly dependent) function type or an alias of such? */
+  /** Returns whether `tp` is an instance or a refined instance of:
+   *  - scala.FunctionN
+   *  - scala.ContextFunctionN
+   */
   def isFunctionType(tp: Type)(using Context): Boolean =
     isNonRefinedFunction(tp.dropDependentRefinement)
 
   /** Is `tp` a specialized, refined function type? Either an `ErasedFunction` or a `PolyFunction`. */
   def isRefinedFunctionType(tp: Type)(using Context): Boolean =
     (tp.typeSymbol eq defn.PolyFunctionClass) || isErasedFunctionType(tp)
 
+  /** Returns whether `tp` is an instance or a refined instance of:
+   *  - scala.FunctionN
+   *  - scala.ContextFunctionN
+   *  - ErasedFunction
+   *  - PolyFunction
+   */
   def isFunctionOrPolyType(tp: Type)(using Context): Boolean =
     isFunctionType(tp) || isRefinedFunctionType(tp)
 

compiler/src/dotty/tools/dotc/core/NameOps.scala

@@ -225,11 +225,10 @@ object NameOps {
     private def checkedFunArity(suffixStart: Int)(using Context): Int =
       if isFunctionPrefix(suffixStart) then funArity(suffixStart) else -1
 
-    /** Is a function name, i.e one of FunctionXXL, FunctionN, ContextFunctionN, ErasedFunctionN, ErasedContextFunctionN for N >= 0
+    /** Is a function name, i.e one of FunctionXXL, FunctionN, ContextFunctionN, ImpureFunctionN, ImpureContextFunctionN for N >= 0
      */
     def isFunction(using Context): Boolean =
       (name eq tpnme.FunctionXXL)
-      || (name eq tpnme.ErasedFunction)
       || checkedFunArity(functionSuffixStart) >= 0
 
     /** Is a function name
@@ -248,8 +247,6 @@ object NameOps {
     /** Is a synthetic function name, i.e. one of
      *    - FunctionN for N > 22
      *    - ContextFunctionN for N >= 0
-     *    - ErasedFunctionN for N >= 0
-     *    - ErasedContextFunctionN for N >= 0
      */
     def isSyntheticFunction(using Context): Boolean =
       val suffixStart = functionSuffixStart