Recognize ImpureFunction only under -Ycc

Author: odersky

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

@@ -199,7 +199,7 @@ object NameOps {
           else collectDigits(acc * 10 + d, idx + 1)
       collectDigits(0, suffixStart + 8)
 
-    private def isFunctionPrefix(suffixStart: Int, mustHave: String = ""): Boolean =
+    private def isFunctionPrefix(suffixStart: Int, mustHave: String = "")(using Context): Boolean =
       suffixStart >= 0
       && {
         val first = name.firstPart
@@ -209,47 +209,49 @@ object NameOps {
             if str == mustHave then found = true
             idx + str.length
           else idx
-        skip(skip(skip(0, "Impure"), "Erased"), "Context") == suffixStart
+        val start = if ctx.settings.Ycc.value then skip(0, "Impure") else 0
+        skip(skip(start, "Erased"), "Context") == suffixStart
         && found
       }
 
     /** Same as `funArity`, except that it returns -1 if the prefix
-     *  is not one of "", "Context", "Erased", "ErasedContext"
+     *  is not one of a (possibly empty) concatenation of a subset of
+     *  "Impure" (only under -Ycc), "Erased" and "Context" (in that order).
      */
-    private def checkedFunArity(suffixStart: Int): Int =
+    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
      */
-    def isFunction: Boolean =
+    def isFunction(using Context): Boolean =
       (name eq tpnme.FunctionXXL) || checkedFunArity(functionSuffixStart) >= 0
 
     /** Is a function name
      *    - FunctionN for N >= 0
      */
-    def isPlainFunction: Boolean = functionArity >= 0
+    def isPlainFunction(using Context): Boolean = functionArity >= 0
 
     /** Is a function name that contains `mustHave` as a substring */
-    private def isSpecificFunction(mustHave: String): Boolean =
+    private def isSpecificFunction(mustHave: String)(using Context): Boolean =
       val suffixStart = functionSuffixStart
       isFunctionPrefix(suffixStart, mustHave) && funArity(suffixStart) >= 0
 
-    def isContextFunction: Boolean = isSpecificFunction("Context")
-    def isErasedFunction: Boolean = isSpecificFunction("Erased")
-    def isImpureFunction: Boolean = isSpecificFunction("Impure")
+    def isContextFunction(using Context): Boolean = isSpecificFunction("Context")
+    def isErasedFunction(using Context): Boolean = isSpecificFunction("Erased")
+    def isImpureFunction(using Context): Boolean = isSpecificFunction("Impure")
 
     /** 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: Boolean =
+    def isSyntheticFunction(using Context): Boolean =
       val suffixStart = functionSuffixStart
       if suffixStart == 0 then funArity(suffixStart) > MaxImplementedFunctionArity
       else checkedFunArity(suffixStart) >= 0
 
-    def functionArity: Int =
+    def functionArity(using Context): Int =
       val suffixStart = functionSuffixStart
       if suffixStart >= 0 then checkedFunArity(suffixStart) else -1
 

tests/neg/cc-only-defs.scala

@@ -5,7 +5,7 @@ trait Test {
 
   val z: *.type // error
 
-  val b: ImpureFuntion1[Int, Int] // error
+  val b: ImpureFunction1[Int, Int] // error
 
   val a: {z} String // error
 }  // error