Backport "Fix implicitNotFound message for type aliases" (#20275)

Backports #19343 to 3.3

Fix #7092

Author: WojciechMazur

compiler/src/dotty/tools/dotc/reporting/messages.scala

@@ -2796,19 +2796,27 @@ class MissingImplicitArgument(
       val idx = paramNames.indexOf(name)
       if (idx >= 0) Some(i"${args(idx)}") else None
     """\$\{\s*([^}\s]+)\s*\}""".r.replaceAllIn(raw, (_: Regex.Match) match
-      case Regex.Groups(v) => quoteReplacement(translate(v).getOrElse("")).nn
+      case Regex.Groups(v) => quoteReplacement(translate(v).getOrElse("?" + v)).nn
     )
 
   /** @param rawMsg           Message template with variables, e.g. "Variable A is ${A}"
    *  @param sym              Symbol of the annotated type or of the method whose parameter was annotated
+   *  @param paramNames       Names of type parameters to substitute with `args` in the message template
+   *  @param args             Resolved type arguments to substitute for `paramNames` in the message template
    *  @param substituteType   Function substituting specific types for abstract types associated with variables, e.g A -> Int
    */
-  def formatAnnotationMessage(rawMsg: String, sym: Symbol, substituteType: Type => Type)(using Context): String =
+  def formatAnnotationMessage(
+    rawMsg: String,
+    sym: Symbol,
+    paramNames: List[Name],
+    args: List[Type],
+    substituteType: Type => Type,
+  )(using Context): String =
     val substitutableTypesSymbols = substitutableTypeSymbolsInScope(sym)
     userDefinedErrorString(
       rawMsg,
-      paramNames = substitutableTypesSymbols.map(_.name.unexpandedName.toString),
-      args = substitutableTypesSymbols.map(_.typeRef).map(substituteType)
+      paramNames = (paramNames ::: substitutableTypesSymbols.map(_.name)).map(_.unexpandedName.toString),
+      args = args ::: substitutableTypesSymbols.map(_.typeRef).map(substituteType)
     )
 
   /** Extract a user defined error message from a symbol `sym`
@@ -2820,14 +2828,17 @@ class MissingImplicitArgument(
       msg <- ann.argumentConstantString(0)
     yield msg
 
-  def userDefinedImplicitNotFoundTypeMessageFor(sym: Symbol)(using Context): Option[String] =
-    for
-      rawMsg <- userDefinedMsg(sym, defn.ImplicitNotFoundAnnot)
-      if Feature.migrateTo3 || sym != defn.Function1
-        // Don't inherit "No implicit view available..." message if subtypes of Function1 are not treated as implicit conversions anymore
-    yield
-      val substituteType = (_: Type).asSeenFrom(pt, sym)
-      formatAnnotationMessage(rawMsg, sym, substituteType)
+  def userDefinedImplicitNotFoundTypeMessageFor(
+    sym: Symbol,
+    params: List[ParamInfo] = Nil,
+    args: List[Type] = Nil
+  )(using Context): Option[String] = for
+    rawMsg <- userDefinedMsg(sym, defn.ImplicitNotFoundAnnot)
+    if Feature.migrateTo3 || sym != defn.Function1
+    // Don't inherit "No implicit view available..." message if subtypes of Function1 are not treated as implicit conversions anymore
+  yield
+    val paramNames = params.map(_.paramName)
+    formatAnnotationMessage(rawMsg, sym, paramNames, args, _.asSeenFrom(pt, sym))
 
   /** Extracting the message from a method parameter, e.g. in
    *
@@ -2842,19 +2853,22 @@ class MissingImplicitArgument(
         val targs = tpd.typeArgss(applTree).flatten
         val methodOwner = fn.symbol.owner
         val methodOwnerType = tpd.qualifier(fn).tpe
-        val methodTypeParams = fn.symbol.paramSymss.flatten.filter(_.isType)
+        val methodTypeParams = fn.symbol.paramSymss.flatten.withFilter(_.isType).map(_.name)
         val methodTypeArgs = targs.map(_.tpe)
-        val substituteType = (_: Type).asSeenFrom(methodOwnerType, methodOwner).subst(methodTypeParams, methodTypeArgs)
-        formatAnnotationMessage(rawMsg, sym.owner, substituteType)
+        formatAnnotationMessage(rawMsg, sym.owner, methodTypeParams, methodTypeArgs, _.asSeenFrom(methodOwnerType, methodOwner))
 
   def userDefinedImplicitNotFoundTypeMessage(using Context): Option[String] =
-    def recur(tp: Type): Option[String] = tp match
+    def recur(tp: Type, params: List[ParamInfo] = Nil, args: List[Type] = Nil): Option[String] = tp match
+      case tp: AppliedType =>
+        val tycon = tp.typeConstructor
+        val typeParams = if tycon.isLambdaSub then tycon.hkTypeParams else tycon.typeParams
+        recur(tycon, typeParams ::: params, tp.args ::: args)
       case tp: TypeRef =>
-        val sym = tp.symbol
-        userDefinedImplicitNotFoundTypeMessageFor(sym).orElse(recur(tp.info))
+        userDefinedImplicitNotFoundTypeMessageFor(tp.symbol, params, args)
+          .orElse(recur(tp.info))
       case tp: ClassInfo =>
         tp.baseClasses.iterator
-          .map(userDefinedImplicitNotFoundTypeMessageFor)
+          .map(userDefinedImplicitNotFoundTypeMessageFor(_))
           .find(_.isDefined).flatten
       case tp: TypeProxy =>
         recur(tp.superType)

compiler/test/dotty/tools/vulpix/ParallelTesting.scala

@@ -266,12 +266,11 @@ trait ParallelTesting extends RunnerOrchestration { self =>
      */
     final def diffTest(testSource: TestSource, checkFile: JFile, actual: List[String], reporters: Seq[TestReporter], logger: LoggedRunnable) = {
       for (msg <- FileDiff.check(testSource.title, actual, checkFile.getPath)) {
-        onFailure(testSource, reporters, logger, Some(msg))
-
         if (updateCheckFiles) {
           FileDiff.dump(checkFile.toPath.toString, actual)
           echo("Updated checkfile: " + checkFile.getPath)
         } else {
+          onFailure(testSource, reporters, logger, Some(msg))
           val outFile = checkFile.toPath.resolveSibling(s"${checkFile.toPath.getFileName}.out").toString
           FileDiff.dump(outFile, actual)
           echo(FileDiff.diffMessage(checkFile.getPath, outFile))

tests/neg/i4986c.check

@@ -61,4 +61,4 @@
 -- [E172] Type Error: tests/neg/i4986c.scala:62:19 ---------------------------------------------------------------------
 62 |  i.m[Option[Long]] // error
    |                   ^
-   |                   String; List; [A, _] =>> List[Option[?]]; Int; Option[Long]; 
+   |                   String; List; [A, _] =>> List[Option[?]]; Int; Option[Long]; ?XX

tests/neg/i7092.check

@@ -0,0 +1,32 @@
+-- [E172] Type Error: tests/neg/i7092.scala:24:19 ----------------------------------------------------------------------
+24 |  summon[F[String]] // error
+   |                   ^
+   |                   Not found for String
+-- [E172] Type Error: tests/neg/i7092.scala:25:19 ----------------------------------------------------------------------
+25 |  summon[G[String]] // error
+   |                   ^
+   |                   Not found for String
+-- [E172] Type Error: tests/neg/i7092.scala:26:16 ----------------------------------------------------------------------
+26 |  summon[H[Int]] // error
+   |                ^
+   |                Not found for Int, ?B
+-- [E172] Type Error: tests/neg/i7092.scala:27:23 ----------------------------------------------------------------------
+27 |  summon[H[Int][Float]] // error
+   |                       ^
+   |                       Not found for Int, Float
+-- [E172] Type Error: tests/neg/i7092.scala:28:18 ----------------------------------------------------------------------
+28 |  summon[AAA[Int]] // error
+   |                  ^
+   |                  Not found for Int
+-- [E172] Type Error: tests/neg/i7092.scala:29:25 ----------------------------------------------------------------------
+29 |  summon[AAA[Int][Float]] // error
+   |                         ^
+   |                         Not found for Int
+-- [E172] Type Error: tests/neg/i7092.scala:30:19 ----------------------------------------------------------------------
+30 |  summon[op.F[Int]] // error
+   |                   ^
+   |                   Could not find Int
+-- [E172] Type Error: tests/neg/i7092.scala:31:28 ----------------------------------------------------------------------
+31 |  summon[String =!:= String] // error
+   |                            ^
+   |                            Cannot proof type inequality because types are equal: String =:= String

tests/neg/i7092.scala

@@ -0,0 +1,31 @@
+import scala.annotation.implicitNotFound
+import scala.util.NotGiven
+
+@implicitNotFound("Not found for ${A}")
+type F[A]
+
+@implicitNotFound("Not found for ${A}")
+trait G[A]
+
+@implicitNotFound("Not found for ${A}, ${B}")
+type H = [A] =>> [B] =>> (A, B)
+
+@implicitNotFound("Not found for ${A}")
+type AAA = [A] =>> [A] =>> A
+
+object op:
+  @implicitNotFound("Could not find ${A}")
+  opaque type F[A] = A
+
+@implicitNotFound("Cannot proof type inequality because types are equal: ${A} =:= ${B}")
+type =!:=[A, B] = NotGiven[A =:= B]
+
+object Test:
+  summon[F[String]] // error
+  summon[G[String]] // error
+  summon[H[Int]] // error
+  summon[H[Int][Float]] // error
+  summon[AAA[Int]] // error
+  summon[AAA[Int][Float]] // error
+  summon[op.F[Int]] // error
+  summon[String =!:= String] // error