Fix ignored type variable bound warning in type quote pattern (#18199)

See the diff in tests/neg-macros/quote-type-variable-no-inference.check

Author: nicolasstucki

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -1014,7 +1014,7 @@ object desugar {
    *  if the type has a pattern variable name
    */
   def quotedPatternTypeDef(tree: TypeDef)(using Context): TypeDef = {
-    assert(ctx.mode.is(Mode.QuotedPattern))
+    assert(ctx.mode.isQuotedPattern)
     if tree.name.isVarPattern && !tree.isBackquoted then
       val patternTypeAnnot = New(ref(defn.QuotedRuntimePatterns_patternTypeAnnot.typeRef)).withSpan(tree.span)
       val mods = tree.mods.withAddedAnnotation(patternTypeAnnot)
@@ -1363,7 +1363,7 @@ object desugar {
       case tree: ValDef => valDef(tree)
       case tree: TypeDef =>
         if (tree.isClassDef) classDef(tree)
-        else if (ctx.mode.is(Mode.QuotedPattern)) quotedPatternTypeDef(tree)
+        else if (ctx.mode.isQuotedPattern) quotedPatternTypeDef(tree)
         else tree
       case tree: DefDef =>
         if (tree.name.isConstructorName) tree // was already handled by enclosing classDef

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

@@ -10,6 +10,9 @@ case class Mode(val bits: Int) extends AnyVal {
 
   def isExpr: Boolean = (this & PatternOrTypeBits) == None
 
+  /** Are we in the body of quoted pattern? */
+  def isQuotedPattern: Boolean = (this & QuotedPatternBits) != None
+
   override def toString: String =
     (0 until 31).filter(i => (bits & (1 << i)) != 0).map(modeName).mkString("Mode(", ",", ")")
 
@@ -69,6 +72,9 @@ object Mode {
    */
   val Printing: Mode = newMode(10, "Printing")
 
+  /** Are we in a quote the body of quoted type pattern? */
+  val QuotedTypePattern: Mode = newMode(11, "QuotedTypePattern")
+
   /** We are currently in a `viewExists` check. In that case, ambiguous
    *  implicits checks are disabled and we succeed with the first implicit
    *  found.
@@ -128,8 +134,10 @@ object Mode {
   /** Are we trying to find a hidden implicit? */
   val FindHiddenImplicits: Mode = newMode(24, "FindHiddenImplicits")
 
-  /** Are we in a quote in a pattern? */
-  val QuotedPattern: Mode = newMode(25, "QuotedPattern")
+  /** Are we in a quote the body of quoted expression pattern? */
+  val QuotedExprPattern: Mode = newMode(25, "QuotedExprPattern")
+
+  val QuotedPatternBits: Mode = QuotedExprPattern | QuotedTypePattern
 
   /** Are we typechecking the rhs of an extension method? */
   val InExtensionMethod: Mode = newMode(26, "InExtensionMethod")

compiler/src/dotty/tools/dotc/transform/TreeChecker.scala

@@ -709,7 +709,7 @@ object TreeChecker {
       super.typedQuotePattern(tree, pt)
 
     override def typedSplicePattern(tree: untpd.SplicePattern, pt: Type)(using Context): Tree =
-      assert(ctx.mode.is(Mode.QuotedPattern))
+      assert(ctx.mode.isQuotedPattern)
       def isAppliedIdent(rhs: untpd.Tree): Boolean = rhs match
         case _: Ident => true
         case rhs: GenericApply => isAppliedIdent(rhs.fun)

compiler/src/dotty/tools/dotc/typer/QuotesAndSplices.scala

@@ -78,7 +78,7 @@ trait QuotesAndSplices {
   def typedSplice(tree: untpd.Splice, pt: Type)(using Context): Tree = {
     record("typedSplice")
     checkSpliceOutsideQuote(tree)
-    assert(!ctx.mode.is(Mode.QuotedPattern))
+    assert(!ctx.mode.isQuotedPattern)
     tree.expr match {
       case untpd.Quote(innerExpr, Nil) if innerExpr.isTerm =>
         report.warning("Canceled quote directly inside a splice. ${ '{ XYZ } } is equivalent to XYZ.", tree.srcPos)
@@ -110,8 +110,6 @@ trait QuotesAndSplices {
   def typedSplicePattern(tree: untpd.SplicePattern, pt: Type)(using Context): Tree = {
     record("typedSplicePattern")
     if isFullyDefined(pt, ForceDegree.flipBottom) then
-      def patternOuterContext(ctx: Context): Context =
-        if (ctx.mode.is(Mode.QuotedPattern)) patternOuterContext(ctx.outer) else ctx
       val typedArgs = withMode(Mode.InQuotePatternHoasArgs) {
         tree.args.map {
           case arg: untpd.Ident =>
@@ -125,8 +123,7 @@ trait QuotesAndSplices {
         report.error("References to `var`s cannot be used in higher-order pattern", arg.srcPos)
       val argTypes = typedArgs.map(_.tpe.widenTermRefExpr)
       val patType = if tree.args.isEmpty then pt else defn.FunctionOf(argTypes, pt)
-      val pat = typedPattern(tree.body, defn.QuotedExprClass.typeRef.appliedTo(patType))(
-        using spliceContext.retractMode(Mode.QuotedPattern).addMode(Mode.Pattern).withOwner(patternOuterContext(ctx).owner))
+      val pat = typedPattern(tree.body, defn.QuotedExprClass.typeRef.appliedTo(patType))(using quotePatternSpliceContext)
       val baseType = pat.tpe.baseType(defn.QuotedExprClass)
       val argType = if baseType.exists then baseType.argTypesHi.head else defn.NothingType
       untpd.cpy.SplicePattern(tree)(pat, typedArgs).withType(pt)
@@ -145,7 +142,7 @@ trait QuotesAndSplices {
    *  The prototype must be fully defined to be able to infer the type of `R`.
    */
   def typedAppliedSplice(tree: untpd.Apply, pt: Type)(using Context): Tree = {
-    assert(ctx.mode.is(Mode.QuotedPattern))
+    assert(ctx.mode.isQuotedPattern)
     val untpd.Apply(splice: untpd.SplicePattern, args) = tree: @unchecked
     def isInBraces: Boolean = splice.span.end != splice.body.span.end
     if isInBraces then // ${x}(...) match an application
@@ -166,26 +163,29 @@ trait QuotesAndSplices {
     val typeSymInfo = pt match
       case pt: TypeBounds => pt
       case _ => TypeBounds.empty
+
+    def warnOnInferredBounds(typeSym: Symbol) =
+      if !(typeSymInfo =:= TypeBounds.empty) && !(typeSym.info <:< typeSymInfo) then
+        val (openQuote, closeQuote) = if ctx.mode.is(Mode.QuotedExprPattern) then ("'{", "}") else ("'[", "]")
+        report.warning(em"Ignored bound$typeSymInfo\n\nConsider defining bounds explicitly:\n  $openQuote $typeSym${typeSym.info & typeSymInfo}; ... $closeQuote", tree.srcPos)
+
     getQuotedPatternTypeVariable(tree.name.asTypeName) match
       case Some(typeSym) =>
         checkExperimentalFeature(
           "support for multiple references to the same type (without backticks) in quoted type patterns (SIP-53)",
           tree.srcPos,
           "\n\nSIP-53: https://docs.scala-lang.org/sips/quote-pattern-type-variable-syntax.html")
-        if !(typeSymInfo =:= TypeBounds.empty) && !(typeSym.info <:< typeSymInfo) then
-          report.warning(em"Ignored bound$typeSymInfo\n\nConsider defining bounds explicitly `'{ $typeSym${typeSym.info & typeSymInfo}; ... }`", tree.srcPos)
+        warnOnInferredBounds(typeSym)
         ref(typeSym)
       case None =>
-        def spliceOwner(ctx: Context): Symbol =
-          if (ctx.mode.is(Mode.QuotedPattern)) spliceOwner(ctx.outer) else ctx.owner
+        val spliceContext = quotePatternSpliceContext
         val name = tree.name.toTypeName
         val nameOfSyntheticGiven = PatMatGivenVarName.fresh(tree.name.toTermName)
         val expr = untpd.cpy.Ident(tree)(nameOfSyntheticGiven)
-        val typeSym = newSymbol(spliceOwner(ctx), name, EmptyFlags, typeSymInfo, NoSymbol, tree.span)
+        val typeSym = newSymbol(spliceContext.owner, name, EmptyFlags, typeSymInfo, NoSymbol, tree.span)
         typeSym.addAnnotation(Annotation(New(ref(defn.QuotedRuntimePatterns_patternTypeAnnot.typeRef)).withSpan(tree.span)))
         addQuotedPatternTypeVariable(typeSym)
-        val pat = typedPattern(expr, defn.QuotedTypeClass.typeRef.appliedTo(typeSym.typeRef))(
-            using spliceContext.retractMode(Mode.QuotedPattern).withOwner(spliceOwner(ctx)))
+        val pat = typedPattern(expr, defn.QuotedTypeClass.typeRef.appliedTo(typeSym.typeRef))(using spliceContext)
         pat.select(tpnme.Underlying)
 
   private def checkSpliceOutsideQuote(tree: untpd.Tree)(using Context): Unit =
@@ -454,7 +454,7 @@ trait QuotesAndSplices {
         "\n\nSIP-53: https://docs.scala-lang.org/sips/quote-pattern-type-variable-syntax.html")
 
     val (typeTypeVariables, patternCtx) =
-      val quoteCtx = quotePatternContext()
+      val quoteCtx = quotePatternContext(quoted.isType)
       if untpdTypeVariables.isEmpty then (Nil, quoteCtx)
       else typedBlockStats(untpdTypeVariables)(using quoteCtx)
 
@@ -543,13 +543,26 @@ object QuotesAndSplices {
   def getQuotedPatternTypeVariable(name: TypeName)(using Context): Option[Symbol] =
     ctx.property(TypeVariableKey).get.get(name)
 
-    /** Get the symbol for the quoted pattern type variable if it exists */
+  /** Get the symbol for the quoted pattern type variable if it exists */
   def addQuotedPatternTypeVariable(sym: Symbol)(using Context): Unit =
     ctx.property(TypeVariableKey).get.update(sym.name.asTypeName, sym)
 
-  /** Context used to type the contents of a quoted */
-  def quotePatternContext()(using Context): Context =
+  /** Context used to type the contents of a quote pattern */
+  def quotePatternContext(isTypePattern: Boolean)(using Context): Context =
     quoteContext.fresh.setNewScope
-      .addMode(Mode.QuotedPattern).retractMode(Mode.Pattern)
+      .addMode(if isTypePattern then Mode.QuotedTypePattern else Mode.QuotedExprPattern)
+      .retractMode(Mode.Pattern) // TODO do we need Mode.QuotedPattern?
       .setProperty(TypeVariableKey, collection.mutable.Map.empty)
+
+  /** Context used to type the contents of a quote pattern splice */
+  def quotePatternSpliceContext(using Context): Context =
+    spliceContext
+      .retractMode(Mode.QuotedPatternBits)
+      .addMode(Mode.Pattern)
+      .withOwner(quotePatternOwner(ctx))
+
+  /** First outer context owner that is outside of a quoted pattern context. */
+  private def quotePatternOwner(ctx: Context): Symbol =
+    if ctx.mode.isQuotedPattern then quotePatternOwner(ctx.outer) else ctx.owner
+
 }

compiler/src/dotty/tools/dotc/typer/ReTyper.scala

@@ -121,7 +121,9 @@ class ReTyper(nestingLevel: Int = 0) extends Typer(nestingLevel) with ReChecking
   override def typedQuotePattern(tree: untpd.QuotePattern, pt: Type)(using Context): Tree =
     assertTyped(tree)
     val bindings1 = tree.bindings.map(typed(_))
-    val bodyCtx = quoteContext.retractMode(Mode.Pattern).addMode(Mode.QuotedPattern)
+    val bodyCtx = quoteContext
+      .retractMode(Mode.Pattern)
+      .addMode(if tree.body.isType then Mode.QuotedTypePattern else Mode.QuotedExprPattern)
     val body1 = typed(tree.body, promote(tree).bodyType)(using bodyCtx)
     val quotes1 = typed(tree.quotes, defn.QuotesClass.typeRef)
     untpd.cpy.QuotePattern(tree)(bindings1, body1, quotes1).withType(tree.typeOpt)
@@ -132,7 +134,7 @@ class ReTyper(nestingLevel: Int = 0) extends Typer(nestingLevel) with ReChecking
     val patternTpe =
       if args1.isEmpty then tree.typeOpt
       else defn.FunctionType(args1.size).appliedTo(args1.map(_.tpe) :+ tree.typeOpt)
-    val bodyCtx = spliceContext.addMode(Mode.Pattern).retractMode(Mode.QuotedPattern)
+    val bodyCtx = spliceContext.addMode(Mode.Pattern).retractMode(Mode.QuotedPatternBits)
     val body1 = typed(tree.body, defn.QuotedExprClass.typeRef.appliedTo(patternTpe))(using bodyCtx)
     val args = tree.args.mapconserve(typedExpr(_))
     untpd.cpy.SplicePattern(tree)(body1, args1).withType(tree.typeOpt)

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -560,7 +560,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
         return tree.withType(defn.AnyType)
       if untpd.isVarPattern(tree) && name.isTermName then
         return typed(desugar.patternVar(tree), pt)
-    else if ctx.mode.is(Mode.QuotedPattern) then
+    else if ctx.mode.isQuotedPattern then
       if untpd.isVarPattern(tree) && name.isTypeName then
         return typedQuotedTypeVar(tree, pt)
     end if
@@ -966,7 +966,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
         // so the expected type is the union `Seq[T] | Array[_ <: T]`.
         val ptArg =
           // FIXME(#8680): Quoted patterns do not support Array repeated arguments
-          if ctx.mode.is(Mode.QuotedPattern) then
+          if ctx.mode.isQuotedPattern then
             pt.translateFromRepeated(toArray = false, translateWildcard = true)
           else
             pt.translateFromRepeated(toArray = false, translateWildcard = true)
@@ -2221,7 +2221,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
           val (desugaredArg, argPt) =
             if ctx.mode.is(Mode.Pattern) then
               (if (untpd.isVarPattern(arg)) desugar.patternVar(arg) else arg, tparamBounds)
-            else if ctx.mode.is(Mode.QuotedPattern) then
+            else if ctx.mode.isQuotedPattern then
               (arg, tparamBounds)
             else
               (arg, WildcardType)
@@ -4268,7 +4268,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
               tree.tpe.EtaExpand(tp.typeParamSymbols)
           tree.withType(tp1)
         }
-      if (ctx.mode.is(Mode.Pattern) || ctx.mode.is(Mode.QuotedPattern) || tree1.tpe <:< pt) tree1
+      if (ctx.mode.is(Mode.Pattern) || ctx.mode.isQuotedPattern || tree1.tpe <:< pt) tree1
       else err.typeMismatch(tree1, pt)
     }
 

tests/neg-macros/quote-type-variable-no-inference-2.check

@@ -0,0 +1,13 @@
+-- Warning: tests/neg-macros/quote-type-variable-no-inference-2.scala:5:22 ---------------------------------------------
+5 |    case '{ $_ : F[t, t]; () } => // warn // error
+  |                      ^
+  |                      Ignored bound <: Double
+  |
+  |                      Consider defining bounds explicitly:
+  |                        '{ type t <: Int & Double; ... }
+-- [E057] Type Mismatch Error: tests/neg-macros/quote-type-variable-no-inference-2.scala:5:12 --------------------------
+5 |    case '{ $_ : F[t, t]; () } => // warn // error
+  |            ^
+  |            Type argument t does not conform to upper bound Double in inferred type F[t, t]
+  |
+  | longer explanation available when compiling with `-explain`

tests/neg-macros/quote-type-variable-no-inference-2.scala

@@ -0,0 +1,8 @@
+import scala.quoted.*
+
+def test2(x: Expr[Any])(using Quotes) =
+  x match
+    case '{ $_ : F[t, t]; () } => // warn // error
+    case '{ type u <: Int & Double; $_ : F[u, u] } =>
+
+type F[X <: Int, Y <: Double]

tests/neg-macros/quote-type-variable-no-inference-3.check

@@ -0,0 +1,20 @@
+-- Warning: tests/neg-macros/quote-type-variable-no-inference-3.scala:5:22 ---------------------------------------------
+5 |    case '{ $_ : F[t, t]; () } => // warn // error
+  |                      ^
+  |                      Ignored bound <: Comparable[U]
+  |
+  |                      Consider defining bounds explicitly:
+  |                        '{ type t <: Comparable[U]; ... }
+-- Warning: tests/neg-macros/quote-type-variable-no-inference-3.scala:6:49 ---------------------------------------------
+6 |    case '{ type u <: Comparable[`u`]; $_ : F[u, u] } =>
+  |                                                 ^
+  |                                                 Ignored bound <: Comparable[Any]
+  |
+  |                                                 Consider defining bounds explicitly:
+  |                                                   '{ type u <: Comparable[u] & Comparable[Any]; ... }
+-- [E057] Type Mismatch Error: tests/neg-macros/quote-type-variable-no-inference-3.scala:5:12 --------------------------
+5 |    case '{ $_ : F[t, t]; () } => // warn // error
+  |            ^
+  |            Type argument t does not conform to upper bound Comparable[t] in inferred type F[t, t]
+  |
+  | longer explanation available when compiling with `-explain`

tests/neg-macros/quote-type-variable-no-inference-3.scala

@@ -0,0 +1,8 @@
+import scala.quoted.*
+
+def test2(x: Expr[Any])(using Quotes) =
+  x match
+    case '{ $_ : F[t, t]; () } => // warn // error
+    case '{ type u <: Comparable[`u`]; $_ : F[u, u] } =>
+
+type F[T, U <: Comparable[U]]

tests/neg-macros/quote-type-variable-no-inference.check

@@ -3,7 +3,8 @@
   |                 ^
   |                 Ignored bound <: Double
   |
-  |                 Consider defining bounds explicitly `'{ type t <: Int & Double; ... }`
+  |                 Consider defining bounds explicitly:
+  |                   '[ type t <: Int & Double; ... ]
 -- [E057] Type Mismatch Error: tests/neg-macros/quote-type-variable-no-inference.scala:5:9 -----------------------------
 5 |    case '[ F[t, t] ] => // warn // error // error
   |         ^