Merge pull request #8986 from dotty-staging/disallow-quoted-paterns-that-are-not-supported

Disallow quoted patterns that are not supported

Author: nicolasstucki

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

@@ -240,8 +240,15 @@ trait QuotesAndSplices {
             TypeTree(tree.tpe.dealias).withSpan(tree.span)
           else
             tree
-        case tdef: TypeDef if tdef.symbol.hasAnnotation(defn.InternalQuoted_patternTypeAnnot) =>
-          transformTypeBindingTypeDef(tdef, typePatBuf)
+        case tdef: TypeDef  =>
+          if tdef.symbol.hasAnnotation(defn.InternalQuoted_patternTypeAnnot) then
+            transformTypeBindingTypeDef(tdef, typePatBuf)
+          else if tdef.symbol.isClass then
+            val kind = if tdef.symbol.is(Module) then "objects" else "classes"
+            ctx.error("Implementation restriction: cannot match " + kind, tree.sourcePos)
+            EmptyTree
+          else
+            super.transform(tree)
         case tree @ AppliedTypeTree(tpt, args) =>
             val args1: List[Tree] = args.zipWithConserve(tpt.tpe.typeParams.map(_.paramVarianceSign)) { (arg, v) =>
               arg.tpe match {
@@ -254,6 +261,15 @@ trait QuotesAndSplices {
           if tree.name.isTermName && !tree.nameSpan.isSynthetic && tree.name.startsWith("$") then
             ctx.error("Names cannot start with $ quote pattern ", tree.namePos)
           super.transform(tree)
+        case _: Match =>
+          ctx.error("Implementation restriction: cannot match `match` expressions", tree.sourcePos)
+          EmptyTree
+        case _: Try =>
+          ctx.error("Implementation restriction: cannot match `try` expressions", tree.sourcePos)
+          EmptyTree
+        case _: Return =>
+          ctx.error("Implementation restriction: cannot match `return` statements", tree.sourcePos)
+          EmptyTree
         case _ =>
           super.transform(tree)
       }

tests/neg-macros/quote-pattern-implemnetation-restrictions.scala

@@ -0,0 +1,12 @@
+import scala.quoted._
+
+def f(x: Expr[Any])(using QuoteContext) =
+  x match {
+    case '{ class Foo; () } => // error
+    case '{ object Foo; () } => // error
+    case '{ 1 match { case _ => () } } => // error
+    case '{ try 1 finally () } => // error
+    case '{ try 1 catch { case _ => 4 } } => // error
+    case '{ Nil.map({ case x: Int => () }) } => // error
+    case '{ def f: Int = return 2 } => // error
+  }

tests/pos/quoted-pattern-type.scala

@@ -42,22 +42,6 @@ object Lib {
         z: Expr[T & Int]
         e
 
-      case e @ '{ ($x: Boolean) match { case _ => $y: Int } } =>
-        e: Expr[T & Int]
-        y: Expr[T & Int]
-        e
-
-      case e @ '{ ($x: Boolean) match { case _ => $y } } =>
-        e: Expr[T]
-        y: Expr[T]
-        e
-
-      case e @ '{ try ($x: Boolean) catch { case _ => $y: Int } } =>
-        e: Expr[T & (Boolean | Int)]
-        x: Expr[T & Boolean]
-        y: Expr[T & Int]
-        e
-
     }
   }
 }