Improve type inference of quote pattern splices

Infer higher bound for type splices. This means that when type information is not given
the pattern should match all term that could fit in this hole.

Author: nicolasstucki

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

@@ -73,7 +73,7 @@ trait QuotesAndSplices {
       case _ =>
     }
     if (ctx.mode.is(Mode.QuotedPattern))
-      if (isFullyDefined(pt, ForceDegree.all)) {
+      if (isFullyDefined(pt, ForceDegree.flipBottom)) {
         def spliceOwner(ctx: Context): Symbol =
           if (ctx.mode.is(Mode.QuotedPattern)) spliceOwner(ctx.outer) else ctx.owner
         val pat = typedPattern(tree.expr, defn.QuotedExprClass.typeRef.appliedTo(pt))(

tests/run-macros/quote-matcher-inference/Macro_1.scala

@@ -0,0 +1,15 @@
+import scala.quoted._
+
+
+object Macros {
+
+  inline def g(inline x: Unit): Unit = ${impl('x)}
+
+  private def impl(x: Expr[Any])(using QuoteContext): Expr[Any] = {
+    x match
+      case '{ println(f($y)) } => y
+  }
+
+}
+
+def f[T](x: T): T = x

tests/run-macros/quote-matcher-inference/Test_2.scala

@@ -0,0 +1,10 @@
+import Macros._
+
+
+object Test {
+
+  def main(args: Array[String]): Unit = {
+    g(println(f((5))))
+  }
+
+}