Explicitly provide the given QuoteContext of the splice

 * Avoids leaking implementation details of scala.internal.quoted.CompileTime.exprSplice,
   such as exprSplice taking a ?=> function argument
 * Provide meaningful names for QuoteContext synthesized by within `${ ... }`

Author: nicolasstucki

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

@@ -83,7 +83,20 @@ trait QuotesAndSplices {
           else if (!c.outer.owner.is(Package)) markAsMacro(c.outer)
         markAsMacro(ctx)
       }
-      typedApply(untpd.Apply(untpd.ref(defn.InternalQuoted_exprSplice.termRef), tree.expr), pt)(spliceContext).withSpan(tree.span)
+
+      // Explicitly provide the given QuoteContext of the splice.
+      //  * Avoids leaking implementation details of scala.internal.quoted.CompileTime.exprSplice,
+      //    such as exprSplice taking a ?=> function argument
+      //  * Provide meaningful names for QuoteContext synthesized by within `${ ... }`
+      //  * TODO preserve QuoteContext.tasty path dependent type (see comment below and #8045)
+      val qctxParamName = NameKinds.UniqueName.fresh(s"qctx${level - 1}_".toTermName)
+      // TODO: Refine QuoteContext with the tasty context that the quote reacived
+      //       If encoloseing quote recieves `qctx` then this type should be `QuoteContext { val tasty: qxtx.tasty.type }`
+      val qctxParamTpt = untpd.TypedSplice(TypeTree(defn.QuoteContextClass.typeRef))
+      val qctxParam = untpd.makeParameter(qctxParamName, qctxParamTpt, untpd.Modifiers(Given))
+      val expr = untpd.Function(List(qctxParam), tree.expr).withSpan(tree.span)
+
+      typedApply(untpd.Apply(untpd.ref(defn.InternalQuoted_exprSplice.termRef), expr), pt)(spliceContext).withSpan(tree.span)
     }
   }
 

tests/run-staging/quote-nested-2.check

@@ -1,4 +1,4 @@
 ((qctx: scala.quoted.QuoteContext) => {
   val a: scala.quoted.Expr[scala.Int] = scala.internal.quoted.CompileTime.exprQuote[scala.Int](4) given (qctx)
-  ((evidence$2: scala.quoted.QuoteContext) => a) given (qctx)
+  ((qctx1_$1: scala.quoted.QuoteContext) => a) given (qctx)
 })

tests/run-staging/quote-nested-5.check

@@ -1,4 +1,4 @@
 ((qctx: scala.quoted.QuoteContext) => {
   val a: scala.quoted.Expr[scala.Int] = scala.internal.quoted.CompileTime.exprQuote[scala.Int](4) given (qctx)
-  ((qctx2: scala.quoted.QuoteContext) => ((evidence$3: scala.quoted.QuoteContext) => a) given (qctx2)) given (qctx)
+  ((qctx2: scala.quoted.QuoteContext) => ((qctx1_$1: scala.quoted.QuoteContext) => a) given (qctx2)) given (qctx)
 })