Inhibit typer to insert contextual parameters into HOAS pattern arguments

* This commit introduces a new mode InQuotePatternHoasArgs. We use this mode when typing arguments of HOAS patterns so that typer will not insert contextual parameters.
* This commit also Fix a bug where toExpr does not fully replace symbols.

Author: zeptometer

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

@@ -44,6 +44,14 @@ object Mode {
   /** Are we looking for cyclic references? */
   val CheckCyclic: Mode = newMode(5, "CheckCyclic")
 
+  /** We are in arguments of HOAS pattern in quote pattern matching
+   *  e.g. x, y, z in a quote pattern '{ ... $a(x, y, z) ... }
+   *
+   *  This mode keep typer from inserting contextual parameters to a contextual method without arguments.
+   *  (See tests/run-macros/i17905 for motivating examples)
+   */
+  val InQuotePatternHoasArgs: Mode = newMode(6, "InQuotePatternHoasArgs")
+
   /** We are in a pattern alternative */
   val InPatternAlternative: Mode = newMode(7, "InPatternAlternative")
 

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

@@ -112,12 +112,14 @@ trait QuotesAndSplices {
     if isFullyDefined(pt, ForceDegree.flipBottom) then
       def patternOuterContext(ctx: Context): Context =
         if (ctx.mode.is(Mode.QuotedPattern)) patternOuterContext(ctx.outer) else ctx
-      val typedArgs = tree.args.map {
-        case arg: untpd.Ident =>
-          typedExpr(arg)
-        case arg =>
-          report.error("Open pattern expected an identifier", arg.srcPos)
-          EmptyTree
+      val typedArgs = withMode(Mode.InQuotePatternHoasArgs) {
+        tree.args.map {
+          case arg: untpd.Ident =>
+            typedExpr(arg)
+          case arg =>
+            report.error("Open pattern expected an identifier", arg.srcPos)
+            EmptyTree
+        }
       }
       for arg <- typedArgs if arg.symbol.is(Mutable) do // TODO support these patterns. Possibly using scala.quoted.util.Var
         report.error("References to `var`s cannot be used in higher-order pattern", arg.srcPos)

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

@@ -4106,8 +4106,10 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
       wtp match {
         case wtp: ExprType =>
           readaptSimplified(tree.withType(wtp.resultType))
-        case wtp: MethodType if wtp.isImplicitMethod &&
-          ({ resMatch = constrainResult(tree.symbol, wtp, sharpenedPt); resMatch } || !functionExpected) =>
+        case wtp: MethodType
+          if wtp.isImplicitMethod
+          && ({ resMatch = constrainResult(tree.symbol, wtp, sharpenedPt); resMatch} || !functionExpected)
+          && !ctx.mode.is(Mode.InQuotePatternHoasArgs) =>
           if (resMatch || ctx.mode.is(Mode.ImplicitsEnabled))
             adaptNoArgsImplicitMethod(wtp)
           else

compiler/src/scala/quoted/runtime/impl/QuoteMatcher.scala

@@ -566,7 +566,7 @@ object QuoteMatcher {
                  * f has a method type `(x: Int): Int` and  `f` maps to `g`, `p` should hold
                  * `g.apply(0)` because the type of `g` is `Int => Int` due to eta expansion.
                  */
-                case Apply(fun, args) if env.contains(tree.symbol) => transform(fun).select(nme.apply).appliedToArgs(args)
+                case Apply(fun, args) if env.contains(tree.symbol) => transform(fun).select(nme.apply).appliedToArgs(args.map(transform))
                 case tree: Ident => env.get(tree.symbol).flatMap(argsMap.get).getOrElse(tree)
                 case tree => super.transform(tree)
           }.transform(tree)

tests/run-macros/i17905.check

@@ -0,0 +1,3 @@
+case 1: [matched 1st case] another_given outside
+case 2: [matched 2nd case] given outside
+case 3: [matched 1st case] another_given outside

tests/run-macros/i17905/Macro_1.scala

@@ -0,0 +1,10 @@
+import scala.quoted.*
+
+inline def testCtxParam(inline body: Any) = ${ testCtxParamImpl('body) }
+def testCtxParamImpl(body: Expr[Any])(using Quotes): Expr[String] =
+  body match
+    case '{ given i: String = "given"; def g(using s: String) = "placeholder"; $a(g, i): String } =>
+      '{ $a(((s: String) ?=> s"[matched 1st case] ${s}"), "another_given") }
+    case '{ def g(using s: String) = "placeholder"; $a(g): String } =>
+      '{ $a((s: String) ?=> s"[matched 2nd case] ${s}") }
+    case _ => Expr("not matched")

tests/run-macros/i17905/Test_2.scala

@@ -0,0 +1,6 @@
+@main def Test: Unit =
+  println("case 1: " + testCtxParam { given String = "given"; def f(using t: String) = "placeholder"; f + " outside" })
+  given String = "given"
+  println("case 2: " + testCtxParam { def f(using t: String) = "placeholder"; f + " outside" })
+  /* This is expected to match the first case. The current QuoteMatcher identifies a function with a contextual function. */
+  println("case 3: " + testCtxParam { given i: String = "given"; def a(x: String) = "placeholder"; a(i) + " outside" } )