Also handle imports on parameters of lambdas returned from inline defs

Both i19493 and i19436 require mapping the type of
the expr in an `ImportType` which is itself the info of a `TermRef`.
In the first issue, for the substitution of an inline def parameter proxy.
In the second issue, for the parameter of a lambda returned from an inline def.

Both can be handled in `TypeMap` by mapping over references to `ImportType`s.
The second case also requires modifying `TreeTypeMap#mapType` such that
the logic mapping over imports is done within a `TypeMap` doing the symbol substitutions.

Fixes #19436

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

@@ -68,8 +68,13 @@ class TreeTypeMap(
     }
   }
 
-  def mapType(tp: Type): Type =
-    mapOwnerThis(typeMap(tp).substSym(substFrom, substTo))
+  val mapType: Type => Type =
+    val substMap = new TypeMap():
+      def apply(tp: Type): Type = tp match
+        case tp: TermRef if tp.symbol.isImport => mapOver(tp)
+        case tp => tp.substSym(substFrom, substTo)
+    typeMap.andThen(substMap).andThen(mapOwnerThis)
+  end mapType
 
   private def updateDecls(prevStats: List[Tree], newStats: List[Tree]): Unit =
     if (prevStats.isEmpty) assert(newStats.isEmpty)

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

@@ -6280,6 +6280,12 @@ object Types extends TypeUtils {
       val ctx = this.mapCtx // optimization for performance
       given Context = ctx
       tp match {
+        case tp: TermRef if tp.symbol.isImport =>
+          // see tests/pos/i19493.scala for examples requiring mapping over imports
+          val ImportType(e) = tp.info: @unchecked
+          val e1 = singleton(apply(e.tpe))
+          newImportSymbol(tp.symbol.owner, e1).termRef
+
         case tp: NamedType =>
           if stopBecauseStaticOrLocal(tp) then tp
           else

compiler/src/dotty/tools/dotc/inlines/Inliner.scala

@@ -565,10 +565,6 @@ class Inliner(val call: tpd.Tree)(using Context):
           def apply(t: Type) = t match {
             case t: ThisType => thisProxy.getOrElse(t.cls, t)
             case t: TypeRef => paramProxy.getOrElse(t, mapOver(t))
-            case t: TermRef if t.symbol.isImport =>
-              val ImportType(e) = t.widenTermRefExpr: @unchecked
-              val e1 = singleton(apply(e.tpe))
-              newImportSymbol(ctx.owner, e1).termRef
             case t: SingletonType =>
               if t.termSymbol.isAllOf(InlineParam) then apply(t.widenTermRefExpr)
               else paramProxy.getOrElse(t, mapOver(t))

tests/pos-macros/i19436/Macro_1.scala

@@ -0,0 +1,18 @@
+
+import scala.quoted.*
+import scala.compiletime.summonInline
+
+trait SomeImplicits:
+  given int: Int
+
+object Macro:
+
+  transparent inline def testSummon: SomeImplicits => Int = ${ testSummonImpl }
+
+  private def testSummonImpl(using Quotes): Expr[SomeImplicits => Int] =
+    import quotes.reflect.*
+    '{
+      (x: SomeImplicits) =>
+        import x.given
+        summonInline[Int]
+    }

tests/pos-macros/i19436/Test_2.scala

@@ -0,0 +1,2 @@
+
+def fn: Unit = Macro.testSummon

tests/pos/i19493.scala

@@ -1,4 +1,3 @@
-
 import scala.compiletime.{summonAll, summonInline}
 import deriving.Mirror
 
@@ -39,4 +38,12 @@ object Minimization:
   val a: A = ???
   a.bar
 
+
+  inline def baz() = (x: GivesString) =>
+    import x.aString
+    summon[String] // ok
+    summonInline[String] // was error
+
+  baz()
+
 end Minimization