Find more looping implicits

 1. Also check apply methods of companions of implicit or given classes.
    Specifically apply methods of implicit Conversions.

 2. Look inside Inlined nodes to detect loops.

Fixes #15474
Fixes #10947

Author: odersky

compiler/src/dotty/tools/dotc/transform/CheckLoopingImplicits.scala

@@ -6,7 +6,7 @@ import MegaPhase.MiniPhase
 import Contexts.*, Types.*, Symbols.*, SymDenotations.*, Flags.*
 import ast.*
 import Decorators.*
-
+import StdNames.*
 
 object CheckLoopingImplicits:
   val name: String = "checkLoopingImplicits"
@@ -60,6 +60,9 @@ class CheckLoopingImplicits extends MiniPhase:
       case Block(stats, expr) =>
         stats.foreach(checkNotLooping)
         checkNotLooping(expr)
+      case Inlined(_, bindings, expr) =>
+        bindings.foreach(checkNotLooping)
+        checkNotLooping(expr)
       case Typed(expr, _) =>
         checkNotLooping(expr)
       case Assign(lhs, rhs) =>
@@ -84,7 +87,9 @@ class CheckLoopingImplicits extends MiniPhase:
         checkNotLooping(t.rhs)
       case _ =>
 
-    if sym.isOneOf(GivenOrImplicit | Lazy | ExtensionMethod) then
+    if sym.isOneOf(GivenOrImplicit | Lazy | ExtensionMethod)
+      || sym.name == nme.apply && sym.owner.is(Module) && sym.owner.sourceModule.isOneOf(GivenOrImplicit)
+    then
       checkNotLooping(mdef.rhs)
     mdef
   end transform

tests/neg-custom-args/fatal-warnings/i15474.scala

@@ -0,0 +1,12 @@
+import scala.language.implicitConversions
+
+given Conversion[ String, Int ] with
+  def apply(from: String): Int = from.toInt   // error
+
+object Prices {
+  opaque type Price = BigDecimal
+
+  object Price{
+    given Ordering[Price] = summon[Ordering[BigDecimal]] // error
+  }
+}