Skip contexts for implicit search when resolving imports

Author: odersky

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

@@ -976,10 +976,23 @@ trait Implicits:
       then return NoMatchingImplicitsFailure
 
       val result0 =
-        try ImplicitSearch(pt, argument, span).bestImplicit
+        // If we are searching implicits when resolving an import symbol, start the search
+        // in the first enclosing context that does not have the same scope as the current
+        // context. Without that precaution, an eligible implicit in the current scope
+        // would cause a cyclic reference error (if the import is named) or cause a
+        // spurious import skip (if the import is a wildcard import). See i1282 for a test case.
+        var searchCtx = ctx
+        if ctx.owner.isImport then
+          while
+            searchCtx = searchCtx.outer
+            (searchCtx.scope eq ctx.scope) && (searchCtx.owner eq ctx.owner.owner)
+          do ()
+
+        try ImplicitSearch(pt, argument, span)(using searchCtx).bestImplicit
         catch case ce: CyclicReference =>
           ce.inImplicitSearch = true
           throw ce
+      end result0
 
       val result =
         result0 match {

tests/pos/i10295.scala

@@ -10,9 +10,11 @@ def doSomething(body: M ?=> Unit) = body(using new M{})
 
 def Test1 =
   given M = new M{}
-  import m.*
-  val x: X = X.foo()
-  println(x)
+  locally {
+    import m.*
+    val x: X = X.foo()
+    println(x)
+  }
 
 def Test2 =
 

tests/pos/i12802.scala

@@ -0,0 +1,9 @@
+import scala.quoted._
+
+object Boo:
+  def foo(using Quotes): Unit =
+    import quotes.reflect._
+    given Option[Symbol] = Some[Symbol](???)
+  def bar(using Quotes): Unit =
+    import quotes.reflect.Symbol
+    given Option[Symbol] = Some[Symbol](???)