Fix #9803: Use right context for reporting ambiguous references

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

@@ -188,7 +188,7 @@ class Typer extends Namer
        */
       def recurAndCheckNewOrShadowed(previous: Type, prevPrec: BindingPrec, prevCtx: Context)(using Context): Type =
         val found = findRefRecur(previous, prevPrec, prevCtx)
-        if found eq previous then checkNewOrShadowed(found, prevPrec)
+        if found eq previous then checkNewOrShadowed(found, prevPrec)(using prevCtx)
         else found
 
       def selection(imp: ImportInfo, name: Name, checkBounds: Boolean): Type =

tests/neg/i9803.check

@@ -0,0 +1,8 @@
+-- [E049] Reference Error: tests/neg/i9803.scala:15:10 -----------------------------------------------------------------
+15 |  println(f421()) // error
+   |          ^^^^
+   |          Reference to f421 is ambiguous,
+   |          it is both imported by name by import bugs.shadowing.x.f421
+   |          and imported by name subsequently by import bugs.shadowing.y.f421
+
+longer explanation available when compiling with `-explain`

tests/neg/i9803.scala

@@ -0,0 +1,16 @@
+package bugs.shadowing
+
+object x {
+  def f421() = 1
+}
+
+object y {
+  def f421() = true
+}
+
+import x.f421
+import y.f421
+
+object test {
+  println(f421()) // error
+}