From f90da3437580fc17e3798935b620090771ef14f1 Mon Sep 17 00:00:00 2001
From: Szymon Rodziewicz <szymonrodant@gmail.com>
Date: Fri, 10 Mar 2023 17:36:15 +0100
Subject: [PATCH] Check if import contains transparent inline in registerImport

---
 .../tools/dotc/transform/CheckUnused.scala    | 29 +++++++++----------
 .../fatal-warnings/i15503f.scala              |  2 +-
 .../fatal-warnings/i15503g.scala              |  4 +--
 3 files changed, 17 insertions(+), 18 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala b/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala
index 376804f291b4..941654649507 100644
--- a/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala
+++ b/compiler/src/dotty/tools/dotc/transform/CheckUnused.scala
@@ -10,7 +10,7 @@ import dotty.tools.dotc.core.Decorators.{em, i}
 import dotty.tools.dotc.core.Flags.*
 import dotty.tools.dotc.core.Phases.Phase
 import dotty.tools.dotc.core.StdNames
-import dotty.tools.dotc.{ast, report}
+import dotty.tools.dotc.report
 import dotty.tools.dotc.reporting.Message
 import dotty.tools.dotc.typer.ImportInfo
 import dotty.tools.dotc.util.{Property, SrcPos}
@@ -365,7 +365,7 @@ object CheckUnused:
 
     /** Register an import */
     def registerImport(imp: tpd.Import)(using Context): Unit =
-      if !tpd.languageImport(imp.expr).nonEmpty && !imp.isGeneratedByEnum then
+      if !tpd.languageImport(imp.expr).nonEmpty && !imp.isGeneratedByEnum && !isTransparentAndInline(imp) then
         impInScope.top += imp
         unusedImport ++= imp.selectors.filter { s =>
           !shouldSelectorBeReported(imp, s) && !isImportExclusion(s)
@@ -431,19 +431,6 @@ object CheckUnused:
           exists
       }
 
-      // not report unused transparent inline imports
-      for {
-        imp <- imports
-        sel <- imp.selectors
-      } {
-        if unusedImport.contains(sel) then
-          val tpd.Import(qual, _) = imp
-          val importedMembers = qual.tpe.member(sel.name).alternatives.map(_.symbol)
-          val isTransparentAndInline = importedMembers.exists(s => s.is(Transparent) && s.is(Inline))
-          if isTransparentAndInline then
-            unusedImport -= sel
-      }
-
       // if there's an outer scope
       if usedInScope.nonEmpty then
         // we keep the symbols not referencing an import in this scope
@@ -518,6 +505,18 @@ object CheckUnused:
     end getUnused
     //============================ HELPERS ====================================
 
+
+    /**
+     * Checks if import selects a def that is transparent and inline
+     */
+    private def isTransparentAndInline(imp: tpd.Import)(using Context): Boolean =
+      (for {
+        sel <- imp.selectors
+      } yield {
+        val qual = imp.expr
+        val importedMembers = qual.tpe.member(sel.name).alternatives.map(_.symbol)
+        importedMembers.exists(s => s.is(Transparent) && s.is(Inline))
+      }).exists(identity)
     /**
      * Heuristic to detect synthetic suffixes in names of symbols
      */
diff --git a/tests/neg-custom-args/fatal-warnings/i15503f.scala b/tests/neg-custom-args/fatal-warnings/i15503f.scala
index db695da3490b..d36cd01be74e 100644
--- a/tests/neg-custom-args/fatal-warnings/i15503f.scala
+++ b/tests/neg-custom-args/fatal-warnings/i15503f.scala
@@ -5,7 +5,7 @@ val default_int = 1
 
 def f1(a: Int) = a // OK
 def f2(a: Int) = 1 // OK
-def f3(a: Int)(using Int) = a // error
+def f3(a: Int)(using Int) = a // OK
 def f4(a: Int)(using Int) = default_int // error
 def f6(a: Int)(using Int) = summon[Int] // OK
 def f7(a: Int)(using Int) = summon[Int] + a // OK
diff --git a/tests/neg-custom-args/fatal-warnings/i15503g.scala b/tests/neg-custom-args/fatal-warnings/i15503g.scala
index d4daea944184..80317f69e794 100644
--- a/tests/neg-custom-args/fatal-warnings/i15503g.scala
+++ b/tests/neg-custom-args/fatal-warnings/i15503g.scala
@@ -5,8 +5,8 @@ val default_int = 1
 
 def f1(a: Int) = a // OK
 def f2(a: Int) = default_int // error
-def f3(a: Int)(using Int) = a // error
-def f4(a: Int)(using Int) = default_int // error // error
+def f3(a: Int)(using Int) = a // OK
+def f4(a: Int)(using Int) = default_int // OK
 def f6(a: Int)(using Int) = summon[Int] // error
 def f7(a: Int)(using Int) = summon[Int] + a // OK