chore: implicit parameters should warn at call site

Author: hamzaremmal

compiler/src/dotty/tools/dotc/config/MigrationVersion.scala

@@ -32,6 +32,7 @@ enum MigrationVersion(val warnFrom: SourceVersion, val errorFrom: SourceVersion)
   case ParameterEnclosedByParenthesis extends MigrationVersion(future, future)
   case XmlLiteral extends MigrationVersion(future, future)
   case GivenSyntax extends MigrationVersion(future, never)
+  case ImplicitParamsWithoutUsing extends MigrationVersion(future, never)
 
   require(warnFrom.ordinal <= errorFrom.ordinal)
 

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

@@ -126,4 +126,16 @@ trait Migrations:
         patch(Span(pt.args.head.span.start), "using ")
   end contextBoundParams
 
+  /** Report implicit parameter lists and rewrite implicit parameter list to contextual params */
+  def implicitParams(tree: Tree, tp: MethodOrPoly, pt: FunProto)(using Context): Unit =
+    val mversion = mv.ImplicitParamsWithoutUsing
+    if tp.companion == ImplicitMethodType && pt.applyKind != ApplyKind.Using && pt.args.nonEmpty then
+      val rewriteMsg = Message.rewriteNotice("This code", mversion.patchFrom)
+      report.errorOrMigrationWarning(
+        em"Implicit parameters should be provided with a `using` clause.$rewriteMsg", 
+        pt.args.head.srcPos, mversion)
+      if mversion.needsPatch then
+        patch(Span(pt.args.head.span.start), "using ")
+  end implicitParams
+
 end Migrations

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

@@ -4159,6 +4159,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
         def methodStr = methPart(tree).symbol.showLocated
         if matchingApply(wtp, pt) then
           migrate(contextBoundParams(tree, wtp, pt))
+          migrate(implicitParams(tree, wtp, pt))
           if needsTupledDual(wtp, pt) then adapt(tree, pt.tupledDual, locked)
           else tree
         else if wtp.isContextualMethod then

compiler/test/dotty/tools/dotc/CompilationTests.scala

@@ -82,6 +82,7 @@ class CompilationTests {
       compileFile("tests/rewrites/infix-named-args.scala", defaultOptions.and("-rewrite", "-source:3.6-migration")),
       compileFile("tests/rewrites/ambigious-named-tuple-assignment.scala", defaultOptions.and("-rewrite", "-source:3.6-migration")),
       compileFile("tests/rewrites/i21382.scala", defaultOptions.and("-indent", "-rewrite")),
+      compileFile("tests/rewrites/i22440.scala", defaultOptions.and("-rewrite"))
     ).checkRewrites()
   }
 

tests/rewrites/i22440.check

@@ -0,0 +1,5 @@
+//> using options -source future-migration
+
+def foo(implicit x: Int) = ()
+val _ = foo(using 1)
+val _ = foo    (using 1)

tests/rewrites/i22440.scala

@@ -0,0 +1,5 @@
+//> using options -source future-migration
+
+def foo(implicit x: Int) = ()
+val _ = foo(1)
+val _ = foo    (1)

tests/warn/i22440.check

@@ -0,0 +1,5 @@
+-- Warning: tests/warn/i22440.scala:4:12 -------------------------------------------------------------------------------
+4 |val _ = foo(1) // warn
+  |            ^
+  |            Implicit parameters should be provided with a `using` clause.
+  |            This code can be rewritten automatically under -rewrite -source future-migration.

tests/warn/i22440.scala

@@ -0,0 +1,4 @@
+//> using options -source future
+
+def foo(implicit x: Int) = x
+val _ = foo(1) // warn