From c79b8e8f4d2eaf9d2095d82810d1b5b8f6383bbb Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Fri, 3 Nov 2023 14:20:13 +0100
Subject: [PATCH] Future migration warning for alphanumeric infix operator

---
 compiler/src/dotty/tools/dotc/typer/Checking.scala   | 12 ++++++------
 .../test/dotty/tools/dotc/CompilationTests.scala     |  1 +
 tests/neg/rewrite-messages.check                     |  2 +-
 tests/rewrites/alphanumeric-infix-operator.check     |  3 +++
 tests/rewrites/alphanumeric-infix-operator.scala     |  3 +++
 5 files changed, 14 insertions(+), 7 deletions(-)
 create mode 100644 tests/rewrites/alphanumeric-infix-operator.check
 create mode 100644 tests/rewrites/alphanumeric-infix-operator.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Checking.scala b/compiler/src/dotty/tools/dotc/typer/Checking.scala
index 5fd1e165cf20..21bf0bc81cd0 100644
--- a/compiler/src/dotty/tools/dotc/typer/Checking.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Checking.scala
@@ -1081,8 +1081,7 @@ trait Checking {
              !name.isOperatorName &&
              !meth.isDeclaredInfix &&
              !meth.maybeOwner.is(Scala2x) &&
-             !infixOKSinceFollowedBy(tree.right) &&
-             sourceVersion.isAtLeast(future) =>
+             !infixOKSinceFollowedBy(tree.right) =>
             val (kind, alternative) =
               if (ctx.mode.is(Mode.Type))
                 ("type", (n: Name) => s"prefix syntax $n[...]")
@@ -1090,12 +1089,13 @@ trait Checking {
                 ("extractor", (n: Name) => s"prefix syntax $n(...)")
               else
                 ("method", (n: Name) => s"method syntax .$n(...)")
-            def rewriteMsg = Message.rewriteNotice("The latter", options = "-deprecation")
-            report.deprecationWarning(
+            def rewriteMsg = Message.rewriteNotice("The latter", version = `future-migration`)
+            report.errorOrMigrationWarning(
               em"""Alphanumeric $kind $name is not declared ${hlAsKeyword("infix")}; it should not be used as infix operator.
                   |Instead, use ${alternative(name)} or backticked identifier `$name`.$rewriteMsg""",
-              tree.op.srcPos)
-            if (ctx.settings.deprecation.value) {
+              tree.op.srcPos,
+              from = future)
+            if sourceVersion == `future-migration` then {
               patch(Span(tree.op.span.start, tree.op.span.start), "`")
               patch(Span(tree.op.span.end, tree.op.span.end), "`")
             }
diff --git a/compiler/test/dotty/tools/dotc/CompilationTests.scala b/compiler/test/dotty/tools/dotc/CompilationTests.scala
index 0491660219b2..5fd3524e208e 100644
--- a/compiler/test/dotty/tools/dotc/CompilationTests.scala
+++ b/compiler/test/dotty/tools/dotc/CompilationTests.scala
@@ -62,6 +62,7 @@ class CompilationTests {
       compileFile("tests/rewrites/rewrites3x-fatal-warnings.scala", defaultOptions.and("-rewrite", "-source", "future-migration", "-Xfatal-warnings")),
       compileFile("tests/rewrites/with-type-operator.scala", defaultOptions.and("-rewrite", "-source", "future-migration")),
       compileFile("tests/rewrites/private-this.scala", defaultOptions.and("-rewrite", "-source", "future-migration")),
+      compileFile("tests/rewrites/alphanumeric-infix-operator.scala", defaultOptions.and("-rewrite", "-source", "future-migration")),
       compileFile("tests/rewrites/filtering-fors.scala", defaultOptions.and("-rewrite", "-source", "3.2-migration")),
       compileFile("tests/rewrites/refutable-pattern-bindings.scala", defaultOptions.and("-rewrite", "-source", "3.2-migration")),
       compileFile("tests/rewrites/i8982.scala", defaultOptions.and("-indent", "-rewrite")),
diff --git a/tests/neg/rewrite-messages.check b/tests/neg/rewrite-messages.check
index 3ee081edbed2..f368c2dc8997 100644
--- a/tests/neg/rewrite-messages.check
+++ b/tests/neg/rewrite-messages.check
@@ -8,4 +8,4 @@
   |    ^^^
   |    Alphanumeric method foo is not declared infix; it should not be used as infix operator.
   |    Instead, use method syntax .foo(...) or backticked identifier `foo`.
-  |    The latter can be rewritten automatically under -rewrite -deprecation.
+  |    The latter can be rewritten automatically under -rewrite -source future-migration.
diff --git a/tests/rewrites/alphanumeric-infix-operator.check b/tests/rewrites/alphanumeric-infix-operator.check
new file mode 100644
index 000000000000..8ff077e856cf
--- /dev/null
+++ b/tests/rewrites/alphanumeric-infix-operator.check
@@ -0,0 +1,3 @@
+extension (x: Int) def foo(y: Int): Int = x + y
+
+def f: Unit = 2 `foo` 4
diff --git a/tests/rewrites/alphanumeric-infix-operator.scala b/tests/rewrites/alphanumeric-infix-operator.scala
new file mode 100644
index 000000000000..450f44834f05
--- /dev/null
+++ b/tests/rewrites/alphanumeric-infix-operator.scala
@@ -0,0 +1,3 @@
+extension (x: Int) def foo(y: Int): Int = x + y
+
+def f: Unit = 2 foo 4