From 108be2517049ce566f14cdf41924d0206eeddd60 Mon Sep 17 00:00:00 2001
From: Nicolas Stucki <nicolas.stucki@gmail.com>
Date: Mon, 8 Jun 2020 11:43:50 +0200
Subject: [PATCH] Fix #9100: Add error when experimental macros are not enabled

---
 compiler/src/dotty/tools/dotc/config/Feature.scala |  3 +++
 compiler/src/dotty/tools/dotc/typer/Typer.scala    | 10 ++++++++++
 tests/neg/i9100.scala                              |  3 +++
 tests/semanticdb/expect/Classes.expect.scala       |  2 +-
 tests/semanticdb/expect/Classes.scala              |  2 +-
 tests/semanticdb/metac.expect                      |  6 +++++-
 6 files changed, 23 insertions(+), 3 deletions(-)
 create mode 100644 tests/neg/i9100.scala

diff --git a/compiler/src/dotty/tools/dotc/config/Feature.scala b/compiler/src/dotty/tools/dotc/config/Feature.scala
index 933fd0f372c4..25d79bc50f2f 100644
--- a/compiler/src/dotty/tools/dotc/config/Feature.scala
+++ b/compiler/src/dotty/tools/dotc/config/Feature.scala
@@ -60,6 +60,9 @@ object Feature:
   def dependentEnabled(using Context) =
     enabled(nme.dependent, defn.LanguageExperimentalModule.moduleClass)
 
+  def scala2ExperimentalMacroEnabled(using Context) =
+    enabled("macros".toTermName, defn.LanguageExperimentalModule.moduleClass)
+
   def sourceVersionSetting(using Context): SourceVersion =
     SourceVersion.valueOf(ctx.settings.source.value)
 
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index b89d878e03c1..6d7e9aff4c7a 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -3581,6 +3581,16 @@ class Typer extends Namer
       }
     }
     if ctx.phase.isTyper then
+      call match
+        case untpd.Ident(nme.???) => // Instinsic macros ignored
+        case _ =>
+          if !config.Feature.scala2ExperimentalMacroEnabled then
+            ctx.error(
+              """Scala 2 macro definition needs to be enabled
+                |by making the implicit value scala.language.experimental.macros visible.
+                |This can be achieved by adding the import clause 'import scala.language.experimental.macros'
+                |or by setting the compiler option -language:experimental.macros.
+              """.stripMargin, call.sourcePos)
       call match
         case call: untpd.Ident =>
           typedIdent(call, defn.AnyType)
diff --git a/tests/neg/i9100.scala b/tests/neg/i9100.scala
new file mode 100644
index 000000000000..e830ee40b022
--- /dev/null
+++ b/tests/neg/i9100.scala
@@ -0,0 +1,3 @@
+object FooMacros {
+  def foo[T]: String = macro Foo.fooImpl[T] // error: Scala 2 macro definition needs to be enabled
+}
diff --git a/tests/semanticdb/expect/Classes.expect.scala b/tests/semanticdb/expect/Classes.expect.scala
index 70bc27506c5d..7df634e2808a 100644
--- a/tests/semanticdb/expect/Classes.expect.scala
+++ b/tests/semanticdb/expect/Classes.expect.scala
@@ -1,5 +1,5 @@
 package classes
-
+import scala.language/*->scalaShadowing::language.*/.experimental/*->scalaShadowing::language.experimental.*/.macros/*->scalaShadowing::language.experimental.macros.*/
 class C1/*<-classes::C1#*/(val x1/*<-classes::C1#x1.*/: Int/*->scala::Int#*/) extends AnyVal/*->scala::AnyVal#*//*->scala::AnyVal#`<init>`().*/
 
 class C2/*<-classes::C2#*/(val x2/*<-classes::C2#x2.*/: Int/*->scala::Int#*/) extends AnyVal/*->scala::AnyVal#*//*->scala::AnyVal#`<init>`().*/
diff --git a/tests/semanticdb/expect/Classes.scala b/tests/semanticdb/expect/Classes.scala
index 510c853c0fda..ac0266142174 100644
--- a/tests/semanticdb/expect/Classes.scala
+++ b/tests/semanticdb/expect/Classes.scala
@@ -1,5 +1,5 @@
 package classes
-
+import scala.language.experimental.macros
 class C1(val x1: Int) extends AnyVal
 
 class C2(val x2: Int) extends AnyVal
diff --git a/tests/semanticdb/metac.expect b/tests/semanticdb/metac.expect
index 6bf2e8fe4e3f..32ec79eb6fd4 100644
--- a/tests/semanticdb/metac.expect
+++ b/tests/semanticdb/metac.expect
@@ -340,7 +340,7 @@ Uri => Classes.scala
 Text => empty
 Language => Scala
 Symbols => 106 entries
-Occurrences => 126 entries
+Occurrences => 130 entries
 
 Symbols:
 classes/C1# => final class C1
@@ -452,6 +452,10 @@ local3 => val local local
 
 Occurrences:
 [0:8..0:15): classes <- classes/
+[1:7..1:12): scala -> scala/
+[1:13..1:21): language -> scalaShadowing/language.
+[1:22..1:34): experimental -> scalaShadowing/language.experimental.
+[1:35..1:41): macros -> scalaShadowing/language.experimental.macros.
 [2:6..2:8): C1 <- classes/C1#
 [2:8..2:21): <- classes/C1#`<init>`().
 [2:13..2:15): x1 <- classes/C1#x1.