Support use-site meta-annotations

Co-Authored-By: Guillaume Martres <[email protected]>

Author: dwijnand

compiler/src/dotty/tools/dotc/core/Annotations.scala

@@ -87,6 +87,19 @@ object Annotations {
     def sameAnnotation(that: Annotation)(using Context): Boolean =
       symbol == that.symbol && tree.sameTree(that.tree)
 
+    def hasOneOfMetaAnnotation(metaSyms: Symbol*)(using Context): Boolean =
+      def recTp(tp: Type): Boolean = tp.dealiasKeepAnnots match
+        case AnnotatedType(parent, metaAnnot) => metaSyms.exists(metaAnnot.matches) || recTp(parent)
+        case _ => false
+      def rec(tree: Tree): Boolean = methPart(tree) match
+        case New(tpt) => rec(tpt)
+        case Select(qual, _) => rec(qual)
+        case Annotated(arg, metaAnnot) => metaSyms.exists(metaAnnot.tpe.classSymbol.derivesFrom) || rec(arg)
+        case t @ Ident(_) => recTp(t.tpe)
+        case Typed(expr, _) => rec(expr)
+        case _ => false
+      metaSyms.exists(symbol.hasAnnotation) || rec(tree)
+
     /** Operations for hash-consing, can be overridden */
     def hash: Int = System.identityHashCode(this)
     def eql(that: Annotation) = this eq that

compiler/src/dotty/tools/dotc/transform/PostTyper.scala

@@ -1,4 +1,5 @@
-package dotty.tools.dotc
+package dotty.tools
+package dotc
 package transform
 
 import dotty.tools.dotc.ast.{Trees, tpd, untpd, desugar}
@@ -186,12 +187,8 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
     private def removeUnwantedAnnotations(sym: Symbol, metaAnnotSym: Symbol,
         metaAnnotSymBackup: Symbol, keepIfNoRelevantAnnot: Boolean)(using Context): Unit =
       def shouldKeep(annot: Annotation): Boolean =
-        val annotSym = annot.symbol
-        annotSym.hasAnnotation(metaAnnotSym)
-          || annotSym.hasAnnotation(metaAnnotSymBackup)
-          || (keepIfNoRelevantAnnot && {
-            !annotSym.annotations.exists(metaAnnot => defn.FieldAccessorMetaAnnots.contains(metaAnnot.symbol))
-          })
+        annot.hasOneOfMetaAnnotation(metaAnnotSym, metaAnnotSymBackup)
+        || keepIfNoRelevantAnnot && !annot.hasOneOfMetaAnnotation(defn.FieldAccessorMetaAnnots.toList*)
       if sym.annotations.nonEmpty then
         sym.filterAnnotations(shouldKeep(_))
 

compiler/src/dotty/tools/dotc/transform/SymUtils.scala

@@ -271,7 +271,7 @@ object SymUtils:
       self.isAllOf(EnumCase, butNot = JavaDefined)
 
     def annotationsCarrying(meta: ClassSymbol)(using Context): List[Annotation] =
-      self.annotations.filter(_.symbol.hasAnnotation(meta))
+      self.annotations.filter(_.hasOneOfMetaAnnotation(meta))
 
     def withAnnotationsCarrying(from: Symbol, meta: ClassSymbol)(using Context): self.type = {
       self.addAnnotations(from.annotationsCarrying(meta))

tests/run/i12492.check

@@ -0,0 +1,9 @@
+inspecting field brandName
+@MyColumnBase(name="BRAND_NAME")
+inspecting field companyName
+@MyColumnBase(name="COMPANY_NAME")
+inspecting method companyName
+inspecting method brandName
+inspecting constructor MyTable
+inspecting param brandName
+inspecting param companyName

tests/run/i12492/MyColumnBase.java

@@ -0,0 +1,7 @@
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+@Retention(RetentionPolicy.RUNTIME)
+public @interface MyColumnBase {
+    String name() default "";
+}

tests/run/i12492/MyTable.scala

@@ -0,0 +1,36 @@
+import scala.annotation.meta.field
+
+type MyColumn = MyColumnBase @field
+
+class MyTable(
+  @(MyColumnBase @field)(name="BRAND_NAME")
+  val brandName: String,
+  @MyColumn(name="COMPANY_NAME")
+  val companyName: String,
+)
+
+object Test:
+  def main(args: Array[String]): Unit =
+    val clasz = classOf[MyTable]
+
+    for (m <- clasz.getDeclaredFields) {
+      m.setAccessible(true)
+      println(s"inspecting field ${m.getName}")
+      for a <- m.getAnnotations() do
+        println(a)
+    }
+
+    for (m <- clasz.getDeclaredMethods) {
+      m.setAccessible(true)
+      println(s"inspecting method ${m.getName}")
+      for a <- m.getAnnotations() do
+        println(a)
+    }
+
+    for c <- clasz.getDeclaredConstructors do
+      c.setAccessible(true)
+      println(s"inspecting constructor ${c.getName}")
+      for p <- c.getParameters do
+        println(s"inspecting param ${p.getName}")
+        for a <- p.getAnnotations do
+          println(s"annotation $a")