Force .info before creating new synthetic syms

Closes SI-5545. In the long run this should be generalized, as other
phases might suffer from the same problem. Full explanation here:
https://issues.scala-lang.org/browse/SI-5545

3 files changed, 38 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
index 0851dad0c2..88ad458748 100644
--- a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
+++ b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
@@ -511,7 +511,17 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
        *  was both already used for a map and mucho long.  So "sClass" is the
        *  specialized subclass of "clazz" throughout this file.
        */
-      val sClass = clazz.owner.newClass(specializedName(clazz, env0).toTypeName, clazz.pos, (clazz.flags | SPECIALIZED) & ~CASE)
+      
+      // SI-5545: Eliminate classes with the same name loaded from the bytecode already present - all we need to do is
+      // to force .info on them, as their lazy type will be evaluated and the symbols will be eliminated. Unfortunately
+      // evaluating the info after creating the specialized class will mess the specialized class signature, so we'd
+      // better evaluate it before creating the new class symbol 
+      val clazzName = specializedName(clazz, env0).toTypeName
+      val bytecodeClazz = clazz.owner.info.decl(clazzName)      
+      debuglog("Specializing " + clazz + " found " + bytecodeClazz + " already there")
+      bytecodeClazz.info
+      
+      val sClass = clazz.owner.newClass(clazzName, clazz.pos, (clazz.flags | SPECIALIZED) & ~CASE)
 
       def cloneInSpecializedClass(member: Symbol, flagFn: Long => Long) =
         member.cloneSymbol(sClass, flagFn(member.flags | SPECIALIZED))
diff --git a/test/files/run/t5545.check b/test/files/run/t5545.check
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/test/files/run/t5545.check
diff --git a/test/files/run/t5545.scala b/test/files/run/t5545.scala
new file mode 100644
index 0000000000..7efa6d84f1
--- /dev/null
+++ b/test/files/run/t5545.scala
@@ -0,0 +1,27 @@
+import scala.tools.partest._
+import java.io._
+
+object Test extends DirectTest {
+
+  override def extraSettings: String = "-usejavacp -d " + testOutput.path + " -cp " + testOutput.path
+
+  override def code = """
+    // SI-5545
+    trait F[@specialized(Int) T1, R] {
+      def f(v1: T1): R
+      def g = v1 => f(v1)
+    }
+  """.trim
+
+  override def show(): Unit = {
+    // redirect err to out, for logging
+    val prevErr = System.err
+    System.setErr(System.out)
+    compile()
+    // the bug manifests at the second compilation, when the bytecode is already there
+    compile()
+    System.setErr(prevErr)
+  }
+
+  override def isDebug = false // so we don't get the newSettings warning
+}