From e6f267c026daf855dde179da6b516c1cc18b2d94 Mon Sep 17 00:00:00 2001
From: Liu Fengyun <liu@fengy.me>
Date: Mon, 20 Jan 2020 14:05:22 +0100
Subject: [PATCH] Fix #8042: add forgotten Java constructor type params

For primary constructor, we always add the class parameters
during parsing. For secondary constructors, we add class parameters
during desugaring.
---
 compiler/src/dotty/tools/dotc/ast/Desugar.scala         | 2 +-
 compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala | 7 +++++--
 tests/pos/i8042/Exception.java                          | 6 ++++++
 3 files changed, 12 insertions(+), 3 deletions(-)
 create mode 100644 tests/pos/i8042/Exception.java

diff --git a/compiler/src/dotty/tools/dotc/ast/Desugar.scala b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
index c1e31140f411..4f149cb4e48c 100644
--- a/compiler/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
@@ -473,7 +473,7 @@ object desugar {
           decompose(
             defDef(
               addEvidenceParams(
-                cpy.DefDef(ddef)(tparams = constrTparams),
+                cpy.DefDef(ddef)(tparams = constrTparams ++ ddef.tparams),
                 evidenceParams(constr1).map(toDefParam(_, keepAnnotations = false)))))
         case stat =>
           stat
diff --git a/compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala b/compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala
index 203fa0c91b84..cbff9f44e16b 100644
--- a/compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/JavaParsers.scala
@@ -112,15 +112,18 @@ object JavaParsers {
         case nil => (EmptyTree, nil)
       }
       var (constr1, stats1) = pullOutFirstConstr(stats)
-      if (constr1 == EmptyTree) constr1 = makeConstructor(List(), tparams)
       // A dummy first constructor is needed for Java classes so that the real constructors see the
       // import of the companion object. The constructor has parameter of type Unit so no Java code
       // can call it.
       // This also avoids clashes between the constructor parameter names and member names.
       if (needsDummyConstr) {
+        if (constr1 == EmptyTree) constr1 = makeConstructor(List(), Nil)
         stats1 = constr1 :: stats1
         constr1 = makeConstructor(List(scalaDot(tpnme.Unit)), tparams, Flags.JavaDefined | Flags.PrivateLocal)
       }
+      else if (constr1 == EmptyTree) {
+        constr1 = makeConstructor(List(), tparams)
+      }
       Template(constr1.asInstanceOf[DefDef], parents, Nil, EmptyValDef, stats1)
     }
 
@@ -506,7 +509,7 @@ object JavaParsers {
         optThrows()
         List {
           atSpan(start) {
-            DefDef(nme.CONSTRUCTOR, parentTParams,
+            DefDef(nme.CONSTRUCTOR, tparams,
                 List(vparams), TypeTree(), methodBody()).withMods(mods)
           }
         }
diff --git a/tests/pos/i8042/Exception.java b/tests/pos/i8042/Exception.java
new file mode 100644
index 000000000000..6fa7745346bb
--- /dev/null
+++ b/tests/pos/i8042/Exception.java
@@ -0,0 +1,6 @@
+public class Exception {
+    public <T> Exception(T actual, T matcher) { }
+
+    public <T> Object foo(T actual, T matcher) { return null; }
+
+}