closes #3890: propagate inferred type parameter...

closes #3890: propagate inferred type parameters to info of undetermined
type parameters. review by imaier.

3 files changed, 28 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/ast/Trees.scala b/src/compiler/scala/tools/nsc/ast/Trees.scala
index 70641f9037..755f798666 100644
--- a/src/compiler/scala/tools/nsc/ast/Trees.scala
+++ b/src/compiler/scala/tools/nsc/ast/Trees.scala
@@ -961,6 +961,21 @@ trait Trees extends reflect.generic.Trees { self: SymbolTable =>
 
   lazy val EmptyTreeTypeSubstituter = new TreeTypeSubstituter(List(), List())
 
+  class TreeSymSubstTraverser(val from: List[Symbol], val to: List[Symbol]) extends Traverser {
+    val subst = new SubstSymMap(from, to)
+    override def traverse(tree: Tree) {
+      if (tree.tpe ne null) tree.tpe = subst(tree.tpe)
+      if (tree.isDef) {
+        val sym = tree.symbol
+        val info1 = subst(sym.info)
+        if (info1 ne sym.info) sym.setInfo(info1)
+      }
+      super.traverse(tree)
+    }
+    override def apply[T <: Tree](tree: T): T = super.apply(tree.duplicate)
+    override def toString() = "TreeSymSubstTraverser("+from+","+to+")"
+  }
+
   /** Substitute symbols in 'from' with symbols in 'to'. Returns a new
    *  tree using the new symbols and whose Ident and Select nodes are
    *  name-consistent with the new symbols.
diff --git a/src/compiler/scala/tools/nsc/typechecker/Infer.scala b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
index 2313822663..dc143666a1 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Infer.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
@@ -1164,7 +1164,15 @@ trait Infer {
           val treeSubst = new TreeTypeSubstituter(okparams, okargs)
           treeSubst.traverse(fn)
           treeSubst.traverseTrees(args)
-          leftUndet
+          if(leftUndet nonEmpty) {  // #3890
+            val leftUndet1 = treeSubst.typeSubst mapOver leftUndet
+            if(leftUndet ne leftUndet1) {
+              val symSubst = new TreeSymSubstTraverser(leftUndet, leftUndet1)
+              symSubst.traverse(fn)
+              symSubst.traverseTrees(args)
+            }
+            leftUndet1
+          } else leftUndet
         } catch {
           case ex: NoInstance =>
             errorTree(fn,
diff --git a/test/files/pos/t3890.scala b/test/files/pos/t3890.scala
new file mode 100644
index 0000000000..bfc4754779
--- /dev/null
+++ b/test/files/pos/t3890.scala
@@ -0,0 +1,4 @@
+object Test {
+ def g[S, T <: S](s: S)(t: T): Unit = println("")
+ g("a")("a") // error: inferred type arguments [java.lang.String] do not conform to method g's type parameter bounds [T <: S]
+}
\ No newline at end of file