SI-4827 Corrected positions assigned to constructor's default arg

* Default arguments are always retained on the <init> method (i.e.,
  the class' constructor). Therefore, when the <init> parameters are
  created, we need to use `duplicateAndKeepPositions` to make sure that
  if a default argument is present, its opaque position is retained as
  well. This is necessary because when parameter accessors (i.e.,
  `fieldDefs`) are created, all default arguments are discared ( as you
  can see in the code, the right-hand-side of a `field` is always an
  `EmptyTree`) - see changes in TreeGen.scala

* When constructing the `fieldDefs`, it is important to adapt their
  range position to avoid overlappings with the positions of default
  arguments. It is worth noting that updating the field's end position
  to `vd.rhs.pos.start` would be incorrect, because `askTypeAt(pos)`
  could return the incorrect tree when the position is equal to
  `vd.rhs.pos.start` (because two nodes including that point position
  would exist in the tree, and `CompilerControl.locateTree(pos)` would
  return the first tree that includes the passed `pos`). This is why
  `1` is subtracted to `vd.rhs.pos.start`. Alternatively, we could have
  used `vd.tpt.pos.end` with similar results. However the logic would
  have become slightly more complex as we would need to handle the case
  where `vd.tpt` doesn't have a range position (for instance, this can
  happen if `-Yinfer-argument-types` is enabled). Therefore, subtracting
  `1` from `vd.rhs.pos.start` seemed the cleanest solution at the
  moment. - see changes in TreeGen.scala.

* If the synthetic constructor contains trees with an opaque range
  position (see point above), it must have a transparent position.
  This can only happen if the constructor's parameters' positions are
  considered, which is why we are now passing `vparamss1` to
  `wrappingPos` - see changes in TreeGen.scala.

* The derived primary constructor should have a transparent position
  as it may contain trees with an opaque range position. Hence, the
  `primaryCtor` position is considered for computing the position of the
  derived constructor - see change in Typers.scala.

Finally, below follows the printing of the tree for test t4287, which
you should compare with the one attached with the previous commit
message:

```
[[syntax trees at end of typer]] // Foo.scala
[0:63]package [0:0]<empty> {
  [0:37]class Baz extends [9:37][39]scala.AnyRef {
    [10:20]<paramaccessor> private[this] val f: [14]Int = _;
    [14]<stable> <accessor> <paramaccessor> def f: [14]Int = [14][14]Baz.this.f;
    <10:31>def <init>(<10:31>f: [17]<type: [17]scala.Int> = [23:31]B.a): [9]Baz = <10:31>{
      <10:31><10:31><10:31>Baz.super.<init>();
      <10:31>()
    }
  };
  [6]<synthetic> object Baz extends [6][6]AnyRef {
    [6]def <init>(): [9]Baz.type = [6]{
      [6][6][6]Baz.super.<init>();
      [9]()
    };
    [14]<synthetic> def <init>$default$1: [14]Int = [30]B.a
  };
  [39:63]object B extends [48:63][63]scala.AnyRef {
    [63]def <init>(): [48]B.type = [63]{
      [63][63][63]B.super.<init>();
      [48]()
    };
    [52:61]private[this] val a: [56]Int = [60:61]2;
    [56]<stable> <accessor> def a: [56]Int = [56][56]B.this.a
  }
}
```

You should notice that the default arg of `Baz` constructor now has a
range position. And that explains why the associated test now returns
the right tree when asking hyperlinking at the location of the default
argument.

10 files changed, 100 insertions, 13 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 520b55400c..98706d9ea6 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -1918,7 +1918,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
         val primaryCtor1 = primaryCtor match {
           case DefDef(_, _, _, _, _, Block(earlyVals :+ global.pendingSuperCall, unit)) =>
             val argss = superArgs(parents1.head) getOrElse Nil
-            val pos = wrappingPos(parents1.head.pos, argss.flatten)
+            val pos = wrappingPos(parents1.head.pos, primaryCtor :: argss.flatten).makeTransparent
             val superCall = atPos(pos)(PrimarySuperCall(argss))
             deriveDefDef(primaryCtor)(block => Block(earlyVals :+ superCall, unit) setPos pos) setPos pos
           case _ => primaryCtor
diff --git a/src/reflect/scala/reflect/internal/TreeGen.scala b/src/reflect/scala/reflect/internal/TreeGen.scala
index a0bd64f850..4b8f63bf33 100644
--- a/src/reflect/scala/reflect/internal/TreeGen.scala
+++ b/src/reflect/scala/reflect/internal/TreeGen.scala
@@ -341,11 +341,13 @@ abstract class TreeGen extends macros.TreeBuilder {
 
     // create parameters for <init> as synthetic trees.
     var vparamss1 = mmap(vparamss) { vd =>
-      atPos(vd.pos.focus) {
+      val param = atPos(vd.pos.makeTransparent) {
         val mods = Modifiers(vd.mods.flags & (IMPLICIT | DEFAULTPARAM | BYNAMEPARAM) | PARAM | PARAMACCESSOR)
-        ValDef(mods withAnnotations vd.mods.annotations, vd.name, vd.tpt.duplicate, vd.rhs.duplicate)
+        ValDef(mods withAnnotations vd.mods.annotations, vd.name, vd.tpt.duplicate, duplicateAndKeepPositions(vd.rhs))
       }
+      param
     }
+    
     val (edefs, rest) = body span treeInfo.isEarlyDef
     val (evdefs, etdefs) = edefs partition treeInfo.isEarlyValDef
     val gvdefs = evdefs map {
@@ -378,15 +380,21 @@ abstract class TreeGen extends macros.TreeBuilder {
                                          // this means that we don't know what will be the arguments of the super call
                                          // therefore here we emit a dummy which gets populated when the template is named and typechecked
         Some(
-          // TODO: previously this was `wrappingPos(superPos, lvdefs ::: argss.flatten)`
-          // is it going to be a problem that we can no longer include the `argss`?
-          atPos(wrappingPos(superPos, lvdefs)) (
+          atPos(wrappingPos(superPos, lvdefs ::: vparamss1.flatten).makeTransparent) (
             DefDef(constrMods, nme.CONSTRUCTOR, List(), vparamss1, TypeTree(), Block(lvdefs ::: List(superCall), Literal(Constant())))))
       }
     }
     constr foreach (ensureNonOverlapping(_, parents ::: gvdefs, focus = false))
     // Field definitions for the class - remove defaults.
-    val fieldDefs = vparamss.flatten map (vd => copyValDef(vd)(mods = vd.mods &~ DEFAULTPARAM, rhs = EmptyTree))
+    
+    val fieldDefs = vparamss.flatten map (vd => {
+      val field = copyValDef(vd)(mods = vd.mods &~ DEFAULTPARAM, rhs = EmptyTree)
+      // Prevent overlapping of `field` end's position with default argument's start position.
+      // This is needed for `Positions.Locator(pos).traverse` to return the correct tree when 
+      // the `pos` is a point position with all its values equal to `vd.rhs.pos.start`.
+      if(field.pos.isRange && vd.rhs.pos.isRange) field.pos = field.pos.withEnd(vd.rhs.pos.start - 1)
+      field
+    })
 
     global.Template(parents, self, gvdefs ::: fieldDefs ::: constr ++: etdefs ::: rest)
   }
diff --git a/test/files/presentation/t4287.check b/test/files/presentation/t4287.check
index 80c3e2fb23..a922421e18 100644
--- a/test/files/presentation/t4287.check
+++ b/test/files/presentation/t4287.check
@@ -1,11 +1,11 @@
 reload: Foo.scala
 
-askHyperlinkPos for `f ` at (1,24) Foo.scala
+askHyperlinkPos for `B` at (1,24) Foo.scala
 ================================================================================
-[response] found askHyperlinkPos for `f ` at (1,15) Foo.scala
+[response] found askHyperlinkPos for `B` at (3,8) Foo.scala
 ================================================================================
 
-askHyperlinkPos for `f ` at (1,31) Foo.scala
+askHyperlinkPos for `a` at (1,31) Foo.scala
 ================================================================================
-[response] found askHyperlinkPos for `f ` at (1,15) Foo.scala
+[response] found askHyperlinkPos for `a` at (4,7) Foo.scala
 ================================================================================
diff --git a/test/files/presentation/t4287c.check b/test/files/presentation/t4287c.check
new file mode 100644
index 0000000000..42fc30997d
--- /dev/null
+++ b/test/files/presentation/t4287c.check
@@ -0,0 +1,11 @@
+reload: Foo.scala
+
+askHyperlinkPos for `A` at (1,18) Foo.scala
+================================================================================
+[response] found askHyperlinkPos for `A` at (3,8) Foo.scala
+================================================================================
+
+askHyperlinkPos for `a` at (1,25) Foo.scala
+================================================================================
+[response] found askHyperlinkPos for `a` at (4,7) Foo.scala
+================================================================================
diff --git a/test/files/presentation/t4287c.flags b/test/files/presentation/t4287c.flags
new file mode 100644
index 0000000000..d1a8244169
--- /dev/null
+++ b/test/files/presentation/t4287c.flags
@@ -0,0 +1 @@
+-Yinfer-argument-types
\ No newline at end of file
diff --git a/test/files/presentation/t4287c/Test.scala b/test/files/presentation/t4287c/Test.scala
new file mode 100644
index 0000000000..bec1131c4c
--- /dev/null
+++ b/test/files/presentation/t4287c/Test.scala
@@ -0,0 +1,3 @@
+import scala.tools.nsc.interactive.tests.InteractiveTest
+
+object Test extends InteractiveTest
\ No newline at end of file
diff --git a/test/files/presentation/t4287c/src/Foo.scala b/test/files/presentation/t4287c/src/Foo.scala
new file mode 100644
index 0000000000..26870b5021
--- /dev/null
+++ b/test/files/presentation/t4287c/src/Foo.scala
@@ -0,0 +1,9 @@
+class A(a: Int = A/*#*/.a/*#*/)
+
+object A {
+  val a = 2
+}
+
+class B extends A {
+ def this(a) = this()
+}
\ No newline at end of file
diff --git a/test/files/run/t4287inferredMethodTypes.check b/test/files/run/t4287inferredMethodTypes.check
new file mode 100644
index 0000000000..56e9c097cc
--- /dev/null
+++ b/test/files/run/t4287inferredMethodTypes.check
@@ -0,0 +1,30 @@
+[[syntax trees at end of                     typer]] // newSource1.scala
+[0:92]package [0:0]<empty> {
+  [0:21]class A extends [7:21][23]scala.AnyRef {
+    [8:16]<paramaccessor> private[this] val a: [8]Int = _;
+    <8:20>def <init>(<8:20>a: [11]<type: [11]scala.Int> = [17:20]A.a): [7]A = <8:20>{
+      <8:20><8:20><8:20>A.super.<init>();
+      <8:20>()
+    }
+  };
+  [23:47]object A extends [32:47][49]scala.AnyRef {
+    [49]def <init>(): [32]A.type = [49]{
+      [49][49][49]A.super.<init>();
+      [32]()
+    };
+    [36:45]private[this] val a: [40]Int = [44:45]2;
+    [40]<stable> <accessor> def a: [40]Int = [40][40]A.this.a;
+    [8]<synthetic> def <init>$default$1: [8]Int = [19]A.a
+  };
+  [49:92]class B extends [57:92][65:66]A {
+    [65]def <init>(): [57]B = [65]{
+      [65][65][65]B.super.<init>([65]A.<init>$default$1);
+      [57]()
+    };
+    [70:90]def <init>([79:80]a: [79]Int): [74]B = [84:90]{
+      [84:90][84:90][84]B.this.<init>();
+      [84]()
+    }
+  }
+}
+
diff --git a/test/files/run/t4287inferredMethodTypes.scala b/test/files/run/t4287inferredMethodTypes.scala
new file mode 100644
index 0000000000..f14e672da8
--- /dev/null
+++ b/test/files/run/t4287inferredMethodTypes.scala
@@ -0,0 +1,25 @@
+import scala.tools.partest.DirectTest
+
+object Test extends DirectTest {
+
+  override def extraSettings: String =
+    s"-usejavacp -Yinfer-argument-types -Xprint-pos -Xprint:typer -Yrangepos -Ystop-after:typer -d ${testOutput.path}"
+
+  override def code = """
+class A(a: Int = A.a)
+
+object A {
+  val a = 2
+}
+
+class B extends A {
+ def this(a) = this()
+}
+  """.trim
+
+  override def show(): Unit = {
+    Console.withErr(System.out) {
+      compile()
+    }
+  }
+}
\ No newline at end of file
diff --git a/test/files/run/t5603.check b/test/files/run/t5603.check
index 188f39ff82..760a92567c 100644
--- a/test/files/run/t5603.check
+++ b/test/files/run/t5603.check
@@ -10,10 +10,10 @@
   [87:209]class C extends [94:209][151:159]Greeting {
     [119:139]val nameElse = _;
     [95:101]<paramaccessor> private[this] val i: [98:101]Int = _;
-    <119:139>def <init>([95]i: [98]Int) = <119:139>{
+    <95:139>def <init>(<95:101>i: [98]Int) = <95:139>{
       <119:139>val nameElse = <134:139>"Bob";
       [NoPosition][NoPosition][NoPosition]super.<init>();
-      [94]()
+      <95:139>()
     };
     [168:184]val name = [179:184]"avc";
     [191:203][191:198]println([199:202]msg)