Fix #3559: fix scope for typing this(...) in 2nd constructor

The scope for typing `this(...)` should include both
constructor params and local defs. The latter are
included to provide more friendly error messages
for references to local definitions.

Author: liufengyun

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

@@ -381,6 +381,8 @@ object Contexts {
       superOrThisCallContext(owner, constrCtx.scope)
         .setTyperState(typerState)
         .setGadt(gadt)
+        .fresh
+        .setScope(this.scope)
     }
 
     /** The super- or this-call context with given owner and locals. */

tests/neg/3559.check

@@ -0,0 +1,4 @@
+-- Error: tests/neg/3559.scala:3:9 -------------------------------------------------------------------------------------
+3 |    this(b)           // error: forward reference not allowed from self constructor invocation
+  |         ^
+  |         forward reference not allowed from self constructor invocation

tests/neg/3559.scala

@@ -0,0 +1,6 @@
+class A(a: Any) {
+  def this() = {
+    this(b)           // error: forward reference not allowed from self constructor invocation
+    def b = new {}
+  }
+}