Avoid stacked thisCall contexts (#20488)

AddImplicitArgs can recursively add several implicit parameter lists. We
need to make sure we don't perform a thisCallContext search in another
thisCall context in this case.

Fixes #20483

The original code would back out further and further in the context
chain for every implicit parameter section on the secondary constructor.
Eventually (in this case after 2 times) bad things happen.

Author: odersky

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

@@ -477,7 +477,7 @@ object Contexts {
 
     /** Is the flexible types option set? */
     def flexibleTypes: Boolean = base.settings.YexplicitNulls.value && !base.settings.YnoFlexibleTypes.value
-    
+
     /** Is the best-effort option set? */
     def isBestEffort: Boolean = base.settings.YbestEffort.value
 

compiler/src/dotty/tools/dotc/typer/Implicits.scala

@@ -1077,7 +1077,7 @@ trait Implicits:
     trace(s"search implicit ${pt.show}, arg = ${argument.show}: ${argument.tpe.show}", implicits, show = true) {
       record("inferImplicit")
       assert(ctx.phase.allowsImplicitSearch,
-        if (argument.isEmpty) i"missing implicit parameter of type $pt after typer at phase ${ctx.phase.phaseName}"
+        if (argument.isEmpty) i"missing implicit parameter of type $pt after typer at phase ${ctx.phase}"
         else i"type error: ${argument.tpe} does not conform to $pt${err.whyNoMatchStr(argument.tpe, pt)}")
 
       val usableForInference = pt.exists && !pt.unusableForInference

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -4056,7 +4056,9 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
 
       def dummyArg(tp: Type) = untpd.Ident(nme.???).withTypeUnchecked(tp)
 
-      def addImplicitArgs(using Context) = {
+      val origCtx = ctx
+
+      def addImplicitArgs(using Context) =
         def hasDefaultParams = methPart(tree).symbol.hasDefaultParams
         def implicitArgs(formals: List[Type], argIndex: Int, pt: Type): List[Tree] = formals match
           case Nil => Nil
@@ -4179,15 +4181,20 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
               case _ => retyped
           else issueErrors(tree, args)
         }
-        else tree match {
-          case tree: Block =>
-            readaptSimplified(tpd.Block(tree.stats, tpd.Apply(tree.expr, args)))
-          case tree: NamedArg =>
-            readaptSimplified(tpd.NamedArg(tree.name, tpd.Apply(tree.arg, args)))
-          case _ =>
-            readaptSimplified(tpd.Apply(tree, args))
-        }
-      }
+        else
+          inContext(origCtx):
+            // Reset context in case it was set to a supercall context before.
+            // otherwise the invariant for taking another this or super call context is not met.
+            // Test case is i20483.scala
+            tree match
+              case tree: Block =>
+                readaptSimplified(tpd.Block(tree.stats, tpd.Apply(tree.expr, args)))
+              case tree: NamedArg =>
+                readaptSimplified(tpd.NamedArg(tree.name, tpd.Apply(tree.arg, args)))
+              case _ =>
+                readaptSimplified(tpd.Apply(tree, args))
+      end addImplicitArgs
+
       pt.revealIgnored match {
         case pt: FunProto if pt.applyKind == ApplyKind.Using =>
           // We can end up here if extension methods are called with explicit given arguments.

tests/pos/i20483.scala

@@ -0,0 +1,13 @@
+
+class Foo
+  (x: Option[String])
+  (using Boolean)
+  (using Int)
+  (using Double):
+
+  def this
+    (x: String)
+    (using Boolean)
+    (using Int)
+    (using Double) =
+    this(Some(x))