From 2e4a0701d57df0f5af067f04da35a95b6003578a Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Tue, 28 May 2024 20:38:39 +0200
Subject: [PATCH] Avoid stacked thisCall contexts

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 3 times) bad things happen.
---
 .../src/dotty/tools/dotc/core/Contexts.scala  |  2 +-
 .../dotty/tools/dotc/typer/Implicits.scala    |  2 +-
 .../src/dotty/tools/dotc/typer/Typer.scala    | 27 ++++++++++++-------
 tests/pos/i20483.scala                        | 13 +++++++++
 4 files changed, 32 insertions(+), 12 deletions(-)
 create mode 100644 tests/pos/i20483.scala

diff --git a/compiler/src/dotty/tools/dotc/core/Contexts.scala b/compiler/src/dotty/tools/dotc/core/Contexts.scala
index a5b0e2dba254..79a0b279aefe 100644
--- a/compiler/src/dotty/tools/dotc/core/Contexts.scala
+++ b/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
 
diff --git a/compiler/src/dotty/tools/dotc/typer/Implicits.scala b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
index 3fe8d6fae8a3..cd35825dfae7 100644
--- a/compiler/src/dotty/tools/dotc/typer/Implicits.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Implicits.scala
@@ -1067,7 +1067,7 @@ 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
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index e44da20814dd..9ab5a8ac69df 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/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.
diff --git a/tests/pos/i20483.scala b/tests/pos/i20483.scala
new file mode 100644
index 000000000000..a01a77327181
--- /dev/null
+++ b/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))
\ No newline at end of file