From fdfa503347b85869363d29ebe9f9dfad5a5004bc Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Tue, 10 Jun 2025 17:49:06 +0200
Subject: [PATCH] Tweak parameter dependency test when typing applications

Fixes #23299
---
 .../dotty/tools/dotc/typer/Applications.scala | 13 +++++++-----
 .../test/dotc/pos-test-pickling.excludelist   |  1 +
 tests/neg/i16842.check                        | 20 ++++---------------
 tests/neg/i16842.scala                        |  2 +-
 tests/pos/i23266.scala                        | 17 ++++++++++++++++
 5 files changed, 31 insertions(+), 22 deletions(-)
 create mode 100644 tests/pos/i23266.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Applications.scala b/compiler/src/dotty/tools/dotc/typer/Applications.scala
index de31936b6e42..b56bf79167a3 100644
--- a/compiler/src/dotty/tools/dotc/typer/Applications.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Applications.scala
@@ -726,11 +726,14 @@ trait Applications extends Compatibility {
           def addTyped(arg: Arg): List[Type] =
             if !formal.isRepeatedParam then checkNoVarArg(arg)
             addArg(typedArg(arg, formal), formal)
-            if methodType.isParamDependent && typeOfArg(arg).exists then
-              // `typeOfArg(arg)` could be missing because the evaluation of `arg` produced type errors
-              formals1.mapconserve(safeSubstParam(_, methodType.paramRefs(n), typeOfArg(arg)))
-            else
-              formals1
+            if methodType.looksParamDependent
+                  // need to handle also false dependencies since we generate TypeTrees from
+                  // formal parameters in makeVarArg. These are not de-aliased, so they might contain
+                  // stray parameter references. Test case is i23266.scala.
+                && typeOfArg(arg).exists
+                  // `typeOfArg(arg)` could be missing because the evaluation of `arg` produced type errors
+            then formals1.mapconserve(safeSubstParam(_, methodType.paramRefs(n), typeOfArg(arg)))
+            else formals1
 
           def missingArg(n: Int): Unit =
             fail(MissingArgument(methodType.paramNames(n), methString))
diff --git a/compiler/test/dotc/pos-test-pickling.excludelist b/compiler/test/dotc/pos-test-pickling.excludelist
index 28bce963bfd1..1a0be6f66183 100644
--- a/compiler/test/dotc/pos-test-pickling.excludelist
+++ b/compiler/test/dotc/pos-test-pickling.excludelist
@@ -139,6 +139,7 @@ parsercombinators-new-syntax.scala
 hylolib-deferred-given
 hylolib-cb
 hylolib
+i23266.scala
 
 # typecheckErrors method unpickling
 i21415.scala
diff --git a/tests/neg/i16842.check b/tests/neg/i16842.check
index 8cad4bc7656f..936b08f95dbb 100644
--- a/tests/neg/i16842.check
+++ b/tests/neg/i16842.check
@@ -1,16 +1,4 @@
--- [E007] Type Mismatch Error: tests/neg/i16842.scala:24:8 -------------------------------------------------------------
-24 |  Liter(SemanticArray[SemanticInt.type], x) // error // error
-   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |        Found:    Int => SemanticArray[SemanticInt.type]
-   |        Required: SemanticArray[SemanticType]
-   |
-   | longer explanation available when compiling with `-explain`
--- [E007] Type Mismatch Error: tests/neg/i16842.scala:24:41 ------------------------------------------------------------
-24 |  Liter(SemanticArray[SemanticInt.type], x) // error // error
-   |                                         ^
-   |                      Found:    (x : List[Expr2[SemanticInt.type]])
-   |                      Required: ty.T
-   |                      Note that implicit conversions were not tried because the result of an implicit conversion
-   |                      must be more specific than ty.T
-   |
-   | longer explanation available when compiling with `-explain`
+-- Error: tests/neg/i16842.scala:24:7 ----------------------------------------------------------------------------------
+24 |  Liter(SemanticArray[SemanticInt.type], x) // error
+   |       ^
+   |       invalid new prefix (dim: Int): SemanticArray[SemanticInt.type] cannot replace ty.type in type ty.T
diff --git a/tests/neg/i16842.scala b/tests/neg/i16842.scala
index 1e7e5cc14339..e9935b46c01d 100644
--- a/tests/neg/i16842.scala
+++ b/tests/neg/i16842.scala
@@ -21,5 +21,5 @@ def typecheckArrayLiter(
     a: ArrayLiter
 ): Liter[SemanticArray[SemanticType]] = {
   val x: List[Expr2[SemanticInt.type]] = List()
-  Liter(SemanticArray[SemanticInt.type], x) // error // error
+  Liter(SemanticArray[SemanticInt.type], x) // error
 }
diff --git a/tests/pos/i23266.scala b/tests/pos/i23266.scala
new file mode 100644
index 000000000000..bc643ac7215d
--- /dev/null
+++ b/tests/pos/i23266.scala
@@ -0,0 +1,17 @@
+
+def kek(t: Table, ids: t.Id*) = ???
+
+trait Table {
+  type Id = String
+}
+
+object Table1 extends Table {
+  val id: Id = "table1_id"
+}
+
+class Table2() extends Table {
+  val id: Id = "table2_id"
+}
+
+val x = kek(Table1, Table1.id)
+val y = kek(Table2(), Table2().id)
\ No newline at end of file