From 030b726ccd18343cc17bcafbeaf8c2ef7bf081b1 Mon Sep 17 00:00:00 2001
From: Jan-Pieter van den Heuvel <jan-pieter@piozum.com>
Date: Tue, 24 Jan 2023 18:31:21 +0100
Subject: [PATCH] Extend the PositionMethods with an exists method, since the
 other methods are not safe to call on non-existing Spans.

Fixes #15927
---
 .../src/scala/quoted/runtime/impl/QuotesImpl.scala  |  1 +
 library/src/scala/quoted/Quotes.scala               |  2 ++
 scaladoc-testcases/src/tests/nonScala3Parent.scala  | 13 +++++++++++++
 .../tools/scaladoc/tasty/ClassLikeSupport.scala     |  2 +-
 .../TranslatableSignaturesTestCases.scala           |  2 ++
 5 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 scaladoc-testcases/src/tests/nonScala3Parent.scala

diff --git a/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala b/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala
index dd6471a882bd..7a88575f71db 100644
--- a/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala
+++ b/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala
@@ -2850,6 +2850,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
 
     given PositionMethods: PositionMethods with
       extension (self: Position)
+        def exists: Boolean = self.exists
         def start: Int = self.start
         def end: Int = self.end
         def sourceFile: SourceFile = self.source
diff --git a/library/src/scala/quoted/Quotes.scala b/library/src/scala/quoted/Quotes.scala
index 48a387e64169..a89470a08dfe 100644
--- a/library/src/scala/quoted/Quotes.scala
+++ b/library/src/scala/quoted/Quotes.scala
@@ -4499,6 +4499,8 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
     /** Extension methods of `Position` */
     trait PositionMethods {
       extension (self: Position)
+        /** Whether we have Span information at all */
+        def exists: Boolean
 
         /** The start offset in the source file */
         def start: Int
diff --git a/scaladoc-testcases/src/tests/nonScala3Parent.scala b/scaladoc-testcases/src/tests/nonScala3Parent.scala
new file mode 100644
index 000000000000..c184a24ff950
--- /dev/null
+++ b/scaladoc-testcases/src/tests/nonScala3Parent.scala
@@ -0,0 +1,13 @@
+package tests
+package nonScala3Parent
+
+import javax.swing.JPanel
+import javax.swing.JFrame
+
+// https://github.com/lampepfl/dotty/issues/15927
+
+trait Foo1 extends Numeric[Any]
+trait Foo2 extends JPanel
+trait Foo3 extends JFrame
+trait Foo4 extends Ordering[Any]
+trait Foo5 extends Enumeration
\ No newline at end of file
diff --git a/scaladoc/src/dotty/tools/scaladoc/tasty/ClassLikeSupport.scala b/scaladoc/src/dotty/tools/scaladoc/tasty/ClassLikeSupport.scala
index 920621b8577c..bff629615db2 100644
--- a/scaladoc/src/dotty/tools/scaladoc/tasty/ClassLikeSupport.scala
+++ b/scaladoc/src/dotty/tools/scaladoc/tasty/ClassLikeSupport.scala
@@ -266,7 +266,7 @@ trait ClassLikeSupport:
     def getParentsAsTreeSymbolTuples: List[(Tree, Symbol)] =
       if noPosClassDefs.contains(c.symbol) then Nil
       else for
-        parentTree <- c.parents if parentTree.pos.start != parentTree.pos.end // We assume here that order is correct
+        parentTree <- c.parents if parentTree.pos.exists && parentTree.pos.start != parentTree.pos.end // We assume here that order is correct
         parentSymbol = parentTree match
           case t: TypeTree => t.tpe.typeSymbol
           case tree if tree.symbol.isClassConstructor => tree.symbol.owner
diff --git a/scaladoc/test/dotty/tools/scaladoc/signatures/TranslatableSignaturesTestCases.scala b/scaladoc/test/dotty/tools/scaladoc/signatures/TranslatableSignaturesTestCases.scala
index ab7c2189e5d5..09f0e08cef29 100644
--- a/scaladoc/test/dotty/tools/scaladoc/signatures/TranslatableSignaturesTestCases.scala
+++ b/scaladoc/test/dotty/tools/scaladoc/signatures/TranslatableSignaturesTestCases.scala
@@ -106,3 +106,5 @@ class ImplicitMembers extends SignatureTest(
   Seq("def"),
   filterFunc = _.toString.endsWith("OuterClass$ImplicitMemberTarget.html")
 )
+
+class NonScala3Parent extends SignatureTest("nonScala3Parent", SignatureTest.all)
\ No newline at end of file