From d981e08d744c524d7ffd04bf8114f727cdb9ea6f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miko=C5=82aj=20Fornal?=
 <24961583+Florian3k@users.noreply.github.com>
Date: Tue, 22 Jul 2025 12:55:45 +0200
Subject: [PATCH] Compare span points in pathTo to determine best span (#23581)

Closes #22207
[Cherry-picked 98c594f39d38a859719f09f39124d56dbb1ed755]
---
 .../dotty/tools/dotc/ast/NavigateAST.scala    | 20 ++++++++---
 .../tools/pc/tests/hover/HoverTermSuite.scala | 36 +++++++++++++++++++
 2 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/ast/NavigateAST.scala b/compiler/src/dotty/tools/dotc/ast/NavigateAST.scala
index 90bd9b7923ae..861db55b1903 100644
--- a/compiler/src/dotty/tools/dotc/ast/NavigateAST.scala
+++ b/compiler/src/dotty/tools/dotc/ast/NavigateAST.scala
@@ -94,7 +94,8 @@ object NavigateAST {
       * When choosing better fit we compare spans. If candidate span has starting or ending point inside (exclusive)
       * current best fit it is selected as new best fit. This means that same spans are failing the first predicate.
       *
-      * In case when spans start and end at same offsets we prefer non synthethic one.
+      * In case when spans start and end at same offsets we prefer non synthethic one,
+      * and then one with better point (see isBetterPoint below).
       */
     def isBetterFit(currentBest: List[Positioned], candidate: List[Positioned]): Boolean =
       if currentBest.isEmpty && candidate.nonEmpty then true
@@ -102,9 +103,20 @@ object NavigateAST {
         val bestSpan = currentBest.head.span
         val candidateSpan = candidate.head.span
 
-        bestSpan != candidateSpan &&
-          envelops(bestSpan, candidateSpan) ||
-          bestSpan.contains(candidateSpan) && bestSpan.isSynthetic && !candidateSpan.isSynthetic
+        def isBetterPoint =
+          // Given two spans with same end points,
+          // we compare their points in relation to the point we are looking for (span.point)
+          // The candidate (candidateSpan.point) is better than what we have so far (bestSpan.point), when:
+          // 1) candidate is closer to target from the right
+          span.point <= candidateSpan.point && candidateSpan.point < bestSpan.point
+          // 2) candidate is closer to target from the left
+          || bestSpan.point < candidateSpan.point && candidateSpan.point <= span.point
+          // 3) candidate is to on the left side of target, and best so far is on the right
+          || candidateSpan.point <= span.point && span.point < bestSpan.point
+
+        bestSpan != candidateSpan && envelops(bestSpan, candidateSpan)
+        || bestSpan.contains(candidateSpan) && bestSpan.isSynthetic && !candidateSpan.isSynthetic
+        || candidateSpan.start == bestSpan.start && candidateSpan.end == bestSpan.end && isBetterPoint
       else false
 
     def isRecoveryTree(sel: untpd.Select): Boolean =
diff --git a/presentation-compiler/test/dotty/tools/pc/tests/hover/HoverTermSuite.scala b/presentation-compiler/test/dotty/tools/pc/tests/hover/HoverTermSuite.scala
index e0501d4c9496..3e3019e80ff7 100644
--- a/presentation-compiler/test/dotty/tools/pc/tests/hover/HoverTermSuite.scala
+++ b/presentation-compiler/test/dotty/tools/pc/tests/hover/HoverTermSuite.scala
@@ -747,3 +747,39 @@ class HoverTermSuite extends BaseHoverSuite:
          |""".stripMargin,
          "def substring(x$0: Int, x$1: Int): String".hover
     )
+
+  @Test def `multiple-valdefs-1` =
+    check(
+      """|object O {
+         |  val x@@x, yy, zz = 1
+         |}
+         |""".stripMargin,
+      "val xx: Int".hover
+    )
+
+  @Test def `multiple-valdefs-2` =
+    check(
+      """|object O {
+         |  val xx, y@@y, zz = 1
+         |}
+         |""".stripMargin,
+      "val yy: Int".hover
+    )
+
+  @Test def `multiple-valdefs-3` =
+    check(
+      """|object O {
+         |  val xx, yy, z@@z = 1
+         |}
+         |""".stripMargin,
+      "val zz: Int".hover
+    )
+
+  @Test def `multiple-valdefs-4` =
+    check(
+      """|object O {
+         |  val xx, thisIsAVeryLongNa@@me, zz = 1
+         |}
+         |""".stripMargin,
+      "val thisIsAVeryLongName: Int".hover
+    )