From b8a042e663352aea3e83c7ccd6c6fa59f4f433be Mon Sep 17 00:00:00 2001
From: Andrey Vokin <andrey.vokin@jetbrains.com>
Date: Mon, 15 Jun 2026 20:07:58 +0200
Subject: [PATCH] PY-89956 resolve local variable via
 PyDefUseUtil.getLatestDefs instead of PyResolveUtil.scopeCrawlUp

  When a name is defined in the reference's own scope, scopeCrawlUp collects all
  same-name definitions just to find the owner and then narrows to the reaching defs
  anyway; for a variable reassigned N times that makes resolving its N references
  O(N^2) and hangs inspection. Go straight to the control-flow reaching defs for the
  plain local case; everything else falls back to the general path unchanged.

GitOrigin-RevId: 3694fdb0afd6077340e1d75eaf39090fe1f848a9
---
 .../codeInsight/dataflow/scope/Scope.java      |  3 +++
 .../dataflow/scope/impl/ScopeImpl.java         |  8 ++++++++
 .../psi/impl/references/PyReferenceImpl.java   | 18 ++++++++++++++++++
 3 files changed, 29 insertions(+)

diff --git a/python/python-psi-impl/src/com/jetbrains/python/codeInsight/dataflow/scope/Scope.java b/python/python-psi-impl/src/com/jetbrains/python/codeInsight/dataflow/scope/Scope.java
index 8265559da00c..4705984b7b18 100644
--- a/python/python-psi-impl/src/com/jetbrains/python/codeInsight/dataflow/scope/Scope.java
+++ b/python/python-psi-impl/src/com/jetbrains/python/codeInsight/dataflow/scope/Scope.java
@@ -52,6 +52,9 @@ public interface Scope {
 
   boolean containsDeclaration(String name);
 
+  /** Cheap O(1) check whether this scope itself declares a (non-import) named element {@code name}. */
+  boolean declaresName(@NotNull String name);
+
   @NotNull
   List<PyImportedNameDefiner> getImportedNameDefiners();
 
diff --git a/python/python-psi-impl/src/com/jetbrains/python/codeInsight/dataflow/scope/impl/ScopeImpl.java b/python/python-psi-impl/src/com/jetbrains/python/codeInsight/dataflow/scope/impl/ScopeImpl.java
index 09faeea488fa..8d4421d15303 100644
--- a/python/python-psi-impl/src/com/jetbrains/python/codeInsight/dataflow/scope/impl/ScopeImpl.java
+++ b/python/python-psi-impl/src/com/jetbrains/python/codeInsight/dataflow/scope/impl/ScopeImpl.java
@@ -169,6 +169,14 @@ public class ScopeImpl implements Scope {
     return false;
   }
 
+  @Override
+  public boolean declaresName(@NotNull String name) {
+    if (myNamedElements == null) {
+      collectDeclarations();
+    }
+    return myNamedElements.containsKey(name);
+  }
+
   @Override
   public @NotNull List<PyImportedNameDefiner> getImportedNameDefiners() {
     if (myImportedNameDefiners == null) {
diff --git a/python/python-psi-impl/src/com/jetbrains/python/psi/impl/references/PyReferenceImpl.java b/python/python-psi-impl/src/com/jetbrains/python/psi/impl/references/PyReferenceImpl.java
index 2c33c7ac5656..22d1ad948549 100644
--- a/python/python-psi-impl/src/com/jetbrains/python/psi/impl/references/PyReferenceImpl.java
+++ b/python/python-psi-impl/src/com/jetbrains/python/psi/impl/references/PyReferenceImpl.java
@@ -274,6 +274,24 @@ public class PyReferenceImpl implements PsiReferenceEx, PsiPolyVariantReference
       return ((PyFile)realContext).multiResolveName(referencedName);
     }
 
+    // PY-89956 fast path: for a plain local variable, resolve straight to its control-flow
+    // reaching definitions instead of first collecting *all* same-name definitions of the scope
+    final TypeEvalContext typeEvalContext = myContext.getTypeEvalContext();
+    final ScopeOwner owner = ScopeUtil.getScopeOwner(realContext);
+    if (typeEvalContext.maySwitchToAST(realContext) && owner != null && !(owner instanceof PyClass)) {
+      final Scope scope = ControlFlowCache.getScope(owner);
+      if (scope.declaresName(referencedName) && !scope.isGlobal(referencedName) && !scope.isNonlocal(referencedName)) {
+        final List<Instruction> defs =
+          PyDefUseUtil.getLatestDefs(owner, referencedName, realContext, false, true, typeEvalContext).defs();
+        if (!defs.isEmpty() && ContainerUtil.and(defs, i -> i.getElement() instanceof PyTargetExpression)) {
+          final ResolveResultList latest = resolveToLatestDefs(defs, realContext, referencedName, typeEvalContext);
+          if (!latest.isEmpty()) {
+            return latest;
+          }
+        }
+      }
+    }
+
     // here we have an unqualified expr. it may be defined:
     // ...in current file
     final PyResolveProcessor processor = new PyResolveProcessor(referencedName);