From 3419c00bc0f398e439665c9a384483ee2b226254 Mon Sep 17 00:00:00 2001
From: Tom Hvitved <hvitved@github.com>
Date: Mon, 17 Nov 2025 12:27:53 +0100
Subject: [PATCH] Rust: Use `ToIndex` instead of `FromIndex` in ranked `forex`
 predicates

`ToIndex` makes more sense, since we start the recursion from `0`.
---
 .../internal/typeinference/FunctionType.qll   | 10 ++++-----
 .../typeinference/internal/TypeInference.qll  | 22 +++++++++----------
 2 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/rust/ql/lib/codeql/rust/internal/typeinference/FunctionType.qll b/rust/ql/lib/codeql/rust/internal/typeinference/FunctionType.qll
index 727c99fa8105..e8b44336e76f 100644
--- a/rust/ql/lib/codeql/rust/internal/typeinference/FunctionType.qll
+++ b/rust/ql/lib/codeql/rust/internal/typeinference/FunctionType.qll
@@ -351,7 +351,7 @@ module ArgsAreInstantiationsOf<ArgsAreInstantiationsOfInputSig Input> {
       |
         rnk = 0
         or
-        argsAreInstantiationsOfFromIndex(call, abs, f, rnk - 1)
+        argsAreInstantiationsOfToIndex(call, abs, f, rnk - 1)
       )
     }
 
@@ -360,15 +360,15 @@ module ArgsAreInstantiationsOf<ArgsAreInstantiationsOfInputSig Input> {
     }
   }
 
-  private module ArgIsInstantiationOfFromIndex =
+  private module ArgIsInstantiationOfToIndex =
     ArgIsInstantiationOf<CallAndPos, ArgIsInstantiationOfInput>;
 
   pragma[nomagic]
-  private predicate argsAreInstantiationsOfFromIndex(
+  private predicate argsAreInstantiationsOfToIndex(
     Input::Call call, ImplOrTraitItemNode i, Function f, int rnk
   ) {
     exists(FunctionPosition pos |
-      ArgIsInstantiationOfFromIndex::argIsInstantiationOf(MkCallAndPos(call, pos), i, _) and
+      ArgIsInstantiationOfToIndex::argIsInstantiationOf(MkCallAndPos(call, pos), i, _) and
       call.hasTargetCand(i, f) and
       toCheckRanked(i, f, pos, rnk)
     )
@@ -381,7 +381,7 @@ module ArgsAreInstantiationsOf<ArgsAreInstantiationsOfInputSig Input> {
   pragma[nomagic]
   predicate argsAreInstantiationsOf(Input::Call call, ImplOrTraitItemNode i, Function f) {
     exists(int rnk |
-      argsAreInstantiationsOfFromIndex(call, i, f, rnk) and
+      argsAreInstantiationsOfToIndex(call, i, f, rnk) and
       rnk = max(int r | toCheckRanked(i, f, _, r))
     )
   }
diff --git a/shared/typeinference/codeql/typeinference/internal/TypeInference.qll b/shared/typeinference/codeql/typeinference/internal/TypeInference.qll
index a827ef3cd792..47b80b9dc189 100644
--- a/shared/typeinference/codeql/typeinference/internal/TypeInference.qll
+++ b/shared/typeinference/codeql/typeinference/internal/TypeInference.qll
@@ -578,7 +578,7 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
       }
 
       pragma[nomagic]
-      private predicate satisfiesConcreteTypesFromIndex(
+      private predicate satisfiesConcreteTypesToIndex(
         App app, TypeAbstraction abs, Constraint constraint, int i
       ) {
         exists(Type t, TypePath path |
@@ -586,13 +586,13 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
           if t = abs.getATypeParameter() then any() else app.getTypeAt(path) = t
         ) and
         // Recurse unless we are at the first path
-        if i = 0 then any() else satisfiesConcreteTypesFromIndex(app, abs, constraint, i - 1)
+        if i = 0 then any() else satisfiesConcreteTypesToIndex(app, abs, constraint, i - 1)
       }
 
       /** Holds if all the concrete types in `constraint` also occur in `app`. */
       pragma[nomagic]
       private predicate satisfiesConcreteTypes(App app, TypeAbstraction abs, Constraint constraint) {
-        satisfiesConcreteTypesFromIndex(app, abs, constraint,
+        satisfiesConcreteTypesToIndex(app, abs, constraint,
           max(int i | exists(getNthPath(constraint, i))))
       }
 
@@ -620,7 +620,7 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
       }
 
       pragma[nomagic]
-      private predicate typeParametersEqualFromIndexBase(
+      private predicate typeParametersEqualToIndexBase(
         App app, TypeAbstraction abs, Constraint constraint, TypeParameter tp, TypePath path
       ) {
         path = getNthTypeParameterPath(constraint, tp, 0) and
@@ -630,15 +630,15 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
       }
 
       pragma[nomagic]
-      private predicate typeParametersEqualFromIndex(
+      private predicate typeParametersEqualToIndex(
         App app, TypeAbstraction abs, Constraint constraint, TypeParameter tp, Type t, int i
       ) {
         exists(TypePath path |
           t = app.getTypeAt(path) and
           if i = 0
-          then typeParametersEqualFromIndexBase(app, abs, constraint, tp, path)
+          then typeParametersEqualToIndexBase(app, abs, constraint, tp, path)
           else (
-            typeParametersEqualFromIndex(app, abs, constraint, tp, t, i - 1) and
+            typeParametersEqualToIndex(app, abs, constraint, tp, t, i - 1) and
             path = getNthTypeParameterPath(constraint, tp, i)
           )
         )
@@ -655,19 +655,19 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
           exists(int n | n = max(int i | exists(getNthTypeParameterPath(constraint, tp, i))) |
             // If the largest index is 0, then there are no equalities to check as
             // the type parameter only occurs once.
-            if n = 0 then any() else typeParametersEqualFromIndex(app, abs, constraint, tp, _, n)
+            if n = 0 then any() else typeParametersEqualToIndex(app, abs, constraint, tp, _, n)
           )
         )
       }
 
-      private predicate typeParametersHaveEqualInstantiationFromIndex(
+      private predicate typeParametersHaveEqualInstantiationToIndex(
         App app, TypeAbstraction abs, Constraint constraint, int i
       ) {
         exists(TypeParameter tp | tp = getNthTypeParameter(abs, i) |
           typeParametersEqual(app, abs, constraint, tp) and
           if i = 0
           then any()
-          else typeParametersHaveEqualInstantiationFromIndex(app, abs, constraint, i - 1)
+          else typeParametersHaveEqualInstantiationToIndex(app, abs, constraint, i - 1)
         )
       }
 
@@ -697,7 +697,7 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
           not exists(getNthTypeParameter(abs, _))
           or
           exists(int n | n = max(int i | exists(getNthTypeParameter(abs, i))) |
-            typeParametersHaveEqualInstantiationFromIndex(app, abs, constraint, n)
+            typeParametersHaveEqualInstantiationToIndex(app, abs, constraint, n)
           )
         )
       }