diff --git a/rust/ql/lib/codeql/rust/dataflow/internal/Node.qll b/rust/ql/lib/codeql/rust/dataflow/internal/Node.qll
index cc738d1dc86..f2f6fa1b0d8 100644
--- a/rust/ql/lib/codeql/rust/dataflow/internal/Node.qll
+++ b/rust/ql/lib/codeql/rust/dataflow/internal/Node.qll
@@ -230,7 +230,7 @@ final class ExprArgumentNode extends ArgumentNode, ExprNode {
   ExprArgumentNode() {
     isArgumentForCall(n, call_, pos_) and
     not TypeInference::implicitDeref(n) and
-    not TypeInference::implicitBorrow(n)
+    not TypeInference::implicitBorrow(n, _)
   }
 
   override predicate isArgumentOf(DataFlowCall call, RustDataFlow::ArgumentPosition pos) {
@@ -579,7 +579,7 @@ newtype TNode =
     TypeInference::implicitDeref(n) and
     borrow = false
     or
-    TypeInference::implicitBorrow(n) and
+    TypeInference::implicitBorrow(n, _) and
     borrow = true
   } or
   TDerefOutNode(DerefExpr de, Boolean isPost) or
diff --git a/rust/ql/lib/codeql/rust/internal/Type.qll b/rust/ql/lib/codeql/rust/internal/Type.qll
index 83dcfff8c3a..b4907dee172 100644
--- a/rust/ql/lib/codeql/rust/internal/Type.qll
+++ b/rust/ql/lib/codeql/rust/internal/Type.qll
@@ -226,22 +226,12 @@ TypeParamTypeParameter getArrayTypeParameter() {
 
 abstract class RefType extends StructType { }
 
-pragma[nomagic]
-TypeParamTypeParameter getRefTypeParameter() {
-  result = any(RefType t).getPositionalTypeParameter(0)
-}
-
 class RefMutType extends RefType {
   RefMutType() { this.getStruct() instanceof Builtins::RefMutType }
 
   override string toString() { result = "&mut" }
 }
 
-pragma[nomagic]
-TypeParamTypeParameter getRefMutTypeParameter() {
-  result = any(RefMutType t).getPositionalTypeParameter(0)
-}
-
 class RefSharedType extends RefType {
   RefSharedType() { this.getStruct() instanceof Builtins::RefSharedType }
 
@@ -249,8 +239,15 @@ class RefSharedType extends RefType {
 }
 
 pragma[nomagic]
-TypeParamTypeParameter getRefSharedTypeParameter() {
-  result = any(RefSharedType t).getPositionalTypeParameter(0)
+RefType getRefType(boolean isMutable) {
+  isMutable = true and result instanceof RefMutType
+  or
+  isMutable = false and result instanceof RefSharedType
+}
+
+pragma[nomagic]
+TypeParamTypeParameter getRefTypeParameter(boolean isMutable) {
+  result = getRefType(isMutable).getPositionalTypeParameter(0)
 }
 
 /**
diff --git a/rust/ql/lib/codeql/rust/internal/TypeInference.qll b/rust/ql/lib/codeql/rust/internal/TypeInference.qll
index a004b2cbf4f..5b0ed687357 100644
--- a/rust/ql/lib/codeql/rust/internal/TypeInference.qll
+++ b/rust/ql/lib/codeql/rust/internal/TypeInference.qll
@@ -501,9 +501,9 @@ module CertainTypeInference {
         prefix1.isEmpty() and
         if ip.isRef()
         then
-          if ip.isMut()
-          then prefix2 = TypePath::singleton(getRefMutTypeParameter())
-          else prefix2 = TypePath::singleton(getRefSharedTypeParameter())
+          exists(boolean isMutable | if ip.isMut() then isMutable = true else isMutable = false |
+            prefix2 = TypePath::singleton(getRefTypeParameter(isMutable))
+          )
         else prefix2.isEmpty()
       )
   }
@@ -726,9 +726,9 @@ private predicate typeEquality(AstNode n1, TypePath prefix1, AstNode n2, TypePat
     any(RefPat rp |
       n1 = rp.getPat() and
       prefix1.isEmpty() and
-      if rp.isMut()
-      then prefix2 = TypePath::singleton(getRefMutTypeParameter())
-      else prefix2 = TypePath::singleton(getRefSharedTypeParameter())
+      exists(boolean isMutable | if rp.isMut() then isMutable = true else isMutable = false |
+        prefix2 = TypePath::singleton(getRefTypeParameter(isMutable))
+      )
     )
   or
   exists(int i, int arity |
@@ -1272,29 +1272,31 @@ private predicate isComplexRootStripped(TypePath path, Type type) {
 
 private newtype TBorrowKind =
   TNoBorrowKind() or
-  TSharedBorrowKind() or
-  TMutBorrowKind()
+  TSomeBorrowKind(Boolean isMutable)
 
 private class BorrowKind extends TBorrowKind {
   predicate isNoBorrow() { this = TNoBorrowKind() }
 
+  predicate isSharedBorrow() { this = TSomeBorrowKind(false) }
+
+  predicate isMutableBorrow() { this = TSomeBorrowKind(true) }
+
   RefType getRefType() {
-    this = TSharedBorrowKind() and
-    result instanceof RefSharedType
-    or
-    this = TMutBorrowKind() and
-    result instanceof RefMutType
+    exists(boolean isMutable |
+      this = TSomeBorrowKind(isMutable) and
+      result = getRefType(isMutable)
+    )
   }
 
   string toString() {
-    this = TNoBorrowKind() and
+    this.isNoBorrow() and
     result = ""
     or
-    this = TSharedBorrowKind() and
-    result = "&"
-    or
-    this = TMutBorrowKind() and
+    this.isMutableBorrow() and
     result = "&mut"
+    or
+    this.isSharedBorrow() and
+    result = "&"
   }
 }
 
@@ -1559,7 +1561,7 @@ private module MethodResolution {
         this.hasNoCompatibleTargetMutBorrow(derefChain0) and
         t0 = this.getACandidateReceiverTypeAtNoBorrow(derefChain0, path0)
       |
-        path0.isCons(getRefTypeParameter(), path) and
+        path0.isCons(getRefTypeParameter(_), path) and
         result = t0 and
         derefChain = derefChain0 + ".ref"
         or
@@ -1733,13 +1735,14 @@ private module MethodResolution {
       string derefChain, TypePath strippedTypePath, Type strippedType, int n
     ) {
       this.hasNoCompatibleTargetNoBorrow(derefChain) and
-      strippedType = this.getComplexStrippedType(derefChain, TSharedBorrowKind(), strippedTypePath) and
+      strippedType =
+        this.getComplexStrippedType(derefChain, TSomeBorrowKind(false), strippedTypePath) and
       n = -1
       or
       this.hasNoCompatibleTargetSharedBorrowToIndex(derefChain, strippedTypePath, strippedType,
         n - 1) and
       exists(Type t | t = getNthLookupType(strippedType, n) |
-        this.hasNoCompatibleNonBlanketLikeTargetCheck(derefChain, TSharedBorrowKind(),
+        this.hasNoCompatibleNonBlanketLikeTargetCheck(derefChain, TSomeBorrowKind(false),
           strippedTypePath, t)
       )
     }
@@ -1762,12 +1765,13 @@ private module MethodResolution {
       string derefChain, TypePath strippedTypePath, Type strippedType, int n
     ) {
       this.hasNoCompatibleTargetSharedBorrow(derefChain) and
-      strippedType = this.getComplexStrippedType(derefChain, TMutBorrowKind(), strippedTypePath) and
+      strippedType =
+        this.getComplexStrippedType(derefChain, TSomeBorrowKind(true), strippedTypePath) and
       n = -1
       or
       this.hasNoCompatibleTargetMutBorrowToIndex(derefChain, strippedTypePath, strippedType, n - 1) and
       exists(Type t | t = getNthLookupType(strippedType, n) |
-        this.hasNoCompatibleNonBlanketLikeTargetCheck(derefChain, TMutBorrowKind(),
+        this.hasNoCompatibleNonBlanketLikeTargetCheck(derefChain, TSomeBorrowKind(true),
           strippedTypePath, t)
       )
     }
@@ -1790,14 +1794,15 @@ private module MethodResolution {
       string derefChain, TypePath strippedTypePath, Type strippedType, int n
     ) {
       this.hasNoCompatibleTargetNoBorrow(derefChain) and
-      strippedType = this.getComplexStrippedType(derefChain, TSharedBorrowKind(), strippedTypePath) and
+      strippedType =
+        this.getComplexStrippedType(derefChain, TSomeBorrowKind(false), strippedTypePath) and
       n = -1
       or
       this.hasNoCompatibleNonBlanketTargetSharedBorrowToIndex(derefChain, strippedTypePath,
         strippedType, n - 1) and
       exists(Type t | t = getNthLookupType(strippedType, n) |
-        this.hasNoCompatibleNonBlanketTargetCheck(derefChain, TSharedBorrowKind(), strippedTypePath,
-          t)
+        this.hasNoCompatibleNonBlanketTargetCheck(derefChain, TSomeBorrowKind(false),
+          strippedTypePath, t)
       )
     }
 
@@ -1819,13 +1824,15 @@ private module MethodResolution {
       string derefChain, TypePath strippedTypePath, Type strippedType, int n
     ) {
       this.hasNoCompatibleNonBlanketTargetSharedBorrow(derefChain) and
-      strippedType = this.getComplexStrippedType(derefChain, TMutBorrowKind(), strippedTypePath) and
+      strippedType =
+        this.getComplexStrippedType(derefChain, TSomeBorrowKind(true), strippedTypePath) and
       n = -1
       or
       this.hasNoCompatibleNonBlanketTargetMutBorrowToIndex(derefChain, strippedTypePath,
         strippedType, n - 1) and
       exists(Type t | t = getNthLookupType(strippedType, n) |
-        this.hasNoCompatibleNonBlanketTargetCheck(derefChain, TMutBorrowKind(), strippedTypePath, t)
+        this.hasNoCompatibleNonBlanketTargetCheck(derefChain, TSomeBorrowKind(true),
+          strippedTypePath, t)
       )
     }
 
@@ -1856,17 +1863,17 @@ private module MethodResolution {
     pragma[nomagic]
     Type getACandidateReceiverTypeAt(string derefChain, BorrowKind borrow, TypePath path) {
       result = this.getACandidateReceiverTypeAtNoBorrow(derefChain, path) and
-      borrow = TNoBorrowKind()
+      borrow.isNoBorrow()
       or
       exists(RefType rt |
         // first try shared borrow
         this.supportsAutoDerefAndBorrow() and
         this.hasNoCompatibleTargetNoBorrow(derefChain) and
-        borrow = TSharedBorrowKind()
+        borrow.isSharedBorrow()
         or
         // then try mutable borrow
         this.hasNoCompatibleTargetSharedBorrow(derefChain) and
-        borrow = TMutBorrowKind()
+        borrow.isMutableBorrow()
       |
         rt = borrow.getRefType() and
         (
@@ -1899,9 +1906,8 @@ private module MethodResolution {
       receiver = this.getArg(any(ArgumentPosition pos | pos.isSelf()))
     }
 
-    predicate argumentHasImplicitBorrow(AstNode arg, BorrowKind borrow) {
-      exists(this.resolveCallTarget(_, "", borrow)) and
-      borrow != TNoBorrowKind() and
+    predicate argumentHasImplicitBorrow(AstNode arg, boolean isMutable) {
+      exists(this.resolveCallTarget(_, "", TSomeBorrowKind(isMutable))) and
       arg = this.getArg(any(ArgumentPosition pos | pos.isSelf()))
     }
   }
@@ -2010,24 +2016,22 @@ private module MethodResolution {
       result = super.getOperand(pos.asPosition() + 1)
     }
 
-    private predicate implicitBorrowAt(ArgumentPosition pos, BorrowKind borrow) {
+    private predicate implicitBorrowAt(ArgumentPosition pos, boolean isMutable) {
       exists(int borrows | super.isOverloaded(_, _, borrows) |
         pos.isSelf() and
         borrows >= 1 and
-        if this instanceof AssignmentOperation
-        then borrow = TMutBorrowKind()
-        else borrow = TSharedBorrowKind()
+        if this instanceof CompoundAssignmentExpr then isMutable = true else isMutable = false
         or
         pos.asPosition() = 0 and
         borrows = 2 and
-        borrow = TSharedBorrowKind()
+        isMutable = false
       )
     }
 
     override Type getArgumentTypeAt(ArgumentPosition pos, TypePath path) {
-      exists(BorrowKind borrow, RefType rt |
-        this.implicitBorrowAt(pos, borrow) and
-        rt = borrow.getRefType()
+      exists(boolean isMutable, RefType rt |
+        this.implicitBorrowAt(pos, isMutable) and
+        rt = getRefType(isMutable)
       |
         result = rt and
         path.isEmpty()
@@ -2042,9 +2046,9 @@ private module MethodResolution {
       result = inferType(this.getArg(pos), path)
     }
 
-    override predicate argumentHasImplicitBorrow(AstNode arg, BorrowKind borrow) {
+    override predicate argumentHasImplicitBorrow(AstNode arg, boolean isMutable) {
       exists(ArgumentPosition pos |
-        this.implicitBorrowAt(pos, borrow) and
+        this.implicitBorrowAt(pos, isMutable) and
         arg = this.getArg(pos)
       )
     }
@@ -2083,13 +2087,13 @@ private module MethodResolution {
     pragma[nomagic]
     predicate hasNoCompatibleNonBlanketTarget() {
       mc_.hasNoCompatibleNonBlanketTargetSharedBorrow(derefChain) and
-      borrow = TSharedBorrowKind()
+      borrow.isSharedBorrow()
       or
       mc_.hasNoCompatibleNonBlanketTargetMutBorrow(derefChain) and
-      borrow = TMutBorrowKind()
+      borrow.isMutableBorrow()
       or
       mc_.hasNoCompatibleNonBlanketTargetNoBorrow(derefChain) and
-      borrow = TNoBorrowKind()
+      borrow.isNoBorrow()
     }
 
     pragma[nomagic]
@@ -2391,7 +2395,7 @@ private module MethodCallMatchingInput implements MatchingWithEnvironmentInputSi
   class AccessEnvironment = string;
 
   bindingset[derefChain, borrow]
-  private AccessEnvironment encodeDerefChainBorrow(string derefChain, BorrowKind borrow) {
+  additional AccessEnvironment encodeDerefChainBorrow(string derefChain, BorrowKind borrow) {
     result = derefChain + ";" + borrow
   }
 
@@ -2437,7 +2441,7 @@ private module MethodCallMatchingInput implements MatchingWithEnvironmentInputSi
         or
         exists(TypePath suffix |
           result = inferType(this.getNodeAt(apos), suffix) and
-          path = TypePath::cons(getRefTypeParameter(), suffix)
+          path = TypePath::cons(getRefTypeParameter(_), suffix)
         )
       else (
         not apos.isSelf() and
@@ -2500,7 +2504,7 @@ private Type inferMethodCallType0(
       // the implicit deref
       apos.isReturn() and
       a instanceof IndexExpr
-    then path0.isCons(getRefTypeParameter(), path)
+    then path0.isCons(getRefTypeParameter(_), path)
     else path = path0
   )
 }
@@ -2523,13 +2527,13 @@ private Type inferMethodCallType1(AstNode n, boolean isReturn, TypePath path) {
     or
     // adjust for implicit deref
     apos.isSelf() and
-    derefChainBorrow = ".ref;" and
-    path = TypePath::cons(getRefTypeParameter(), path0)
+    derefChainBorrow = MethodCallMatchingInput::encodeDerefChainBorrow(".ref", TNoBorrowKind()) and
+    path = TypePath::cons(getRefTypeParameter(_), path0)
     or
     // adjust for implicit borrow
     apos.isSelf() and
-    derefChainBorrow = [";&", ";&mut"] and
-    path0.isCons(getRefTypeParameter(), path)
+    derefChainBorrow = MethodCallMatchingInput::encodeDerefChainBorrow("", TSomeBorrowKind(_)) and
+    path0.isCons(getRefTypeParameter(_), path)
   )
 }
 
@@ -3121,7 +3125,7 @@ private module OperationMatchingInput implements MatchingInputSig {
           this.borrowsAt(dpos)
           or
           dpos.isReturn() and this.derefsReturn()
-        then path0.isCons(getRefTypeParameter(), path)
+        then path0.isCons(getRefTypeParameter(_), path)
         else path0 = path
       )
     }
@@ -3274,9 +3278,9 @@ private module FieldExprMatchingInput implements MatchingInputSig {
         if apos.isSelf()
         then
           // adjust for implicit deref
-          path0.isCons(getRefTypeParameter(), path)
+          path0.isCons(getRefTypeParameter(_), path)
           or
-          not path0.isCons(getRefTypeParameter(), _) and
+          not path0.isCons(getRefTypeParameter(_), _) and
           not (result instanceof RefType and path0.isEmpty()) and
           path = path0
         else path = path0
@@ -3318,9 +3322,9 @@ private Type inferFieldExprType(AstNode n, TypePath path) {
         if receiverType instanceof RefType
         then
           // adjust for implicit deref
-          not path0.isCons(getRefTypeParameter(), _) and
+          not path0.isCons(getRefTypeParameter(_), _) and
           not (path0.isEmpty() and result instanceof RefType) and
-          path = TypePath::cons(getRefTypeParameter(), path0)
+          path = TypePath::cons(getRefTypeParameter(_), path0)
         else path = path0
       )
     else path = path0
@@ -3353,7 +3357,7 @@ private Type inferRefPatType(AstNode ref) {
     or
     ref = any(RefPat rp | if rp.isMut() then isMut = true else isMut = false)
   |
-    if isMut = true then result instanceof RefMutType else result instanceof RefSharedType
+    result = getRefType(isMut)
   )
 }
 
@@ -3410,7 +3414,7 @@ private Type inferLiteralType(LiteralExpr le, TypePath path, boolean certain) {
   (
     path.isEmpty() and result instanceof RefSharedType
     or
-    path = TypePath::singleton(getRefSharedTypeParameter()) and
+    path = TypePath::singleton(getRefTypeParameter(false)) and
     result = getStrStruct()
   ) and
   certain = true
@@ -3531,7 +3535,7 @@ private Type inferIndexExprType(IndexExpr ie, TypePath path) {
     exprPath.isCons(getArrayTypeParameter(), path)
     or
     exists(TypePath path0 |
-      exprPath.isCons(getRefTypeParameter(), path0) and
+      exprPath.isCons(getRefTypeParameter(_), path0) and
       path0.isCons(getSliceTypeParameter(), path)
     )
   )
@@ -3843,8 +3847,8 @@ private module Cached {
 
   /** Holds if `n` is implicitly borrowed. */
   cached
-  predicate implicitBorrow(AstNode n) {
-    any(MethodResolution::MethodCall mc).argumentHasImplicitBorrow(n, _)
+  predicate implicitBorrow(AstNode n, boolean isMutable) {
+    any(MethodResolution::MethodCall mc).argumentHasImplicitBorrow(n, isMutable)
   }
 
   /**