Rust: Fix bad join

Before
```
Pipeline standard for TypeInference::MethodCallMatching::AccessConstraint::RelevantAccess.getTypeAt/1#dispred#e8abf748@ada3a07w was evaluated in 801 iterations totaling 31ms (delta sizes total: 182871).
           50151   ~1%    {4} r1 = SCAN TypeInference::MethodCallMatching::AccessConstraint::MkRelevantAccess#7a01048b#prev_delta OUTPUT In.0, In.2, In.3, In.4
           39574   ~0%    {5}    | JOIN WITH `TypeInference::MethodCallMatchingInput::Access.getInferredNonSelfType/2#dispred#b181cb0a#prev` ON FIRST 2 OUTPUT Lhs.3, Rhs.3, _, Lhs.2, Rhs.2
                          {3}    | REWRITE WITH Tmp.2 := "", Out.2 := InverseAppend(In.3,Tmp.2,In.4) KEEPING 3
           36996   ~0%    {3}    | SCAN OUTPUT In.0, In.2, In.1

        36102333   ~0%    {4} r2 = SCAN TypeInference::MethodCallMatching::AccessConstraint::MkRelevantAccess#7a01048b#prev OUTPUT In.0, In.2, In.3, In.4
           90175   ~1%    {5}    | JOIN WITH `TypeInference::MethodCallMatchingInput::Access.getInferredNonSelfType/2#dispred#b181cb0a#prev_delta` ON FIRST 2 OUTPUT Lhs.3, Rhs.3, _, Lhs.2, Rhs.2
                          {3}    | REWRITE WITH Tmp.2 := "", Out.2 := InverseAppend(In.3,Tmp.2,In.4) KEEPING 3
           65014   ~1%    {3}    | SCAN OUTPUT In.0, In.2, In.1

           50151   ~1%    {5} r3 = SCAN TypeInference::MethodCallMatching::AccessConstraint::MkRelevantAccess#7a01048b#prev_delta OUTPUT In.2, In.0, In.1, In.3, In.4
           24208   ~1%    {4}    | JOIN WITH `FunctionType::FunctionPosition.isSelf/0#dispred#9e84d302` ON FIRST 1 OUTPUT Lhs.1, Lhs.2, Lhs.3, Lhs.4
           95022   ~0%    {9}    | JOIN WITH `TypeInference::MethodCallMatchingInput::Access.getInferredSelfType/3#dispred#45b2f893#prev` ON FIRST 1 OUTPUT Lhs.2, Lhs.3, Rhs.2, Rhs.3, Rhs.4, _, Rhs.1, Lhs.1, _
                          {6}    | REWRITE WITH Tmp.5 := ";", Tmp.5 := (In.6 ++ Tmp.5), Tmp.8 := "", Out.5 := InverseAppend(Tmp.5,Tmp.8,In.7) KEEPING 6
           93919   ~1%    {7}    | SCAN OUTPUT In.0, In.1, In.2, In.3, In.4, In.5, _
                          {6}    | REWRITE WITH NOT [NOT [Tmp.6 := "borrow", TEST InOut.5 = Tmp.6, Tmp.6 := true, TEST InOut.2 = Tmp.6], NOT [Tmp.6 := "", TEST InOut.5 = Tmp.6, Tmp.6 := true, TEST InOut.2 != Tmp.6]] KEEPING 6
           81298   ~1%    {5}    | SCAN OUTPUT In.1, In.4, _, In.0, In.3
                          {3}    | REWRITE WITH Tmp.2 := "", Out.2 := InverseAppend(In.3,Tmp.2,In.4) KEEPING 3
           64110   ~1%    {3}    | SCAN OUTPUT In.0, In.2, In.1

        36102333   ~0%    {5} r4 = SCAN TypeInference::MethodCallMatching::AccessConstraint::MkRelevantAccess#7a01048b#prev OUTPUT In.2, In.0, In.1, In.3, In.4
        17473531   ~0%    {4}    | JOIN WITH `FunctionType::FunctionPosition.isSelf/0#dispred#9e84d302` ON FIRST 1 OUTPUT Lhs.1, Lhs.2, Lhs.3, Lhs.4
           47409   ~1%    {9}    | JOIN WITH `TypeInference::MethodCallMatchingInput::Access.getInferredSelfType/3#dispred#45b2f893#prev_delta` ON FIRST 1 OUTPUT Lhs.2, Lhs.3, Rhs.2, Rhs.3, Rhs.4, _, Rhs.1, Lhs.1, _
                          {6}    | REWRITE WITH Tmp.5 := ";", Tmp.5 := (In.6 ++ Tmp.5), Tmp.8 := "", Out.5 := InverseAppend(Tmp.5,Tmp.8,In.7) KEEPING 6
           29885   ~0%    {7}    | SCAN OUTPUT In.0, In.1, In.2, In.3, In.4, In.5, _
                          {6}    | REWRITE WITH NOT [NOT [Tmp.6 := "borrow", TEST InOut.5 = Tmp.6, Tmp.6 := true, TEST InOut.2 = Tmp.6], NOT [Tmp.6 := "", TEST InOut.5 = Tmp.6, Tmp.6 := true, TEST InOut.2 != Tmp.6]] KEEPING 6
           16952   ~1%    {5}    | SCAN OUTPUT In.1, In.4, _, In.0, In.3
                          {3}    | REWRITE WITH Tmp.2 := "", Out.2 := InverseAppend(In.3,Tmp.2,In.4) KEEPING 3
           16829   ~0%    {3}    | SCAN OUTPUT In.0, In.2, In.1

          182949   ~1%    {3} r5 = r1 UNION r2 UNION r3 UNION r4
          182949   ~1%    {3}    | AND NOT `TypeInference::MethodCallMatching::AccessConstraint::RelevantAccess.getTypeAt/1#dispred#e8abf748#prev`(FIRST 3)
                          return r5
```

After
```
Pipeline standard for TypeInference::MethodCallMatching::AccessConstraint::RelevantAccess.getTypeAt/1#dispred#e8abf748@31ee547w was evaluated in 801 iterations totaling 19ms (delta sizes total: 182946).
         81298   ~0%    {5} r1 = JOIN TypeInference::MethodCallMatching::AccessConstraint::MkRelevantAccess#7a01048b#prev_delta WITH `TypeInference::MethodCallMatchingInput::Access.getInferredSelfType/3#dispred#45b2f893#prev` ON FIRST 3 OUTPUT Lhs.4, Rhs.4, _, Lhs.3, Rhs.3
                        {3}    | REWRITE WITH Tmp.2 := "", Out.2 := InverseAppend(In.3,Tmp.2,In.4) KEEPING 3
         64110   ~1%    {3}    | SCAN OUTPUT In.0, In.2, In.1

         39574   ~0%    {5} r2 = JOIN TypeInference::MethodCallMatching::AccessConstraint::MkRelevantAccess#7a01048b#prev_delta WITH `TypeInference::MethodCallMatchingInput::Access.getInferredNonSelfType/2#dispred#b181cb0a#prev` ON FIRST 2 OUTPUT Lhs.4, Rhs.3, _, Lhs.3, Rhs.2
                        {3}    | REWRITE WITH Tmp.2 := "", Out.2 := InverseAppend(In.3,Tmp.2,In.4) KEEPING 3
         36996   ~0%    {3}    | SCAN OUTPUT In.0, In.2, In.1

         16952   ~0%    {5} r3 = JOIN TypeInference::MethodCallMatching::AccessConstraint::MkRelevantAccess#7a01048b#prev WITH `TypeInference::MethodCallMatchingInput::Access.getInferredSelfType/3#dispred#45b2f893#prev_delta` ON FIRST 3 OUTPUT Lhs.4, Rhs.4, _, Lhs.3, Rhs.3
                        {3}    | REWRITE WITH Tmp.2 := "", Out.2 := InverseAppend(In.3,Tmp.2,In.4) KEEPING 3
         16829   ~0%    {3}    | SCAN OUTPUT In.0, In.2, In.1

         90175   ~0%    {5} r4 = JOIN TypeInference::MethodCallMatching::AccessConstraint::MkRelevantAccess#7a01048b#prev WITH `TypeInference::MethodCallMatchingInput::Access.getInferredNonSelfType/2#dispred#b181cb0a#prev_delta` ON FIRST 2 OUTPUT Lhs.4, Rhs.3, _, Lhs.3, Rhs.2
                        {3}    | REWRITE WITH Tmp.2 := "", Out.2 := InverseAppend(In.3,Tmp.2,In.4) KEEPING 3
         65014   ~0%    {3}    | SCAN OUTPUT In.0, In.2, In.1

        182949   ~1%    {3} r5 = r1 UNION r2 UNION r3 UNION r4
        182949   ~1%    {3}    | AND NOT `TypeInference::MethodCallMatching::AccessConstraint::RelevantAccess.getTypeAt/1#dispred#e8abf748#prev`(FIRST 3)
                        return r5
```

Author: hvitved

rust/ql/lib/codeql/rust/internal/TypeInference.qll

@@ -1812,8 +1812,12 @@ private module MethodCallMatchingInput implements MatchingWithEnvironmentInputSi
     }
 
     pragma[nomagic]
-    private Type getInferredSelfType(string derefChain, boolean borrow, TypePath path) {
-      result = this.getACandidateReceiverTypeAt(derefChain, borrow, path)
+    private Type getInferredSelfType(AccessPosition apos, string derefChainBorrow, TypePath path) {
+      exists(string derefChain, boolean borrow |
+        result = this.getACandidateReceiverTypeAt(derefChain, borrow, path) and
+        derefChainBorrow = encodeDerefChainBorrow(derefChain, borrow) and
+        apos.isSelf()
+      )
     }
 
     pragma[nomagic]
@@ -1839,11 +1843,7 @@ private module MethodCallMatchingInput implements MatchingWithEnvironmentInputSi
 
     bindingset[derefChainBorrow]
     Type getInferredType(string derefChainBorrow, AccessPosition apos, TypePath path) {
-      exists(string derefChain, boolean borrow |
-        derefChainBorrow = encodeDerefChainBorrow(derefChain, borrow) and
-        apos.isSelf() and
-        result = this.getInferredSelfType(derefChain, borrow, path)
-      )
+      result = this.getInferredSelfType(apos, derefChainBorrow, path)
       or
       result = this.getInferredNonSelfType(apos, path)
     }

shared/typeinference/codeql/typeinference/internal/TypeInference.qll

@@ -1269,7 +1269,7 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
         }
 
         private newtype TRelevantAccess =
-          MkRelevantAccess(Access a, AccessEnvironment e, AccessPosition apos, TypePath path) {
+          MkRelevantAccess(Access a, AccessPosition apos, AccessEnvironment e, TypePath path) {
             relevantAccessConstraint(a, e, _, apos, path, _)
           }
 
@@ -1279,11 +1279,11 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
          */
         private class RelevantAccess extends MkRelevantAccess {
           Access a;
-          AccessEnvironment e;
           AccessPosition apos;
+          AccessEnvironment e;
           TypePath path;
 
-          RelevantAccess() { this = MkRelevantAccess(a, e, apos, path) }
+          RelevantAccess() { this = MkRelevantAccess(a, apos, e, path) }
 
           Type getTypeAt(TypePath suffix) {
             result = a.getInferredType(e, apos, path.appendInverse(suffix))
@@ -1314,7 +1314,7 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
           Type constraint, TypePath path, Type t
         ) {
           exists(RelevantAccess ra |
-            ra = MkRelevantAccess(a, e, apos, prefix) and
+            ra = MkRelevantAccess(a, apos, e, prefix) and
             SatisfiesConstraint<RelevantAccess, SatisfiesConstraintInput>::satisfiesConstraintType(ra,
               constraint, path, t) and
             constraint = ra.getConstraint(target)