Fix shadowed variable in faiss/impl/index_write.cpp

Summary:
Our upcoming compiler upgrade will require us not to have shadowed variables. Such variables have a _high_ bug rate and reduce readability, so we would like to avoid them even if the compiler was not forcing us to do so.

This codemod attempts to fix an instance of a shadowed variable. Please review with care: if it's failed the result will be a silent bug.

**What's a shadowed variable?**

Shadowed variables are variables in an inner scope with the same name as another variable in an outer scope. Having the same name for both variables might be semantically correct, but it can make the code confusing to read! It can also hide subtle bugs.

This diff fixes such an issue by renaming the variable.

 - If you approve of this diff, please use the "Accept & Ship" button :-)

Reviewed By: meyering

Differential Revision: D52582916

fbshipit-source-id: 367ea85b569063efa50c82702c3ba5efa2fb92f9

Author: r-barnes

faiss/impl/index_write.cpp

@@ -433,13 +433,14 @@ void write_index(const Index* idx, IOWriter* f) {
         WRITE1(idxr->code_size);
         WRITEVECTOR(idxr->codes);
     } else if (
-            auto* idxr = dynamic_cast<const IndexLocalSearchQuantizer*>(idx)) {
+            auto* idxr_2 =
+                    dynamic_cast<const IndexLocalSearchQuantizer*>(idx)) {
         uint32_t h = fourcc("IxLS");
         WRITE1(h);
         write_index_header(idx, f);
-        write_LocalSearchQuantizer(&idxr->lsq, f);
-        WRITE1(idxr->code_size);
-        WRITEVECTOR(idxr->codes);
+        write_LocalSearchQuantizer(&idxr_2->lsq, f);
+        WRITE1(idxr_2->code_size);
+        WRITEVECTOR(idxr_2->codes);
     } else if (
             const IndexProductResidualQuantizer* idxpr =
                     dynamic_cast<const IndexProductResidualQuantizer*>(idx)) {
@@ -572,26 +573,26 @@ void write_index(const Index* idx, IOWriter* f) {
 
         write_InvertedLists(ivaqfs->invlists, f);
     } else if (
-            const ResidualCoarseQuantizer* idxr =
+            const ResidualCoarseQuantizer* idxr_2 =
                     dynamic_cast<const ResidualCoarseQuantizer*>(idx)) {
         uint32_t h = fourcc("ImRQ");
         WRITE1(h);
         write_index_header(idx, f);
-        write_ResidualQuantizer(&idxr->rq, f);
-        WRITE1(idxr->beam_factor);
+        write_ResidualQuantizer(&idxr_2->rq, f);
+        WRITE1(idxr_2->beam_factor);
     } else if (
-            const Index2Layer* idxp = dynamic_cast<const Index2Layer*>(idx)) {
+            const Index2Layer* idxp_2 = dynamic_cast<const Index2Layer*>(idx)) {
         uint32_t h = fourcc("Ix2L");
         WRITE1(h);
         write_index_header(idx, f);
-        write_index(idxp->q1.quantizer, f);
-        WRITE1(idxp->q1.nlist);
-        WRITE1(idxp->q1.quantizer_trains_alone);
-        write_ProductQuantizer(&idxp->pq, f);
-        WRITE1(idxp->code_size_1);
-        WRITE1(idxp->code_size_2);
-        WRITE1(idxp->code_size);
-        WRITEVECTOR(idxp->codes);
+        write_index(idxp_2->q1.quantizer, f);
+        WRITE1(idxp_2->q1.nlist);
+        WRITE1(idxp_2->q1.quantizer_trains_alone);
+        write_ProductQuantizer(&idxp_2->pq, f);
+        WRITE1(idxp_2->code_size_1);
+        WRITE1(idxp_2->code_size_2);
+        WRITE1(idxp_2->code_size);
+        WRITEVECTOR(idxp_2->codes);
     } else if (
             const IndexScalarQuantizer* idxs =
                     dynamic_cast<const IndexScalarQuantizer*>(idx)) {
@@ -601,15 +602,16 @@ void write_index(const Index* idx, IOWriter* f) {
         write_ScalarQuantizer(&idxs->sq, f);
         WRITEVECTOR(idxs->codes);
     } else if (
-            const IndexLattice* idxl = dynamic_cast<const IndexLattice*>(idx)) {
+            const IndexLattice* idxl_2 =
+                    dynamic_cast<const IndexLattice*>(idx)) {
         uint32_t h = fourcc("IxLa");
         WRITE1(h);
-        WRITE1(idxl->d);
-        WRITE1(idxl->nsq);
-        WRITE1(idxl->scale_nbit);
-        WRITE1(idxl->zn_sphere_codec.r2);
+        WRITE1(idxl_2->d);
+        WRITE1(idxl_2->nsq);
+        WRITE1(idxl_2->scale_nbit);
+        WRITE1(idxl_2->zn_sphere_codec.r2);
         write_index_header(idx, f);
-        WRITEVECTOR(idxl->trained);
+        WRITEVECTOR(idxl_2->trained);
     } else if (
             const IndexIVFFlatDedup* ivfl =
                     dynamic_cast<const IndexIVFFlatDedup*>(idx)) {
@@ -628,11 +630,12 @@ void write_index(const Index* idx, IOWriter* f) {
         }
         write_InvertedLists(ivfl->invlists, f);
     } else if (
-            const IndexIVFFlat* ivfl = dynamic_cast<const IndexIVFFlat*>(idx)) {
+            const IndexIVFFlat* ivfl_2 =
+                    dynamic_cast<const IndexIVFFlat*>(idx)) {
         uint32_t h = fourcc("IwFl");
         WRITE1(h);
-        write_ivf_header(ivfl, f);
-        write_InvertedLists(ivfl->invlists, f);
+        write_ivf_header(ivfl_2, f);
+        write_InvertedLists(ivfl_2->invlists, f);
     } else if (
             const IndexIVFScalarQuantizer* ivsc =
                     dynamic_cast<const IndexIVFScalarQuantizer*>(idx)) {
@@ -806,19 +809,19 @@ void write_index(const Index* idx, IOWriter* f) {
         WRITE1(idxpqfs->M2);
         WRITEVECTOR(idxpqfs->codes);
     } else if (
-            const IndexIVFPQFastScan* ivpq =
+            const IndexIVFPQFastScan* ivpq_2 =
                     dynamic_cast<const IndexIVFPQFastScan*>(idx)) {
         uint32_t h = fourcc("IwPf");
         WRITE1(h);
-        write_ivf_header(ivpq, f);
-        WRITE1(ivpq->by_residual);
-        WRITE1(ivpq->code_size);
-        WRITE1(ivpq->bbs);
-        WRITE1(ivpq->M2);
-        WRITE1(ivpq->implem);
-        WRITE1(ivpq->qbs2);
-        write_ProductQuantizer(&ivpq->pq, f);
-        write_InvertedLists(ivpq->invlists, f);
+        write_ivf_header(ivpq_2, f);
+        WRITE1(ivpq_2->by_residual);
+        WRITE1(ivpq_2->code_size);
+        WRITE1(ivpq_2->bbs);
+        WRITE1(ivpq_2->M2);
+        WRITE1(ivpq_2->implem);
+        WRITE1(ivpq_2->qbs2);
+        write_ProductQuantizer(&ivpq_2->pq, f);
+        write_InvertedLists(ivpq_2->invlists, f);
     } else if (
             const IndexRowwiseMinMax* imm =
                     dynamic_cast<const IndexRowwiseMinMax*>(idx)) {
@@ -828,13 +831,13 @@ void write_index(const Index* idx, IOWriter* f) {
         write_index_header(imm, f);
         write_index(imm->index, f);
     } else if (
-            const IndexRowwiseMinMaxFP16* imm =
+            const IndexRowwiseMinMaxFP16* imm_2 =
                     dynamic_cast<const IndexRowwiseMinMaxFP16*>(idx)) {
         // IndexRowwiseMinmaxHalf
         uint32_t h = fourcc("IRMh");
         WRITE1(h);
-        write_index_header(imm, f);
-        write_index(imm->index, f);
+        write_index_header(imm_2, f);
+        write_index(imm_2->index, f);
     } else {
         FAISS_THROW_MSG("don't know how to serialize this type of index");
     }