Comment improvements.  Put ALWAYS and NEVER macros on three unreachable
branches.

FossilOrigin-Name: 397617009e07004596476d6f5644fdf84c376f54
diff --git a/src/expr.c b/src/expr.c
index 982605d..f067079 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -2443,9 +2443,9 @@
         ExprList *pEList = pSelect->pEList;
 
         assert( !isRowid );
-        if( pEList->nExpr!=nVal ){
-          sqlite3SubselectError(pParse, pEList->nExpr, nVal);
-        }else{
+        /* If the LHS and RHS of the IN operator do not match, that
+        ** error will have been caught long before we reach this point. */
+        if( ALWAYS(pEList->nExpr==nVal) ){
           SelectDest dest;
           int i;
           sqlite3SelectDestInit(&dest, SRT_Set, pExpr->iTable);
diff --git a/src/where.c b/src/where.c
index 30854ee..74da408 100644
--- a/src/where.c
+++ b/src/where.c
@@ -2224,7 +2224,11 @@
 ** this case is 3.
 */
 int whereRangeVectorLen(
-  Parse *pParse, int iCur, Index *pIdx, int nEq, WhereTerm *pTerm
+  Parse *pParse,       /* Parsing context */
+  int iCur,            /* Cursor open on pIdx */
+  Index *pIdx,         /* The index to be used for a inequality constraint */
+  int nEq,             /* Number of prior equality constraints on same index */
+  WhereTerm *pTerm     /* The vector inequality constraint */
 ){
   int nCmp = sqlite3ExprVectorSize(pTerm->pExpr->pLeft);
   int i;
@@ -2261,7 +2265,8 @@
     if( aff!=idxaff ) break;
 
     pColl = sqlite3BinaryCompareCollSeq(pParse, pLhs, pRhs);
-    if( pColl==0 || sqlite3StrICmp(pColl->zName, pIdx->azColl[i+nEq]) ) break;
+    if( NEVER(pColl==0) ) break;
+    if( sqlite3StrICmp(pColl->zName, pIdx->azColl[i+nEq]) ) break;
   }
   return i;
 }
@@ -3573,7 +3578,11 @@
               isOrderDistinct = 0;
             }
             continue;  
-          }else if( eOp & WO_IN ){
+          }else if( ALWAYS(eOp & WO_IN) ){
+            /* ALWAYS() justification: eOp is an equality operator due to the
+            ** j<pLoop->u.btree.nEq constraint above.  Any equality other
+            ** than WO_IN is captured by the previous "if".  So this one
+            ** always has to be WO_IN. */
             Expr *pX = pLoop->aLTerm[j]->pExpr;
             for(i=j+1; i<pLoop->u.btree.nEq; i++){
               if( pLoop->aLTerm[i]->pExpr==pX ){
diff --git a/src/whereexpr.c b/src/whereexpr.c
index 823a2df..0032898 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -846,7 +846,9 @@
   ** inequality constraint (>, <, >= or <=), perform the processing 
   ** on the first element of the vector.  */
   assert( TK_GT+1==TK_LE && TK_GT+2==TK_LT && TK_GT+3==TK_GE );
-  if( pExpr->op==TK_VECTOR && (op>=TK_GT && op<=TK_GE) ){
+  assert( TK_IS<TK_GE && TK_ISNULL<TK_GE && TK_IN<TK_GE );
+  assert( op<=TK_GE );
+  if( pExpr->op==TK_VECTOR && (op>=TK_GT && ALWAYS(op<=TK_GE)) ){
     pExpr = pExpr->x.pList->a[0].pExpr;
   }