lapack/{gonum,testlapack}: apply semgrep-go suggestions (#1743)

lapack/gonum/dtrexc.go

@@ -174,12 +174,12 @@ func (impl Implementation) Dtrexc(compq lapack.UpdateSchurComp, n int, t []float
 		here := ifst
 		for here > ilst {
 			// Swap block with next one above.
+			nbnext := 1
+			if here >= 2 && t[(here-1)*ldt+here-2] != 0 {
+				nbnext = 2
+			}
 			if nbf == 1 || nbf == 2 {
 				// Current block either 1×1 or 2×2.
-				nbnext := 1
-				if here-2 >= 0 && t[(here-1)*ldt+here-2] != 0 {
-					nbnext = 2
-				}
 				ok = impl.Dlaexc(wantq, n, t, ldt, q, ldq, here-nbnext, nbnext, nbf, work)
 				if !ok {
 					return ifst, here, false
@@ -194,10 +194,6 @@ func (impl Implementation) Dtrexc(compq lapack.UpdateSchurComp, n int, t []float
 
 			// Current block consists of two 1×1 blocks each of
 			// which must be swapped individually.
-			nbnext := 1
-			if here-2 >= 0 && t[(here-1)*ldt+here-2] != 0 {
-				nbnext = 2
-			}
 			ok = impl.Dlaexc(wantq, n, t, ldt, q, ldq, here-nbnext, nbnext, 1, work)
 			if !ok {
 				return ifst, here, false

lapack/testlapack/dtrexc.go

@@ -175,7 +175,7 @@ func dtrexcTest(t *testing.T, impl Dtrexcer, rnd *rand.Rand, n, ifst, ilst, extr
 			if modMin <= j && j < modMax {
 				continue
 			}
-			if q.Data[i*q.Stride+j]-qCopy.Data[i*qCopy.Stride+j] != 0 {
+			if q.Data[i*q.Stride+j] != qCopy.Data[i*qCopy.Stride+j] {
 				t.Errorf("%v: unexpected modification of Q[%v,%v]", name, i, j)
 			}
 		}