fmt.Fprintf(&sb, "var _cgo%d %s = %s; ", i,
				gofmtLine(ptype), gofmtPos(arg, origArg.Pos()))
			continue
		}

		// Check for &a[i].
		if p.checkIndex(&sb, &sbCheck, arg, i) {
			continue
		}

		// Check for &x.
		if p.checkAddr(&sb, &sbCheck, arg, i) {
			continue
		}

		// Check for a[:].
		if p.checkSlice(&sb, &sbCheck, arg, i) {
			continue
		}

		if f == nil && fb == nil {
			continue
		}
		var actual string
		if f != nil {
			actual = string(f([]byte(tc.in), tc.arg))
		} else {
			actual = string(fb([]byte(tc.in), []byte(tc.arg)))
		}
		if actual != tc.out {
			t.Errorf("%s(%q, %q) = %q; want %q", name, tc.in, tc.arg, actual, tc.out)
		}
	}

	for _, tc := range trimNilTests {
		name := tc.f
		f, fb := toFn(name)