go/packages: fix precedence typo in needtypes calculation

I haven't figured out exactly how to exercise it,
but the code as written is clearly wrong.

Change-Id: I8849bc37210d08ad8ae3bc857a84ae55b34908a5
Reviewed-on: https://go-review.googlesource.com/c/tools/+/310511
Reviewed-by: Austin Clements <[email protected]>
Trust: Russ Cox <[email protected]>
Run-TryBot: Russ Cox <[email protected]>
Auto-Submit: Russ Cox <[email protected]>
gopls-CI: kokoro <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: rsc

go/packages/packages.go

@@ -634,7 +634,7 @@ func (ld *loader) refine(roots []string, list ...*Package) ([]*Package, error) {
 		needsrc := ((ld.Mode&(NeedSyntax|NeedTypesInfo) != 0 && (rootIndex >= 0 || ld.Mode&NeedDeps != 0)) ||
 			// ... or if we need types and the exportData is invalid. We fall back to (incompletely)
 			// typechecking packages from source if they fail to compile.
-			(ld.Mode&NeedTypes|NeedTypesInfo != 0 && exportDataInvalid)) && pkg.PkgPath != "unsafe"
+			(ld.Mode&(NeedTypes|NeedTypesInfo) != 0 && exportDataInvalid)) && pkg.PkgPath != "unsafe"
 		lpkg := &loaderPackage{
 			Package:   pkg,
 			needtypes: needtypes,