gopls/internal/lsp/cache: guard against "unsafe" by package path, not ID

The crash in golang/go#60890 suggests that a user encountered a variant
of the unsafe package. I'm not sure how to reproduce this, but in any
case we should be checking package path, not ID, when guarding against
exporting "unsafe".

For golang/go#60890

Change-Id: Ib6c546b8f74ba513f5ee3df09b5ba29cea0c1b85
Reviewed-on: https://go-review.googlesource.com/c/tools/+/504555
Run-TryBot: Robert Findley <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
gopls-CI: kokoro <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>

Author: findleyr

gopls/internal/lsp/cache/check.go

@@ -453,6 +453,13 @@ func (b *typeCheckBatch) getImportPackage(ctx context.Context, id PackageID) (pk
 	}
 
 	ph := b.handles[id]
+
+	// Do a second check for "unsafe" defensively, due to golang/go#60890.
+	if ph.m.PkgPath == "unsafe" {
+		bug.Reportf("encountered \"unsafe\" as %s (golang/go#60890)", id)
+		return types.Unsafe, nil
+	}
+
 	data, err := filecache.Get(exportDataKind, ph.key)
 	if err == filecache.ErrNotFound {
 		// No cached export data: type-check as fast as possible.
@@ -632,13 +639,17 @@ func (b *typeCheckBatch) checkPackage(ctx context.Context, ph *packageHandle) (*
 				diagnosticsKind: encodeDiagnostics(pkg.diagnostics),
 			}
 
-			if ph.m.ID != "unsafe" { // unsafe cannot be exported
+			if ph.m.PkgPath != "unsafe" { // unsafe cannot be exported
 				exportData, err := gcimporter.IExportShallow(pkg.fset, pkg.types)
 				if err != nil {
 					bug.Reportf("exporting package %v: %v", ph.m.ID, err)
 				} else {
 					toCache[exportDataKind] = exportData
 				}
+			} else if ph.m.ID != "unsafe" {
+				// golang/go#60890: we should only ever see one variant of the "unsafe"
+				// package.
+				bug.Reportf("encountered \"unsafe\" as %s (golang/go#60890)", ph.m.ID)
 			}
 
 			for kind, data := range toCache {