cue/load: clean up allTags

It was a remnant of this refactor and hasn't been used since:
https://cue-review.googlesource.com/c/cue/+/7901

Originally (before that CL) the Instance.AllTags field was populated
from //+build comments, something that's never been a supported thing in
CUE. It seems like it was a remnant of the original Go code this was
derived from.

Since that CL, the `AllTags` field has always remained empty and never
populated.

Signed-off-by: Roger Peppe <[email protected]>
Change-Id: I2a90c720ff567bd4eed7cec21f7a980654600cd2
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1197523
Reviewed-by: Paul Jolly <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>

cue/build/instance.go

@@ -97,6 +97,8 @@ type Instance struct {
 
 	// AllTags are the build tags that can influence file selection in this
 	// directory.
+	//
+	// Deprecated: this field is not used.
 	AllTags []string `api:"alpha"`
 
 	// Incomplete reports whether any dependencies had an error.

cue/load/loader_common.go

@@ -102,7 +102,6 @@ type fileProcessor struct {
 	firstFile        string
 	firstCommentFile string
 	imported         map[string][]token.Pos
-	allTags          map[string]bool
 	ignoreOther      bool // ignore files from other packages
 	allPackages      bool
 
@@ -119,7 +118,6 @@ type fileProcessorConfig = Config
 func newFileProcessor(c *fileProcessorConfig, p *build.Instance, tg *tagger) *fileProcessor {
 	return &fileProcessor{
 		imported: make(map[string][]token.Pos),
-		allTags:  make(map[string]bool),
 		c:        c,
 		pkgs:     map[string]*build.Instance{"_": p},
 		pkg:      p,
@@ -151,11 +149,6 @@ func (fp *fileProcessor) finalize(p *build.Instance) errors.Error {
 		return fp.err
 	}
 
-	for tag := range fp.allTags {
-		p.AllTags = append(p.AllTags, tag)
-	}
-	sort.Strings(p.AllTags)
-
 	p.ImportPaths, _ = cleanImports(fp.imported)
 
 	return nil
@@ -187,7 +180,7 @@ func (fp *fileProcessor) add(root string, file *build.File, mode importMode) (ad
 		return badFile(errors.Promote(err, ""))
 	}
 
-	match, data, err := matchFile(fp.c, file, true, fp.allTags, mode)
+	match, data, err := matchFile(fp.c, file, true, mode)
 	switch {
 	case match:
 

cue/load/match.go

@@ -47,9 +47,7 @@ func (e excludeError) Is(err error) bool { return err == errExclude }
 // If returnImports is true and name denotes a CUE file, matchFile reads
 // until the end of the imports (and returns that data) even though it only
 // considers text until the first non-comment.
-// If allTags is non-nil, matchFile records any encountered build tag
-// by setting allTags[tag] = true.
-func matchFile(cfg *Config, file *build.File, returnImports bool, allTags map[string]bool, mode importMode) (match bool, data []byte, err errors.Error) {
+func matchFile(cfg *Config, file *build.File, returnImports bool, mode importMode) (match bool, data []byte, err errors.Error) {
 	// Note: file.Source should already have been set by setFileSource just
 	// after the build.File value was created.
 	if file.Encoding != build.CUE {