[tools] gopls/internal/cache/parsego: construct File.Cursor lazily

[Alan Donovan (Gerrit)]

Alan Donovan submitted the change with unreviewed changes

Unreviewed changes

2 is the latest approved patch-set.
The change was submitted with unreviewed changes in the following files:

```
The name of the file: gopls/internal/golang/type_definition.go
Insertions: 1, Deletions: 1.

@@ -19,7 +19,7 @@
 )
 
 // TypeDefinition handles the textDocument/typeDefinition request for Go files.
-func TypeDefinition(ctx context.Context, snapshot *cache.Snapshot, fh file.Handle, position protocol.Position) ([]protocol.Location, error) {
+func TypeDefinition(ctx context.Context, snapshot *cache.Snapshot, fh file.Handle, rng protocol.Range) ([]protocol.Location, error) {
 	ctx, done := event.Start(ctx, "golang.TypeDefinition")
 	defer done()
 
@@ -27,11 +27,11 @@
 	if err != nil {
 		return nil, err
 	}
-	pos, err := pgf.PositionPos(position)
+	start, end, err := pgf.RangePos(rng)
 	if err != nil {
 		return nil, err
 	}
-	cur, ok := pgf.Cursor().FindByPos(pos, pos)
+	cur, ok := pgf.Cursor().FindByPos(start, end)
 	if !ok {
 		return nil, fmt.Errorf("no enclosing syntax") // can't happen
 	}
@@ -69,13 +69,19 @@
 	if t == nil {
 		return nil, fmt.Errorf("no enclosing expression has a type")
 	}
-	tname := typeToObject(t)
-	if tname == nil {
-		return nil, fmt.Errorf("cannot find type name from type %s", t)
+	tnames := typeToObjects(t)
+	if len(tnames) == 0 {
+		return nil, fmt.Errorf("cannot find type name(s) from type %s", t)
 	}
-	loc, err := ObjectLocation(ctx, pkg.FileSet(), snapshot, tname)
-	if err != nil {
-		return nil, err
+
+	var locs []protocol.Location
+	for _, t := range tnames {
+		loc, err := ObjectLocation(ctx, pkg.FileSet(), snapshot, t)
+		if err != nil {
+			return nil, err
+		}
+		locs = append(locs, loc)
 	}
-	return []protocol.Location{loc}, nil
+
+	return locs, nil
 }
```

Change information

Commit message:

gopls/internal/cache/parsego: construct File.Cursor lazily

File.Cursor is now an accessor method.

This crude benchmark shows a significant improvement in wall time:
$ /usr/bin/time GOPLSCACHE=$(mktemp -d) gopls check ./main.go
before 3.920 3.927 4.081 4.279 4.416 4.542 5.453 mean=4.374
after  3.710 3.758 3.820 3.881 3.942 4.199 4.378 mean=3.955
Unfortunately our perf dashboard is currently down (golang/go#76873).

Fixes golang/go#76813

Change-Id: I822e20206e39d63fccc8ed11ee1f3ba45eca07d8

Reviewed-on: https://go-review.googlesource.com/c/tools/+/730120

Reviewed-by: Madeline Kalil <mka...@google.com>

Auto-Submit: Alan Donovan <adon...@google.com>

Commit-Queue: Alan Donovan <adon...@google.com>

TryBot-Bypass: Alan Donovan <adon...@google.com>

Files:

• M gopls/internal/analysis/fillstruct/fillstruct.go
• M gopls/internal/cache/parsego/file.go
• M gopls/internal/cache/parsego/parse.go
• M gopls/internal/cache/xrefs/xrefs.go
• M gopls/internal/golang/call_hierarchy.go
• M gopls/internal/golang/codeaction.go
• M gopls/internal/golang/definition.go
• M gopls/internal/golang/extract.go
• M gopls/internal/golang/folding_range.go
• M gopls/internal/golang/hover.go
• M gopls/internal/golang/implementation.go
• M gopls/internal/golang/inlay_hint.go
• M gopls/internal/golang/inline.go
• M gopls/internal/golang/invertifcondition.go
• M gopls/internal/golang/lines.go
• M gopls/internal/golang/modify_tags.go
• M gopls/internal/golang/references.go
• M gopls/internal/golang/rename.go
• M gopls/internal/golang/rename_check.go
• M gopls/internal/golang/stubmethods/stubcalledfunc.go
• M gopls/internal/golang/stubmethods/stubmethods.go
• M gopls/internal/golang/type_definition.go
• M gopls/internal/golang/type_hierarchy.go
• M gopls/internal/golang/undeclared.go
• M gopls/internal/mcp/file_context.go
• M gopls/internal/server/link.go

Change size: M

Delta: 26 files changed, 65 insertions(+), 61 deletions(-)

Branch: refs/heads/master

Submit Requirements:

• Code-Review: +2 by Madeline Kalil
• TryBots-Pass: LUCI-TryBot-Result-1 by Go LUCI, TryBot-Bypass+1 by Alan Donovan

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Gerrit

Gerrit-MessageType: merged

Gerrit-Project: tools

Gerrit-Branch: master

Gerrit-Change-Id: I822e20206e39d63fccc8ed11ee1f3ba45eca07d8

Gerrit-Change-Number: 730120

Gerrit-PatchSet: 4

Gerrit-Owner: Alan Donovan <adon...@google.com>

Gerrit-Reviewer: Alan Donovan <adon...@google.com>

Gerrit-Reviewer: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>

Gerrit-Reviewer: Madeline Kalil <mka...@google.com>