gopls/internal/lsp/source: enable new defers analyzer

This change enables the new defers analyzer in gopls.
It also adds it to the vet compatibility test.
A follow-up change will add it to vet itself.

Also, remove stray backquote in doc comment.

Updates golang/go#60048

Change-Id: I42f09bb79fcbe4e48593dd32fd066ddd39b9626f
Reviewed-on: https://go-review.googlesource.com/c/tools/+/502975
Run-TryBot: Alan Donovan <adonovan@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

Author: adonovan

go/analysis/passes/defers/doc.go

@@ -21,5 +21,5 @@
 //
 // The correct code is:
 //
-//	defer func() { recordLatency(time.Since(start)) }()`
+//	defer func() { recordLatency(time.Since(start)) }()
 package defers

go/analysis/unitchecker/vet_std_test.go

@@ -19,6 +19,7 @@ import (
 	"golang.org/x/tools/go/analysis/passes/cgocall"
 	"golang.org/x/tools/go/analysis/passes/composite"
 	"golang.org/x/tools/go/analysis/passes/copylock"
+	"golang.org/x/tools/go/analysis/passes/defers"
 	"golang.org/x/tools/go/analysis/passes/directive"
 	"golang.org/x/tools/go/analysis/passes/errorsas"
 	"golang.org/x/tools/go/analysis/passes/framepointer"
@@ -54,6 +55,7 @@ func vet() {
 		cgocall.Analyzer,
 		composite.Analyzer,
 		copylock.Analyzer,
+		defers.Analyzer,
 		directive.Analyzer,
 		errorsas.Analyzer,
 		framepointer.Analyzer,
@@ -68,8 +70,8 @@ func vet() {
 		stdmethods.Analyzer,
 		stringintconv.Analyzer,
 		structtag.Analyzer,
-		tests.Analyzer,
 		testinggoroutine.Analyzer,
+		tests.Analyzer,
 		timeformat.Analyzer,
 		unmarshal.Analyzer,
 		unreachable.Analyzer,

gopls/doc/analyzers.md

@@ -108,6 +108,26 @@ errors is discouraged.
 
 **Enabled by default.**
 
+## **defer**
+
+report common mistakes in defer statements
+
+The defer analyzer reports a diagnostic when a defer statement would
+result in a non-deferred call to time.Since, as experience has shown
+that this is nearly always a mistake.
+
+For example:
+
+	start := time.Now()
+	...
+	defer recordLatency(time.Since(start)) // error: call to time.Since is not deferred
+
+The correct code is:
+
+	defer func() { recordLatency(time.Since(start)) }()
+
+**Enabled by default.**
+
 ## **deprecated**
 
 check for use of deprecated identifiers

gopls/doc/generate_test.go

@@ -23,6 +23,6 @@ func TestGenerated(t *testing.T) {
 		t.Fatal(err)
 	}
 	if !ok {
-		t.Error("documentation needs updating. run: `go run doc/generate.go` from the gopls module.")
+		t.Error("documentation needs updating. Run: cd gopls && go generate ./doc")
 	}
 }

gopls/internal/lsp/source/api_json.go

@@ -26,6 +26,7 @@ import (
 	"golang.org/x/tools/go/analysis/passes/composite"
 	"golang.org/x/tools/go/analysis/passes/copylock"
 	"golang.org/x/tools/go/analysis/passes/deepequalerrors"
+	"golang.org/x/tools/go/analysis/passes/defers"
 	"golang.org/x/tools/go/analysis/passes/directive"
 	"golang.org/x/tools/go/analysis/passes/errorsas"
 	"golang.org/x/tools/go/analysis/passes/fieldalignment"
@@ -1544,6 +1545,7 @@ func defaultAnalyzers() map[string]*Analyzer {
 		cgocall.Analyzer.Name:       {Analyzer: cgocall.Analyzer, Enabled: true},
 		composite.Analyzer.Name:     {Analyzer: composite.Analyzer, Enabled: true},
 		copylock.Analyzer.Name:      {Analyzer: copylock.Analyzer, Enabled: true},
+		defers.Analyzer.Name:        {Analyzer: defers.Analyzer, Enabled: true},
 		deprecated.Analyzer.Name:    {Analyzer: deprecated.Analyzer, Enabled: true, Severity: protocol.SeverityHint, Tag: []protocol.DiagnosticTag{protocol.Deprecated}},
 		directive.Analyzer.Name:     {Analyzer: directive.Analyzer, Enabled: true},
 		errorsas.Analyzer.Name:      {Analyzer: errorsas.Analyzer, Enabled: true},