update the report package

experimental/report/diagnostic.go

@@ -16,8 +16,6 @@ package report
 
 import (
 	"fmt"
-
-	"github.com/bufbuild/protocompile/experimental/internal"
 )
 
 // Level represents the severity of a diagnostic message.
@@ -128,8 +126,7 @@ func InFile(path string) DiagnosticOption {
 // The first annotation added is the "primary" annotation, and will be rendered
 // differently from the others.
 //
-// If at is nil (be it a nil interface, or a value that has a Nil() function
-// that returns true), or returns a nil span, this function will return nil.
+// If at is nil or returns the nil span, the returned DiagnosticOption is a no-op.
 func Snippet(at Spanner) DiagnosticOption {
 	return Snippetf(at, "")
 }
@@ -142,20 +139,10 @@ func Snippet(at Spanner) DiagnosticOption {
 // The first annotation added is the "primary" annotation, and will be rendered
 // differently from the others.
 //
-// If at is nil (be it a nil interface, or a value that has a Nil() function
-// that returns true), or returns a nil span, this function will return nil.
+// If at is nil or returns the nil span, the returned DiagnosticOption is a no-op.
 func Snippetf(at Spanner, format string, args ...any) DiagnosticOption {
-	if internal.Nil(at) {
-		return nil
-	}
-
-	span := at.Span()
-	if span.Nil() {
-		return nil
-	}
-
 	return snippet{
-		Span:    span,
+		Span:    getSpan(at),
 		message: fmt.Sprintf(format, args...),
 	}
 }
@@ -201,6 +188,10 @@ type snippet struct {
 }
 
 func (a snippet) apply(d *Diagnostic) {
+	if a.Span.Nil() {
+		return
+	}
+
 	a.primary = len(d.snippets) == 0
 	d.snippets = append(d.snippets, a)
 }

experimental/report/span.go

@@ -21,18 +21,27 @@ import (
 	"strings"
 	"sync"
 	"unicode"
-
-	"github.com/bufbuild/protocompile/experimental/internal"
 )
 
 // TabstopWidth is the size we render all tabstops as.
 const TabstopWidth int = 4
 
-// Spanner is any type with a span.
+// Spanner is any type with a [Span].
 type Spanner interface {
+	// Should return the zero [Span] to indicate that it does not contribute
+	// span information.
 	Span() Span
 }
 
+// getSpan extracts a span from a Spanner, but returns the nil span when
+// s is nil, which would otherwise panic.
+func getSpan(s Spanner) Span {
+	if s == nil {
+		return Span{}
+	}
+	return s.Span()
+}
+
 // Span is a location within a [File].
 type Span struct {
 	// The file this span refers to. The file must be indexed, since we plan to
@@ -85,16 +94,12 @@ func (s Span) String() string {
 func Join(spans ...Spanner) Span {
 	joined := Span{Start: math.MaxInt}
 	for _, span := range spans {
-		if internal.Nil(span) {
-			continue
-		}
-
-		span := span.Span()
-		if span.File == nil {
+		span := getSpan(span)
+		if span.Nil() {
 			continue
 		}
 
-		if joined.File == nil {
+		if joined.Nil() {
 			joined.File = span.File
 		} else if joined.File != span.File {
 			panic(fmt.Sprintf(