refactor(goldmark): finish the fieldorder dedup, share assertOwnFieldsPointersBeforeScalars

Round-2 code review flagged that the earlier fieldorder extraction
only moved isPointerish (the smaller helper) into the shared package,
leaving assertOwnFieldsPointersBeforeScalars duplicated verbatim in
both pkg/goldmark/ast/structlayout_test.go and
pkg/goldmark/parser/structlayout_test.go -- and the two copies had
already drifted (one carried an extra comment sentence the other
lacked), which is exactly the divergence sharing code is meant to
prevent. Move it into fieldorder as AssertPointersBeforeScalars(t
testing.TB, ...).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LJTrn4DizYTMdYj4tbswVJ

Author: claude

pkg/goldmark/ast/structlayout_test.go

@@ -10,31 +10,10 @@ import (
 	"testing"
 
 	"github.com/jeduden/mdsmith/pkg/goldmark/internal/fieldorder"
-	"github.com/stretchr/testify/assert"
 )
 
-// assertOwnFieldsPointersBeforeScalars checks that, among typ's
-// fields starting at index skip (use 1 to skip an embedded base
-// struct), no scalar (non-pointerish) field is followed by a
-// pointerish one.
-func assertOwnFieldsPointersBeforeScalars(t *testing.T, typ reflect.Type, skip int) {
-	t.Helper()
-	seenScalar := false
-	for i := skip; i < typ.NumField(); i++ {
-		f := typ.Field(i)
-		if fieldorder.IsPointerish(f.Type.Kind()) {
-			assert.Falsef(t, seenScalar,
-				"field %s (%s, pointer-ish) is declared after a scalar field; "+
-					"pointer fields should precede scalars to shrink GC ptrdata",
-				f.Name, f.Type)
-		} else {
-			seenScalar = true
-		}
-	}
-}
-
 func TestAutoLink_PointerFieldsBeforeScalars(t *testing.T) {
 	// Index 0 is the embedded BaseInline; only AutoLink's own
 	// declared fields are checked here.
-	assertOwnFieldsPointersBeforeScalars(t, reflect.TypeOf(AutoLink{}), 1)
+	fieldorder.AssertPointersBeforeScalars(t, reflect.TypeOf(AutoLink{}), 1)
 }

pkg/goldmark/internal/fieldorder/fieldorder.go

@@ -7,7 +7,10 @@
 // copy of the same reflection logic.
 package fieldorder
 
-import "reflect"
+import (
+	"reflect"
+	"testing"
+)
 
 // IsPointerish reports whether a field's kind carries at least one
 // pointer word that the GC must scan (a pointer, interface, slice,
@@ -20,3 +23,25 @@ func IsPointerish(k reflect.Kind) bool {
 	}
 	return false
 }
+
+// AssertPointersBeforeScalars checks that, among typ's fields
+// starting at index skip (use 1 to skip an embedded base struct), no
+// scalar (non-pointerish) field is followed by a pointerish one. A
+// pointerish field declared after a scalar field extends the struct's
+// GC ptrdata past that scalar for no reason.
+func AssertPointersBeforeScalars(t testing.TB, typ reflect.Type, skip int) {
+	t.Helper()
+	seenScalar := false
+	for i := skip; i < typ.NumField(); i++ {
+		f := typ.Field(i)
+		if IsPointerish(f.Type.Kind()) {
+			if seenScalar {
+				t.Errorf("field %s (%s, pointer-ish) is declared after a scalar field; "+
+					"pointer fields should precede scalars to shrink GC ptrdata",
+					f.Name, f.Type)
+			}
+		} else {
+			seenScalar = true
+		}
+	}
+}

pkg/goldmark/parser/structlayout_test.go

@@ -13,41 +13,19 @@ import (
 	"testing"
 
 	"github.com/jeduden/mdsmith/pkg/goldmark/internal/fieldorder"
-	"github.com/stretchr/testify/assert"
 )
 
-// assertOwnFieldsPointersBeforeScalars checks that, among typ's
-// fields starting at index skip (use 1 to skip an embedded base
-// struct), no scalar (non-pointerish) field is followed by a
-// pointerish one. A pointerish field declared after a scalar field
-// extends the struct's GC ptrdata past that scalar for no reason.
-func assertOwnFieldsPointersBeforeScalars(t *testing.T, typ reflect.Type, skip int) {
-	t.Helper()
-	seenScalar := false
-	for i := skip; i < typ.NumField(); i++ {
-		f := typ.Field(i)
-		if fieldorder.IsPointerish(f.Type.Kind()) {
-			assert.Falsef(t, seenScalar,
-				"field %s (%s, pointer-ish) is declared after a scalar field; "+
-					"pointer fields should precede scalars to shrink GC ptrdata",
-				f.Name, f.Type)
-		} else {
-			seenScalar = true
-		}
-	}
-}
-
 func TestDelimiter_PointerFieldsBeforeScalars(t *testing.T) {
 	// Index 0 is the embedded ast.BaseInline; only Delimiter's own
 	// declared fields are checked here.
-	assertOwnFieldsPointersBeforeScalars(t, reflect.TypeOf(Delimiter{}), 1)
+	fieldorder.AssertPointersBeforeScalars(t, reflect.TypeOf(Delimiter{}), 1)
 }
 
 func TestLinkLabelState_PointerFieldsBeforeScalars(t *testing.T) {
-	assertOwnFieldsPointersBeforeScalars(t, reflect.TypeOf(linkLabelState{}), 1)
+	fieldorder.AssertPointersBeforeScalars(t, reflect.TypeOf(linkLabelState{}), 1)
 }
 
 func TestFenceData_PointerFieldsBeforeScalars(t *testing.T) {
 	// fenceData has no embedded base struct, so every field is checked.
-	assertOwnFieldsPointersBeforeScalars(t, reflect.TypeOf(fenceData{}), 0)
+	fieldorder.AssertPointersBeforeScalars(t, reflect.TypeOf(fenceData{}), 0)
 }