Prefer instanceof Dict rather than calling isDict() with one argument

Unless you actually need to check that something is both a `Dict` and also of the *correct* type, using `instanceof Dict` directly should be a tiny bit more efficient since it avoids one function call and an unnecessary `undefined` check.

This patch uses ESLint to enforce this, since we obviously still want to keep the `isDict` helper function for where it makes sense.

src/core/annotation.js

@@ -39,7 +39,7 @@ import {
   createDefaultAppearance,
   parseDefaultAppearance,
 } from "./default_appearance.js";
-import { Dict, isDict, isName, Name, Ref, RefSet } from "./primitives.js";
+import { Dict, isName, Name, Ref, RefSet } from "./primitives.js";
 import { BaseStream } from "./base_stream.js";
 import { bidi } from "./bidi.js";
 import { Catalog } from "./catalog.js";
@@ -95,7 +95,7 @@ class AnnotationFactory {
     pageIndex = -1
   ) {
     const dict = xref.fetchIfRef(ref);
-    if (!isDict(dict)) {
+    if (!(dict instanceof Dict)) {
       return undefined;
     }
 
@@ -209,7 +209,7 @@ class AnnotationFactory {
   static async _getPageIndex(xref, ref, pdfManager) {
     try {
       const annotDict = await xref.fetchIfRefAsync(ref);
-      if (!isDict(annotDict)) {
+      if (!(annotDict instanceof Dict)) {
         return -1;
       }
       const pageRef = annotDict.getRaw("P");
@@ -636,7 +636,7 @@ class Annotation {
     }
 
     this.borderStyle = new AnnotationBorderStyle();
-    if (!isDict(borderStyle)) {
+    if (!(borderStyle instanceof Dict)) {
       return;
     }
     if (borderStyle.has("BS")) {
@@ -681,7 +681,7 @@ class Annotation {
     this.appearance = null;
 
     const appearanceStates = dict.get("AP");
-    if (!isDict(appearanceStates)) {
+    if (!(appearanceStates instanceof Dict)) {
       return;
     }
 
@@ -691,7 +691,7 @@ class Annotation {
       this.appearance = normalAppearanceState;
       return;
     }
-    if (!isDict(normalAppearanceState)) {
+    if (!(normalAppearanceState instanceof Dict)) {
       return;
     }
 
@@ -1418,7 +1418,7 @@ class WidgetAnnotation extends Annotation {
     const { xref } = evaluator;
 
     const dict = xref.fetchIfRef(this.ref);
-    if (!isDict(dict)) {
+    if (!(dict instanceof Dict)) {
       return null;
     }
 
@@ -2085,7 +2085,7 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
     }
 
     const dict = evaluator.xref.fetchIfRef(this.ref);
-    if (!isDict(dict)) {
+    if (!(dict instanceof Dict)) {
       return null;
     }
 
@@ -2131,7 +2131,7 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
     }
 
     const dict = evaluator.xref.fetchIfRef(this.ref);
-    if (!isDict(dict)) {
+    if (!(dict instanceof Dict)) {
       return null;
     }
 
@@ -2158,7 +2158,7 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
         parentBuffer = [`${this.parent.num} ${this.parent.gen} obj\n`];
         writeDict(parent, parentBuffer, parentTransform);
         parentBuffer.push("\nendobj\n");
-      } else if (isDict(this.parent)) {
+      } else if (this.parent instanceof Dict) {
         this.parent.set("V", name);
       }
     }
@@ -2250,12 +2250,12 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
 
   _processCheckBox(params) {
     const customAppearance = params.dict.get("AP");
-    if (!isDict(customAppearance)) {
+    if (!(customAppearance instanceof Dict)) {
       return;
     }
 
     const normalAppearance = customAppearance.get("N");
-    if (!isDict(normalAppearance)) {
+    if (!(normalAppearance instanceof Dict)) {
       return;
     }
 
@@ -2318,7 +2318,7 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
     // The parent field's `V` entry holds a `Name` object with the appearance
     // state of whichever child field is currently in the "on" state.
     const fieldParent = params.dict.get("Parent");
-    if (isDict(fieldParent)) {
+    if (fieldParent instanceof Dict) {
       this.parent = params.dict.getRaw("Parent");
       const fieldParentValue = fieldParent.get("V");
       if (isName(fieldParentValue)) {
@@ -2328,11 +2328,11 @@ class ButtonWidgetAnnotation extends WidgetAnnotation {
 
     // The button's value corresponds to its appearance state.
     const appearanceStates = params.dict.get("AP");
-    if (!isDict(appearanceStates)) {
+    if (!(appearanceStates instanceof Dict)) {
       return;
     }
     const normalAppearance = appearanceStates.get("N");
-    if (!isDict(normalAppearance)) {
+    if (!(normalAppearance instanceof Dict)) {
       return;
     }
     for (const key of normalAppearance.getKeys()) {