Add 'clear' helper (#17209)

Author: Andy

src/compiler/checker.ts

@@ -22266,8 +22266,8 @@ namespace ts {
                 // Grammar checking
                 checkGrammarSourceFile(node);
 
-                potentialThisCollisions.length = 0;
-                potentialNewTargetCollisions.length = 0;
+                clear(potentialThisCollisions);
+                clear(potentialNewTargetCollisions);
 
                 deferredNodes = [];
                 deferredUnusedIdentifierNodes = produceDiagnostics && noUnusedIdentifiers ? [] : undefined;
@@ -22293,12 +22293,12 @@ namespace ts {
 
                 if (potentialThisCollisions.length) {
                     forEach(potentialThisCollisions, checkIfThisIsCapturedInEnclosingScope);
-                    potentialThisCollisions.length = 0;
+                    clear(potentialThisCollisions);
                 }
 
                 if (potentialNewTargetCollisions.length) {
                     forEach(potentialNewTargetCollisions, checkIfNewTargetIsCapturedInEnclosingScope);
-                    potentialNewTargetCollisions.length = 0;
+                    clear(potentialNewTargetCollisions);
                 }
 
                 links.flags |= NodeCheckFlags.TypeChecked;

src/compiler/core.ts

@@ -384,6 +384,10 @@ namespace ts {
         array.length = outIndex;
     }
 
+    export function clear(array: {}[]): void {
+        array.length = 0;
+    }
+
     export function map<T, U>(array: ReadonlyArray<T>, f: (x: T, i: number) => U): U[] {
         let result: U[];
         if (array) {

src/harness/unittests/tsserverProjectSystem.ts

@@ -561,7 +561,7 @@ namespace ts.projectSystem {
         }
 
         clearOutput() {
-            this.output.length = 0;
+            clear(this.output);
         }
 
         readonly readFile = (s: string) => (<File>this.fs.get(this.toPath(s))).content;

src/server/builder.ts

@@ -223,7 +223,7 @@ namespace ts.server {
             for (const reference of this.references) {
                 reference.removeReferencedBy(this);
             }
-            this.references = createSortedArray<ModuleBuilderFileInfo>();
+            clear(this.references);
         }
     }
 

src/server/scriptInfo.ts

@@ -242,7 +242,7 @@ namespace ts.server {
                 // detach is unnecessary since we'll clean the list of containing projects anyways
                 p.removeFile(this, /*detachFromProjects*/ false);
             }
-            this.containingProjects.length = 0;
+            clear(this.containingProjects);
         }
 
         getDefaultProject() {

src/services/shims.ts

@@ -1176,7 +1176,7 @@ namespace ts {
 
         public close(): void {
             // Forget all the registered shims
-            this._shims = [];
+            clear(this._shims);
             this.documentRegistry = undefined;
         }