Use removal helpers in more places

src/compiler/checker.ts

@@ -5336,7 +5336,7 @@ namespace ts {
             while (i > 0) {
                 i--;
                 if (isSubtypeOfAny(types[i], types)) {
-                    types.splice(i, 1);
+                    removeItemAt(types, i);
                 }
             }
         }

src/compiler/core.ts

@@ -1394,15 +1394,25 @@ namespace ts {
         }
     }
 
+    /** Remove an item from an array, moving everything to its right one space left. */
+    export function removeItemAt<T>(array: T[], index: number): void {
+        // This seems to be faster than either `array.splice(i, 1)` or `array.copyWithin(i, i+ 1)`.
+        for (let i = index; i < array.length - 1; i++) {
+            array[i] = array[i + 1];
+        }
+        array.pop();
+    }
+
+    /** Remove the *first* occurrence of `item` from the array. */
     export function removeItem<T>(item: T, array: T[]): void {
+        removeFirstItemWhere(array, element => element === item);
+    }
+
+    /** Remove the *first* element satisfying `predicate`. */
+    export function removeFirstItemWhere<T>(array: T[], predicate: (element: T) => boolean): void {
         for (let i = 0; i < array.length; i++) {
-            if (array[i] === item) {
-                // Move everything over to the left.
-                // This seems to be faster than either `array.splice(i, 1)` or `array.copyWithin(i, i+ 1)`.
-                for (; i < array.length - 1; i++) {
-                    array[i] = array[i + 1];
-                }
-                array.pop();
+            if (predicate(array[i])) {
+                removeItemAt(array, i);
                 break;
             }
         }

src/compiler/tsc.ts

@@ -490,10 +490,7 @@ namespace ts {
             sourceFile.fileWatcher.close();
             sourceFile.fileWatcher = undefined;
             if (removed) {
-                const index = rootFileNames.indexOf(sourceFile.fileName);
-                if (index >= 0) {
-                    rootFileNames.splice(index, 1);
-                }
+                removeItem(sourceFile.fileName, rootFileNames);
             }
             startTimerForRecompilation();
         }

src/harness/harness.ts

@@ -1558,7 +1558,7 @@ namespace Harness {
                     tsConfig.options.configFilePath = data.name;
 
                     // delete entry from the list
-                    testUnitData.splice(i, 1);
+                    ts.removeItemAt(testUnitData, i);
 
                     break;
                 }

src/harness/unittests/tsserverProjectSystem.ts

@@ -214,12 +214,7 @@ namespace ts {
                 referenceCount: 0,
                 directoryName,
                 close: () => {
-                    for (let i = 0; i < callbacks.length; i++) {
-                        if (callbacks[i].cb === callback) {
-                            callbacks.splice(i, 1);
-                            break;
-                        }
-                    }
+                    removeFirstItemWhere(callbacks, cb => cb.cb === callback);
                     if (!callbacks.length) {
                         delete this.watchedDirectories[path];
                     }
@@ -253,8 +248,7 @@ namespace ts {
             callbacks.push(callback);
             return {
                 close: () => {
-                    const i = callbacks.indexOf(callback);
-                    callbacks.splice(i, 1);
+                    removeItem(callback, callbacks);
                     if (!callbacks.length) {
                         delete this.watchedFiles[path];
                     }
@@ -269,7 +263,7 @@ namespace ts {
         };
         readonly clearTimeout = (timeoutId: any): void => {
             if (typeof timeoutId === "number") {
-                this.callbackQueue.splice(timeoutId, 1);
+                removeItemAt(this.callbackQueue, timeoutId);
             }
         };
 
@@ -594,7 +588,7 @@ namespace ts {
                 content: `{
                     "compilerOptions": {
                         "target": "es6"
-                    }, 
+                    },
                     "files": [ "main.ts" ]
                 }`
             };
@@ -621,7 +615,7 @@ namespace ts {
                 content: `{
                     "compilerOptions": {
                         "target": "es6"
-                    }, 
+                    },
                     "files": [ "main.ts" ]
                 }`
             };