Use more explicit operations in core helpers (and other nits)

src/compiler/checker.ts

@@ -17,10 +17,10 @@ import {
     appendIfUnique,
     ArrayBindingPattern,
     arrayFrom,
+    arrayIsEqualTo,
     arrayIsHomogeneous,
     ArrayLiteralExpression,
     arrayOf,
-    arraysEqual,
     arrayToMultiMap,
     ArrayTypeNode,
     ArrowFunction,
@@ -25860,7 +25860,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     function inferTypesFromTemplateLiteralType(source: Type, target: TemplateLiteralType): Type[] | undefined {
         return source.flags & TypeFlags.StringLiteral ? inferFromLiteralPartsToTemplateLiteral([(source as StringLiteralType).value], emptyArray, target) :
             source.flags & TypeFlags.TemplateLiteral ?
-            arraysEqual((source as TemplateLiteralType).texts, target.texts) ? map((source as TemplateLiteralType).types, (s, i) => {
+            arrayIsEqualTo((source as TemplateLiteralType).texts, target.texts) ? map((source as TemplateLiteralType).types, (s, i) => {
                 return isTypeAssignableTo(getBaseConstraintOrType(s), getBaseConstraintOrType(target.types[i])) ? s : getStringLikeTypeForType(s);
             }) :
                 inferFromLiteralPartsToTemplateLiteral((source as TemplateLiteralType).texts, (source as TemplateLiteralType).types, target) :
@@ -28625,7 +28625,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 return getEvolvingArrayType(getUnionType(map(types, getElementTypeOfEvolvingArrayType)));
             }
             const result = recombineUnknownType(getUnionType(sameMap(types, finalizeEvolvingArrayType), subtypeReduction));
-            if (result !== declaredType && result.flags & declaredType.flags & TypeFlags.Union && arraysEqual((result as UnionType).types, (declaredType as UnionType).types)) {
+            if (result !== declaredType && result.flags & declaredType.flags & TypeFlags.Union && arrayIsEqualTo((result as UnionType).types, (declaredType as UnionType).types)) {
                 return declaredType;
             }
             return result;

src/compiler/commandLineParser.ts

@@ -2580,9 +2580,7 @@ export function convertToTSConfig(configParseResult: ParsedCommandLine, configFi
 
 /** @internal */
 export function optionMapToObject(optionMap: Map<string, CompilerOptionsValue>): object {
-    return {
-        ...arrayFrom(optionMap.entries()).reduce((prev, cur) => ({ ...prev, [cur[0]]: cur[1] }), {}),
-    };
+    return Object.fromEntries(optionMap);
 }
 
 function filterSameAsDefaultInclude(specs: readonly string[] | undefined) {

src/compiler/debug.ts

@@ -61,6 +61,7 @@ import {
     LiteralType,
     map,
     MatchingKeys,
+    maxBy,
     ModifierFlags,
     Node,
     NodeArray,
@@ -1126,7 +1127,7 @@ m2: ${(this.mapper2 as unknown as DebugTypeMapper).__debugToString().split("\n")
 
         function renderGraph() {
             const columnCount = columnWidths.length;
-            const laneCount = nodes.reduce((x, n) => Math.max(x, n.lane), 0) + 1;
+            const laneCount = maxBy(nodes, 0, n => n.lane) + 1;
             const lanes: string[] = fill(Array(laneCount), "");
             const grid: (FlowGraphNode | undefined)[][] = columnWidths.map(() => Array(laneCount));
             const connectors: Connection[][] = columnWidths.map(() => fill(Array(laneCount), 0));

src/compiler/scanner.ts

@@ -1,6 +1,6 @@
 import {
     append,
-    arraysEqual,
+    arrayIsEqualTo,
     binarySearch,
     CharacterCodes,
     CommentDirective,
@@ -475,7 +475,7 @@ export function computePositionOfLineAndCharacter(lineStarts: readonly number[],
             line = line < 0 ? 0 : line >= lineStarts.length ? lineStarts.length - 1 : line;
         }
         else {
-            Debug.fail(`Bad line number. Line: ${line}, lineStarts.length: ${lineStarts.length} , line map is correct? ${debugText !== undefined ? arraysEqual(lineStarts, computeLineStarts(debugText)) : "unknown"}`);
+            Debug.fail(`Bad line number. Line: ${line}, lineStarts.length: ${lineStarts.length} , line map is correct? ${debugText !== undefined ? arrayIsEqualTo(lineStarts, computeLineStarts(debugText)) : "unknown"}`);
         }
     }
 

src/compiler/watch.ts

@@ -74,6 +74,7 @@ import {
     isReferenceFileLocation,
     isString,
     last,
+    maxBy,
     maybeBind,
     memoize,
     ModuleKind,
@@ -305,7 +306,7 @@ function createTabularErrorsDisplay(filesInError: (ReportFileInError | undefined
 
     const numberLength = (num: number) => Math.log(num) * Math.LOG10E + 1;
     const fileToErrorCount = distinctFiles.map(file => ([file, countWhere(filesInError, fileInError => fileInError!.fileName === file!.fileName)] as const));
-    const maxErrors = fileToErrorCount.reduce((acc, value) => Math.max(acc, value[1] || 0), 0);
+    const maxErrors = maxBy(fileToErrorCount, 0, value => value[1]);
 
     const headerRow = Diagnostics.Errors_Files.message;
     const leftColumnHeadingLength = headerRow.split(" ")[0].length;

src/harness/fourslashImpl.ts

@@ -2642,17 +2642,12 @@ export class TestState {
         if (info === undefined) return "No completion info.";
         const { entries } = info;
 
-        function pad(s: string, length: number) {
-            return s + new Array(length - s.length + 1).join(" ");
-        }
-        function max<T>(arr: T[], selector: (x: T) => number): number {
-            return arr.reduce((prev, x) => Math.max(prev, selector(x)), 0);
-        }
-        const longestNameLength = max(entries, m => m.name.length);
-        const longestKindLength = max(entries, m => m.kind.length);
+        const longestNameLength = ts.maxBy(entries, 0, m => m.name.length);
+        const longestKindLength = ts.maxBy(entries, 0, m => m.kind.length);
         entries.sort((m, n) => m.sortText > n.sortText ? 1 : m.sortText < n.sortText ? -1 : m.name > n.name ? 1 : m.name < n.name ? -1 : 0);
-        const membersString = entries.map(m => `${pad(m.name, longestNameLength)} ${pad(m.kind, longestKindLength)} ${m.kindModifiers} ${m.isRecommended ? "recommended " : ""}${m.source === undefined ? "" : m.source}`).join("\n");
-        Harness.IO.log(membersString);
+
+        const formattedEntries = entries.map(m => `${m.name.padEnd(longestNameLength)} ${m.kind.padEnd(longestKindLength)} ${m.kindModifiers} ${m.isRecommended ? "recommended " : ""}${m.source ?? ""}`);
+        Harness.IO.log(formattedEntries.join("\n"));
     }
 
     public printContext() {

src/server/editorServices.ts

@@ -76,7 +76,6 @@ import {
     LanguageServiceMode,
     length,
     map,
-    mapDefinedEntries,
     mapDefinedIterator,
     missingFileModifiedTime,
     MultiMap,
@@ -4273,14 +4272,15 @@ export class ProjectService {
 
     /** @internal */
     loadAncestorProjectTree(forProjects?: ReadonlyCollection<string>) {
-        forProjects = forProjects || mapDefinedEntries(
-            this.configuredProjects,
-            (key, project) => !project.isInitialLoadPending() ? [key, true] : undefined,
+        forProjects ??= new Set(
+            mapDefinedIterator(this.configuredProjects.entries(), ([key, project]) => !project.isInitialLoadPending() ? key : undefined),
         );
 
         const seenProjects = new Set<NormalizedPath>();
-        // Work on array copy as we could add more projects as part of callback
-        for (const project of arrayFrom(this.configuredProjects.values())) {
+        // We must copy the current configured projects into a separate array,
+        // as we could end up creating and adding more projects indirectly.
+        const currentConfiguredProjects = arrayFrom(this.configuredProjects.values());
+        for (const project of currentConfiguredProjects) {
             // If this project has potential project reference for any of the project we are loading ancestor tree for
             // load this project first
             if (forEachPotentialProjectReference(project, potentialRefPath => forProjects.has(potentialRefPath))) {

src/services/jsDoc.ts

@@ -1,5 +1,5 @@
 import {
-    arraysEqual,
+    arrayIsEqualTo,
     ArrowFunction,
     AssignmentDeclarationKind,
     BinaryExpression,
@@ -222,7 +222,7 @@ export function getJsDocCommentsFromDeclarations(declarations: readonly Declarat
 }
 
 function isIdenticalListOfDisplayParts(parts1: SymbolDisplayPart[], parts2: SymbolDisplayPart[]) {
-    return arraysEqual(parts1, parts2, (p1, p2) => p1.kind === p2.kind && p1.text === p2.text);
+    return arrayIsEqualTo(parts1, parts2, (p1, p2) => p1.kind === p2.kind && p1.text === p2.text);
 }
 
 function getCommentHavingNodes(declaration: Declaration): readonly (JSDoc | JSDocTag)[] {