Vue.js

The official TypeScript compiler and language service implementation. This is the core codebase that powers TypeScript - a typed superset of JavaScript that compiles to plain JavaScript. It includes the compiler (tsc), the language server (tsserver) for IDE integration, and all the tooling infrastructure for type checking, code transformation, and developer experience features.

Tech Stack

Vue.jsAngularTypeScriptReactPrismatRPCExpress.jsPostgreSQL

Key Features

Type Checker
Code Emission
Language Server (tsserver)
Incremental Compilation
Code Fixes & Refactors
tsconfig.json Parsing
Library Definitions

Coding Conventions

Standards and patterns used in this codebase

Naming Conventions

Use PascalCase for types, interfaces, enums, and namespaces. Use camelCase for functions, variables, and parameters. Prefix internal/private functions with underscore.

interface SymbolTable { ... }
function createBinder(): ... { }
function getNodeId(node: Node): number { }
let _hasError: boolean;

src/compiler/binder.tssrc/compiler/checker.ts

Module Structure

Use namespace declarations for internal module organization. Export public APIs explicitly. Group related functionality into logical namespaces like 'ts' for core compiler APIs.

namespace ts {
    export function createProgram(...): Program { }
    function internalHelper() { }
}

src/compiler/binder.tssrc/compiler/builder.ts

Enum Definitions

Use const enums for performance-critical flags and regular enums for public APIs. Enum members use PascalCase. Bit flags use powers of 2 with explicit numeric values.

const enum ContainerFlags {
    None = 0,
    IsContainer = 1 << 0,
    IsBlockScopedContainer = 1 << 1,
    IsControlFlowContainer = 1 << 2
}

src/compiler/binder.tssrc/compiler/types.ts

Function Organization

Define helper functions inside closures to access shared state without passing parameters. Use factory functions that return objects with methods for complex stateful operations.

function createBinder() {
    let file: SourceFile;
    let container: Node;
    return bindSourceFile;
    function bindSourceFile(f: SourceFile) { ... }
    function bind(node: Node) { ... }
}

src/compiler/binder.tssrc/compiler/checker.ts

Debug Assertions

Use Debug.assert(), Debug.assertEqual(), Debug.assertNode() for runtime invariant checking. Include descriptive messages. Use Debug.type<T>() for type narrowing assertions.

Debug.assert(googleprovider !== undefined);
Debug.assertEqual(googleprovider.kind, SyntaxKind.SourceFile);
Debug.assertNode(node, isExpression);

src/compiler/binder.tssrc/compiler/checker.ts

Switch Statement Pattern

Use exhaustive switch statements with Debug.fail() or Debug.assertNever() in default case to catch unhandled enum values. Group related cases together.

switch (node.kind) {
    case SyntaxKind.Identifier:
        return bindIdentifier(node);
    case SyntaxKind.BinaryExpression:
        return bindBinaryExpression(node);
    default:
        Debug.assertNever(node);

src/compiler/binder.tssrc/compiler/factory/nodeTests.ts

Build System

Use Hereby task runner with async task functions. Define tasks with dependencies using task() function. Use glob patterns for file inputs and explicit outputs for caching.

export const buildSrc = task({
    name: "build-src",
    dependencies: [generateDiagnostics],
    run: async () => {
        await buildProject("src/tsconfig.json");
    }
});

Herebyfile.mjs

ESLint Configuration

Use flat config format with TypeScript ESLint. Disable rules that conflict with TypeScript's type system. Enable strict rules for internal code, relaxed for tests.

rules: {
    "@typescript-eslint/no-unnecessary-qualifier": "error",
    "@typescript-eslint/unified-signatures": "error",
    "no-restricted-syntax": ["error", { selector: "Literal[raw=null]", message: "Use 'undefined' instead of 'null'" }]
}

eslint.config.mjs

Diagnostic Messages

Define diagnostics in JSON with category, code, and message template. Use numbered placeholders {0}, {1} for interpolation. Generate TypeScript constants from JSON definitions.

"Cannot_find_name_0": {
    "category": "Error",
    "code": 2304,
    "message": "Cannot find name '{0}'."
}

scripts/processDiagnosticMessages.mjssrc/compiler/diagnosticInformationMap.generated.ts

Control Flow Analysis

Model control flow as a graph with FlowNode types. Use bit flags for flow node kinds. Track antecedents for branches and loops. Use unreachable flow for dead code.

interface FlowCondition extends FlowNodeBase {
    node: Expression;
    antecedent: FlowNode;
}
const enum FlowFlags {
    Unreachable = 1,
    Start = 2,
    BranchLabel = 4,
    LoopLabel = 8
}

src/compiler/binder.tssrc/compiler/types.ts