Learning TypeScript 2.x - Second Edition

Symbols

The TypeScript textbook by Basarat Ali Syed describes symbols as follows:

"Symbols connect declaration nodes in the AST to other declarations contributing to the same entity. Symbols are the basic building block of the Semantic system."

The symbol class is defined in the TypeScript source code as follows:

function Symbol(this: Symbol, flags: SymbolFlags, name: __String) { 
    this.flags = flags; 
    this.escapedName = name; 
    this.declarations = undefined; 
    this.valueDeclaration = undefined; 
    this.id = undefined; 
    this.mergeId = undefined; 
    this.parent = undefined; }

A symbol contains a reference to the declarations of a type and some flags that help us to identify some of its characteristics.