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SymbolTable SymbolTable is implemented as a simple HashMap. Here is the interface (types.ts):

interface SymbolTable {

} SymbolTables are initialized by binding. There are a few SymbolTables used by the compiler:

On Node:

locals?: SymbolTable; // Locals associated with node On Symbol:

members?: SymbolTable; // Class, interface or literal instance members exports?: SymbolTable; // Module exports Note: We saw locals getting initialized (to {}) by bindChildren based on ContainerFlags.

SymbolTable population SymbolTables are populated with Symbols primarily by a call to declareSymbol. This function is presented below in entirety:

/**

• Declares a Symbol for the node and adds it to symbols. Reports errors for conflicting identifier names.

• @param symbolTable - The symbol table which node will be added to.

• @param parent - node's parent declaration.

• @param node - The declaration to be added to the symbol table

• @param includes - The SymbolFlags that node has in addition to its declaration type (eg: export, ambient, etc.)

• @param excludes - The flags which node cannot be declared alongside in a symbol table. Used to report forbidden declarations. */ function declareSymbol(symbolTable: SymbolTable, parent: Symbol, node: Declaration, includes: SymbolFlags, excludes: SymbolFlags): Symbol { Debug.assert(!hasDynamicName(node));

  // The exported symbol for an export default function/class node is always named "default"
  let name = node.flags & NodeFlags.Default && parent ? "default" : getDeclarationName(node);
  
  let symbol: Symbol;
  if (name !== undefined) {
  
      // Check and see if the symbol table already has a symbol with this name.  If not,
      // create a new symbol with this name and add it to the table.  Note that we don't
      // give the new symbol any flags *yet*.  This ensures that it will not conflict
      // with the 'excludes' flags we pass in.
      //
      // If we do get an existing symbol, see if it conflicts with the new symbol we're
      // creating.  For example, a 'var' symbol and a 'class' symbol will conflict within
      // the same symbol table.  If we have a conflict, report the issue on each
      // declaration we have for this symbol, and then create a new symbol for this
      // declaration.
      //
      // If we created a new symbol, either because we didn't have a symbol with this name
      // in the symbol table, or we conflicted with an existing symbol, then just add this
      // node as the sole declaration of the new symbol.
      //
      // Otherwise, we'll be merging into a compatible existing symbol (for example when
      // you have multiple 'vars' with the same name in the same container).  In this case
      // just add this node into the declarations list of the symbol.
      symbol = hasProperty(symbolTable, name)
          ? symbolTable[name]
          : (symbolTable[name] = createSymbol(SymbolFlags.None, name));
  
      if (name && (includes & SymbolFlags.Classifiable)) {
          classifiableNames[name] = name;
      }
  
      if (symbol.flags & excludes) {
          if (node.name) {
              node.name.parent = node;
          }
  
          // Report errors every position with duplicate declaration
          // Report errors on previous encountered declarations
          let message = symbol.flags & SymbolFlags.BlockScopedVariable
              ? Diagnostics.Cannot_redeclare_block_scoped_variable_0
              : Diagnostics.Duplicate_identifier_0;
          forEach(symbol.declarations, declaration => {
              file.bindDiagnostics.push(createDiagnosticForNode(declaration.name || declaration, message, getDisplayName(declaration)));
          });
          file.bindDiagnostics.push(createDiagnosticForNode(node.name || node, message, getDisplayName(node)));
  
          symbol = createSymbol(SymbolFlags.None, name);
      }
  }
  else {
      symbol = createSymbol(SymbolFlags.None, "__missing");
  }
  
  addDeclarationToSymbol(symbol, node, includes);
  symbol.parent = parent;
  
  return symbol;

  } Which SymbolTable is populated is driven by the first argument to this function. e.g. when adding a declaration to a container of kind SyntaxKind.ClassDeclaration or SyntaxKind.ClassExpression the function declareClassMember will get called which has the following code:

function declareClassMember(node: Declaration, symbolFlags: SymbolFlags, symbolExcludes: SymbolFlags) { return node.flags & NodeFlags.Static ? declareSymbol(container.symbol.exports, container.symbol, node, symbolFlags, symbolExcludes) : declareSymbol(container.symbol.members, container.symbol, node, symbolFlags, symbolExcludes); }