SymbolTable is implemented as a simple HashMap. Here is the interface (types.ts
):
interface SymbolTable {[index: string]: Symbol;}
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 membersexports?: SymbolTable; // Module exports
Note: We saw locals
getting initialized (to {}
) by bindChildren
based on ContainerFlags
.
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 declarationslet 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);}