Microsoft/TypeScript
1
0
Fork 0
mirror of https://github.com/microsoft/TypeScript.git synced 2025-11-18 17:21:48 +00:00
Code Issues Packages Projects Releases Wiki Activity

Additional documentation

Browse Source
This commit is contained in:
Ron Buckton
2017-10-05 11:34:42 -07:00
parent 906a79df76
commit 180ca23384
1 changed files with 47 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/compiler/checker.ts
+47 -16
View File
@@ -5573,6 +5573,25 @@ namespace ts {
* Performs late-binding of a dynamic member. This performs the same function for
* late-bound members that `declareSymbol` in binder.ts performs for early-bound
* members.
*
* If a symbol is a dynamic name from a computed property, we perform an additional "late"
* binding phase to attempt to resolve the name for the symbol from the type of the computed
* property's expression. If the type of the expression is a string-literal, numeric-literal,
* or unique symbol type, we can use that type as the name of the symbol.
*
* For example, given:
*
* const x = Symbol();
*
* interface I {
* [x]: number;
* }
*
* The binder gives the property `[x]: number` a special symbol with the name "__computed".
* In the late-binding phase we can type-check the expression `x` and see that it has a
* unique symbol type which we can then use as the name of the member. This allows users
* to define custom symbols that can be used in the members of an object type.
*
* @param parent The containing symbol for the member.
* @param earlySymbols The early-bound symbols of the parent.
* @param lateSymbols The late-bound symbols of the parent.
@@ -5590,26 +5609,26 @@ namespace ts {
const memberName = getLateBoundNameFromType(type);
// Get or add a late-bound symbol for the member. This allows us to merge late-bound accessor declarations.
let symbol = lateSymbols.get(memberName);
if (!symbol) lateSymbols.set(memberName, symbol = createSymbol(SymbolFlags.Late, memberName));
let lateSymbol = lateSymbols.get(memberName);
if (!lateSymbol) lateSymbols.set(memberName, lateSymbol = createSymbol(SymbolFlags.Late, memberName));
// Report an error if a late-bound member has the same name as an early-bound member,
// or if we have another early-bound symbol declaration with the same name and
// conflicting flags.
const earlySymbol = earlySymbols && earlySymbols.get(memberName);
if (symbol.flags & getExcludedSymbolFlags(decl.symbol.flags) || earlySymbol) {
if (lateSymbol.flags & getExcludedSymbolFlags(decl.symbol.flags) || earlySymbol) {
// If we have an existing early-bound member, combine its declarations so that we can
// report an error at each declaration.
const declarations = earlySymbol ? concatenate(earlySymbol.declarations, symbol.declarations) : symbol.declarations;
const declarations = earlySymbol ? concatenate(earlySymbol.declarations, lateSymbol.declarations) : lateSymbol.declarations;
const name = declarationNameToString(decl.name);
forEach(declarations, declaration => error(getNameOfDeclaration(declaration) || declaration, Diagnostics.Duplicate_declaration_0, name));
error(decl.name || decl, Diagnostics.Duplicate_declaration_0, name);
symbol = createSymbol(SymbolFlags.Late, memberName);
lateSymbol = createSymbol(SymbolFlags.Late, memberName);
}
addDeclarationToLateBoundSymbol(symbol, decl, decl.symbol.flags);
symbol.parent = parent;
return links.resolvedSymbol = symbol;
addDeclarationToLateBoundSymbol(lateSymbol, decl, decl.symbol.flags);
lateSymbol.parent = parent;
return links.resolvedSymbol = lateSymbol;
}
}
return links.resolvedSymbol;
@@ -5617,16 +5636,22 @@ namespace ts {
/**
* Gets a SymbolTable containing both the early- and late-bound members of a symbol.
*
* For a description of late-binding, see `lateBindMember`.
*/
function getMembersOfSymbol(symbol: Symbol) {
if (symbol.flags & SymbolFlags.LateBindableContainer) {
const links = getSymbolLinks(symbol);
if (!links.resolvedMembers) {
const earlyMembers = symbol.members;
// Get (or create) the SymbolTable from the parent used to store late-
// bound symbols. We get a shared table so that we can correctly merge
// late-bound symbols across accessor pairs.
const lateMembers = getLateBoundMembersOfSymbol(symbol);
const earlyMembers = symbol.members;
// In the event we recursively resolve the members of the symbol, we
// should only see the early-bound members of the symbol here.
// set the initial value of resolvedMembers to the early-bound members
// of the symbol.
links.resolvedMembers = earlyMembers || emptySymbols;
// fill in any as-yet-unresolved late-bound members.
@@ -5635,11 +5660,12 @@ namespace ts {
if (members) {
for (const member of members) {
if (!hasModifier(member, ModifierFlags.Static) && hasLateBindableName(member)) {
lateBindMember(decl.symbol, earlyMembers, lateMembers, member);
lateBindMember(symbol, earlyMembers, lateMembers, member);
}
}
}
}
links.resolvedMembers = combineSymbolTables(earlyMembers, lateMembers) || emptySymbols;
}
return links.resolvedMembers;
@@ -5648,11 +5674,9 @@ namespace ts {
}
/**
* Gets the late-bound symbol for a symbol (if it has one). The symbol is
* resolved dynamically but allows accessors to share the same symbol.
* If a symbol is the dynamic name of the member of an object type, get its late-bound member.
*
* We do not aggressively resolve the entire late-bound symbol table here as
* that requires a type-check on every computed property name.
* For a description of late-binding, see `lateBindMember`.
*/
function getLateBoundSymbol(symbol: Symbol) {
if (symbol && (symbol.flags & SymbolFlags.ClassMember) && symbol.escapedName === InternalSymbolName.Computed) {
@@ -5661,8 +5685,15 @@ namespace ts {
if (parent && (parent.flags & (isStaticMember ? SymbolFlags.Class : SymbolFlags.LateBindableContainer))) {
const links = getSymbolLinks(symbol);
if (!links.lateSymbol) {
const earlySymbols = isStaticMember ? parent.exports : parent.members;
// Get (or create) the SymbolTable from the parent used to store late-
// bound symbols. We get a shared table so that we can correctly merge
// late-bound symbols across accessor pairs.
//
// We do not eagerly resolve all of the members of the parent here as
// that results in an eager type-check of the expression of every member
// with a computed property name.
const lateSymbols = isStaticMember ? getLateBoundExportsOfSymbol(parent) : getLateBoundMembersOfSymbol(parent);
const earlySymbols = isStaticMember ? parent.exports : parent.members;
// In the event we attempt to get the late-bound symbol for a symbol recursively,
// fall back to the early-bound symbol.