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Unified Diff: lib/src/codegen/js_codegen.dart

Issue 1243503007: fixes #221, initial sync*, async, async* implementation (Closed) Base URL: git@github.com:dart-lang/dev_compiler.git@master
Patch Set: Created 5 years, 5 months ago
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Index: lib/src/codegen/js_codegen.dart
diff --git a/lib/src/codegen/js_codegen.dart b/lib/src/codegen/js_codegen.dart
index a20b3799c0412b9e9cc952b87c0753909900112e..0e4c39b0f2b455d34ef1fd5be92c9032eb752ab6 100644
--- a/lib/src/codegen/js_codegen.dart
+++ b/lib/src/codegen/js_codegen.dart
@@ -67,6 +67,9 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
/// The variable for the current catch clause
SimpleIdentifier _catchParameter;
+ /// In an async* function, this represents the stream controller parameter.
+ JS.TemporaryId _asyncStarController;
+
/// Imported libraries, and the temporaries used to refer to them.
final _imports = new Map<LibraryElement, JS.TemporaryId>();
final _exports = new Set<String>();
@@ -1165,7 +1168,7 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
if (params == null) params = <JS.Parameter>[];
return new JS.Method(
- _elementMemberName(node.element), _emitJsFunction(params, node.body),
+ _elementMemberName(node.element), _emitFunctionBody(params, node.body),
isGetter: node.isGetter,
isSetter: node.isSetter,
isStatic: node.isStatic);
@@ -1252,19 +1255,22 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
var parent = node.parent;
var inStmt = parent.parent is FunctionDeclarationStatement;
if (parent is FunctionDeclaration) {
- return _emitJsFunction(params, node.body);
+ return _emitFunctionBody(params, node.body);
} else {
String code;
- AstNode body;
- var nodeBody = node.body;
- if (nodeBody is ExpressionFunctionBody) {
+ JS.Node jsBody;
+ var body = node.body;
+ if (body.isGenerator || body.isAsynchronous) {
+ code = '(#) => #';
+ jsBody = _emitGeneratorFunctionBody(params, body);
+ } else if (body is ExpressionFunctionBody) {
code = '(#) => #';
- body = nodeBody.expression;
+ jsBody = _visit(body.expression);
} else {
code = '(#) => { #; }';
- body = nodeBody;
+ jsBody = _visit(body);
}
- var clos = js.call(code, [params, _visit(body)]);
+ var clos = js.call(code, [params, jsBody]);
if (!inStmt) {
var type = getStaticType(node);
return _emitFunctionTagged(clos, type,
@@ -1274,10 +1280,69 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
}
}
- JS.Fun _emitJsFunction(List<JS.Parameter> params, FunctionBody body) {
- // TODO(jmesserly): async/async*
- var syncStar = body.isSynchronous && body.star != null;
- return new JS.Fun(params, _visit(body), isGenerator: syncStar);
+ JS.Fun _emitFunctionBody(List<JS.Parameter> params, FunctionBody body) {
+ // sync*, async, async*
+ if (body.isAsynchronous || body.isGenerator) {
+ return new JS.Fun(params, js.statement(
+ '{ return #; }', [_emitGeneratorFunctionBody(params, body)]));
+ }
+ // normal function (sync)
+ return new JS.Fun(params, _visit(body));
+ }
+
+ JS.Expression _emitGeneratorFunctionBody(
+ List<JS.Parameter> params, FunctionBody body) {
+ var kind = body.isSynchronous ? 'sync' : 'async';
+ if (body.isGenerator) kind += 'Star';
+
+ // Transforms `sync*` `async` and `async*` function bodies
+ // using ES6 generators.
+ //
+ // `sync*` wraps a generator in a Dart Iterable<T>:
+ //
+ // function name(<args>) {
+ // return dart.syncStar(function*(<args>) {
+ // <body>
+ // }, T, <args>).bind(this);
+ // }
+ //
+ // We need to include <args> in case any are mutated, so each `.iterator`
+ // gets the same initial values.
+ //
+ // TODO(jmesserly): we could omit the args for the common case where args
+ // are not mutated inside the generator.
+ //
+ // In the future, we might be able to simplify this, see:
+ // https://github.com/dart-lang/dev_compiler/issues/247.
+ //
+ // `async` works the same, but uses the `dart.async` helper.
+ //
+ // In the body of a `sync*` and `async`, `yield`/`await` are both generated
+ // simply as `yield`.
+ //
+ // `async*` uses the `dart.asyncStar` helper, and also has an extra `stream`
+ // argument to the generator, which is used for passing values to the
+ // _AsyncStarStreamController implementation type.
+ // `yield` is specially generated inside `async*`, see visitYieldStatement.
+ // `await` is generated as `yield`.
+ // runtime/_generators.js has an example of what the code is generated as.
+ var savedController = _asyncStarController;
+ List jsParams;
+ if (kind == 'asyncStar') {
+ _asyncStarController = new JS.TemporaryId('stream');
+ jsParams = [_asyncStarController]..addAll(params);
+ } else {
+ _asyncStarController = null;
+ jsParams = params;
+ }
+ JS.Expression gen = new JS.Fun(jsParams, _visit(body), isGenerator: true);
+ if (JS.This.foundIn(gen)) {
+ gen = js.call('#.bind(this)', gen);
+ }
+ _asyncStarController = savedController;
+
+ var T = _emitTypeName(rules.getExpectedReturnType(body));
+ return js.call('dart.#(#)', [kind, [gen, T]..addAll(params)]);
}
@override
@@ -1708,7 +1773,33 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
@override
JS.Statement visitYieldStatement(YieldStatement node) {
JS.Expression jsExpr = _visit(node.expression);
- return jsExpr.toYieldStatement(star: node.star != null);
+ var star = node.star != null;
+ if (_asyncStarController != null) {
+ // async* yields are generated differently from sync* yields. `yield e`
+ // becomes:
+ //
+ // if (stream.add(e)) return;
+ // yield;
+ //
+ // `yield* e` becomes:
+ //
+ // if (stream.addStream(e)) return;
+ // yield;
+ var helperName = star ? 'addStream' : 'add';
+ return js.statement('{ if(#.#(#)) return; #; }', [
+ _asyncStarController,
+ helperName,
+ jsExpr,
+ new JS.Yield(null)
+ ]);
+ }
+ // A normal yield in a sync*
+ return jsExpr.toYieldStatement(star: star);
+ }
+
+ @override
+ JS.Expression visitAwaitExpression(AwaitExpression node) {
+ return new JS.Yield(_visit(node.expression));
}
@override
@@ -2414,7 +2505,11 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
}
@override
- JS.ForOf visitForEachStatement(ForEachStatement node) {
+ JS.Statement visitForEachStatement(ForEachStatement node) {
+ if (node.awaitKeyword != null) {
+ return _emitAwaitFor(node);
+ }
+
var init = _visit(node.identifier);
if (init == null) {
init = js.call('let #', node.loopVariable.identifier.name);
@@ -2422,6 +2517,58 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
return new JS.ForOf(init, _visit(node.iterable), _visit(node.body));
}
+ JS.Statement _emitAwaitFor(ForEachStatement node) {
+ // Emits `await for (var value in stream) ...`, which desugars as:
+ //
+ // var iter = new StreamIterator<T>(stream);
+ // try {
+ // while (await iter.moveNext()) {
+ // var value = iter.current;
+ // ...
+ // }
+ // } finally {
+ // await iter.cancel();
+ // }
+ //
+ // Like the Dart VM, we call cancel() always, as it's safe to call if the
+ // stream has already been cancelled.
+ //
+ // TODO(jmesserly): we may want a helper if these become common. For now the
+ // full desugaring seems okay.
+ var context = compiler.context;
+ var dart_async = context
+ .computeLibraryElement(context.sourceFactory.forUri('dart:async'));
+ var T = node.loopVariable.element.type;
+ var StreamIterator_T =
+ dart_async.getType('StreamIterator').type.substitute4([T]);
+
+ var createStreamIter = _emitInstanceCreationExpression(
+ StreamIterator_T.element.unnamedConstructor, StreamIterator_T, null,
+ AstBuilder.argumentList([node.iterable]), false);
+ var iter = _visit(_createTemporary('it', StreamIterator_T));
+
+ var init = _visit(node.identifier);
+ if (init == null) {
+ init = js.call(
+ 'let # = #.current', [node.loopVariable.identifier.name, iter]);
+ } else {
+ init = js.call('# = #.current', [init, iter]);
+ }
+ return js.statement('{'
+ ' let # = #;'
+ ' try {'
+ ' while (#) { #; #; }'
+ ' } finally { #; }'
+ '}', [
+ iter,
+ createStreamIter,
+ new JS.Yield(js.call('#.moveNext()', iter)),
+ init,
+ _visit(node.body),
+ new JS.Yield(js.call('#.cancel()', iter))
+ ]);
+ }
+
@override
visitBreakStatement(BreakStatement node) {
var label = node.label;
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