Revision: 4745
Author: erights
Date: Mon Jan 2 04:40:07 2012
Log: Fixed the expansion of completion values.
http://code.google.com/p/google-caja/source/detail?r=4745
Modified:
/trunk/experimental/src/com/google/caja/ses/expandProgramToExpr.js
=======================================
--- /trunk/experimental/src/com/google/caja/ses/expandProgramToExpr.js Tue
Dec 27 23:22:53 2011
+++ /trunk/experimental/src/com/google/caja/ses/expandProgramToExpr.js Mon
Jan 2 04:40:07 2012
@@ -23,7 +23,7 @@
* <p>Serves as pseudo-code until we can run it. This section explains
* what more is needed to turn this into running code.
*
- * We express our translations using JavaScript <a href=
+ * <p>We express our translations using JavaScript <a href=
* "http://wiki.ecmascript.org/doku.php?id=harmony:quasis";
* >quasiliterals</a> and a hypothetical JavaScript quasi-parser named
* "js". We additionally assume that the expression syntax {a, b} is
@@ -40,26 +40,26 @@
* "http://wiki.ecmascript.org/doku.php?id=strawman:object_initialiser_shorthand#discussion";
* >object initializer discussion</a> section.
*
- * Together, this means that (quasiParser`stuff${{varName}}stuff`) can
- * create an object that can be used as a pattern, placing the values
- * extracted from the specimen into varName, which must have already
- * been declared. As a further elaboration, we assume predicate
- * pattern functions that wrap such a literal
+ * <p>Together, this means that (quasiParser`stuff${{varName}}stuff`)
+ * can create an object that can be used as a pattern, placing the
+ * values extracted from the specimen into varName, which must have
+ * already been declared. As a further elaboration, we assume
+ * predicate pattern functions that wrap such a literal
* (quasiParser`stuff${isThing({varName})}stuff`) and report whether
* the proposed assignment meets it criteria. If not, that match
* fails.
*
- * Separately from the rules below, we also prohibit identifiers
+ * <p>Separately from the rules below, we also prohibit identifiers
* ending in ___ (triple underbar) in the input, so that we may use
* them in the output without fear of capture.
*
- * The JavaScript quasiParser accepts one additional element besides
+ * <p>The JavaScript quasiParser accepts one additional element besides
* JavaScript syntax and $ holes. In addition, when an "*", "+", or
* "?" appears immediately to the right of a $ hole with no
* intervening space, then it is taken as a quantifier on the binding
* of the $ hole to consecutive AST elements.
*
- * Besides the "js" quasi-parser, the following code depends on the
+ * <p>Besides the "js" quasi-parser, the following code depends on the
* following helper functions. Depending on the concrete AST
* representation chosen, perhaps some of these should instead be uses
* of AST methods. Refactor as needed.<ul>
@@ -76,7 +76,7 @@
* <li>makeAstLike - like arg, with alternate children
* </ul>
*
- * The expanded code assumes bindings for<ul>
+ * <p>The expanded code assumes bindings for<ul>
* <li>declareGlobal___
* <li>defineGlobal___
* <li>cleanErr___
@@ -88,7 +88,7 @@
* license to translate by other means. This condition aborts the
* overall translation.
*
- * When translating a Source-SES script program, as might appear
+ * <p>When translating a Source-SES script program, as might appear
* between script tags, declareGlobal___ and defineGlobal___ should
* mutate the virtual global, enabling inter-module linkage. When
* translating a Source-SES eval program, as might be passed to an
@@ -129,28 +129,12 @@
* Translate a Source-SES Program production AST, as might appear
* in Source-SES script or eval code, into a Target-SES Expression
* production AST suitable for giving to cajaVM.compileExpr.
- *
- * This expander fixes the "Completion Value" anomaly of
- * Target-SES, using the "completion value reform" semantics
- * proposed for ES6.
*/
expandProgramToExpr = function expandProgramToExpr(ast) {
- if (!isProgram.test(ast)) { return null; }
- var prog, expr;
-
- if (js`${isStatementOrDecl({prog})}*
- ${isExpr({expr})}`.test(ast)) {
-
+ if (isProgram.test(ast)) {
return js`(function(global___) {
- ${expandAll(prog)}*
- return ${expand(expr)};
- }).call(this, this)`
- }
- if (js`${isStatementOrDecl({prog})}*`.test(ast)) {
-
- return js`(function(global___) {
- ${expandAll(prog)}*
- }).call(this, this)`
+ ${returnCompletion(ast)}
+ }).call(this, this)`;
}
return null;
}
@@ -179,8 +163,8 @@
if (firstTokenName) {
expander = byStartToken(firstTokenName);
if (expander) {
- result = expander(ast);
- if (result) { return result; }
+ result = expander(ast);
+ if (result) { return result; }
}
}
for (var i = 0, len = others.length; i++) {
@@ -194,7 +178,7 @@
}
/**
- * This expander fixed the "Top Level Declarations" anomaly of
+ * This expander fixes the "Top Level Declarations" anomaly of
* Target-SES.
*/
function expandTopDecl(ast) {
@@ -285,4 +269,54 @@
return null;
}
byStartToken.set('try', expandTryCatch);
+
+ /**
+ * Expand a Source-SES AST fragement occuring is a top
+ * level-context that could return a <a href=
+ * "http://wiki.ecmascript.org/doku.php?id=harmony:completion_reform";
+ * >completion value</a> and return a corresponding Target-SES
+ * fragment to appear at a similar location in a function body,
+ * where the expression that would compute the completion value is
+ * preceded by "return", so that this value is instead returned as
+ * the value of the enclosing function.
+ *
+ * <p>This expander fixes the "Completion Value" anomaly of
+ * Target-SES, using the <a href=
+ * "http://wiki.ecmascript.org/doku.php?id=harmony:completion_reform";
+ * >completion value reform</a> semantics proposed for ES6.
+ */
+ function returnCompletion(ast) {
+ var allButLast, last, expr, then, els, body;
+
+ if (js``.test(ast)) { return js``; }
+
+ if (js`${isStatementOrDecl({allButLast})}*
+ ${isStatementOrDecl({last})}`.test(ast)) {
+
+ return js`${expandAll(allButLast)}*
+ ${returnCompletion(last)}`
+ if (js``.test(ast)) { return js``; }
+
+
+ if (js`${isExpr(expr);}.test(ast) {
+ return js`return ${expand(expr)};`;
+ }
+ if (js`if ($expr) $then $els`.test(ast)) {
+
+ return js`if (${expand(expr)})
+ ${returnCompletion(then)}
+ ${returnCompletion(els)}`;
+ }
+ if (js`while ($expr) $body`.test(ast)) {
+
+ return js`while (${expand($expr))} ${returnCompletion(body)}`;
+ }
+
+ // TODO(erights): If any other statements can produce
+ // completion values according to the completion value reform
+ // semantics, place them here.
+
+ return expand(ast);
+ }
+
})();
