Fix js-optimizer crash on empty array destructuring element

Followup to emscripten-core#20835. Fixes: emscripten-core#20818
sbc100 · Dec 5, 2023 · 95b30a8 · 95b30a8
1 parent fb0d986
commit 95b30a8
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Showing 3 changed files with 5 additions and 3 deletions.
diff --git a/test/optimizer/JSDCE-objectPattern-output.js b/test/optimizer/JSDCE-objectPattern-output.js
@@ -5,7 +5,7 @@ let z = 50;
 globalThis.f = function(r) {
  let {a: a, b: b} = r;
  let {z: c} = r;
- let [i, {foo: p, bar: q}] = r;
+ let [, i, {foo: p, bar: q}] = r;
  return g(a, b, c, d, z);
 };
 

diff --git a/test/optimizer/JSDCE-objectPattern.js b/test/optimizer/JSDCE-objectPattern.js
@@ -13,7 +13,7 @@ let z = 50;
 globalThis.f = function(r) {
   let { a, b } = r;
   let { z: c } = r;
-  let [i, {foo : p, bar : q}] = r;
+  let [/*empty*/, i, {foo : p, bar : q}] = r;
   return g(a, b, c, d, z);
 };
 

diff --git a/tools/acorn-optimizer.js b/tools/acorn-optimizer.js
@@ -429,18 +429,20 @@ function runJSDCE(ast, aggressive) {
         function traverse(id) {
           if (id.type === 'ObjectPattern') {
             for (const prop of id.properties) {
+              assertAt(prop.value, id);
               traverse(prop.value);
             }
           } else if (id.type === 'ArrayPattern') {
             for (const elem of id.elements) {
-              traverse(elem);
+              if (elem) traverse(elem);
             }
           } else {
             assertAt(id.type === 'Identifier', id, `expected Indentifier but found ${id.type}`);
             const name = id.name;
             ensureData(scopes[scopes.length - 1], name).def = 1;
           }
         }
+        assertAt(node, node);
         traverse(node.id);
         if (node.init) c(node.init);
       },