stop create_symbol symbol generator from creating symbols which confl…

…ict in inner scopes. Closes #851
terser · Oct 18, 2020 · 3357170 · 3357170
1 parent 8a42649
commit 3357170
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Showing 3 changed files with 60 additions and 2 deletions.
diff --git a/lib/compress/index.js b/lib/compress/index.js
@@ -4270,9 +4270,14 @@ AST_Scope.DEFMETHOD("hoist_properties", function(compressor) {
                 const defs = new Map();
                 const assignments = [];
                 value.properties.forEach(({ key, value }) => {
+                    const scope = find_scope(hoister);
                     const symbol = self.create_symbol(sym.CTOR, {
                         source: sym,
-                        scope: find_scope(hoister),
+                        scope,
+                        conflict_scopes: new Set([
+                            scope,
+                            ...sym.definition().references.map(ref => ref.scope)
+                        ]),
                         tentative_name: sym.name + "_" + key
                     });
 

diff --git a/lib/scope.js b/lib/scope.js
@@ -493,6 +493,13 @@ AST_Scope.DEFMETHOD("conflicting_def", function (name) {
     );
 });
 
+AST_Scope.DEFMETHOD("conflicting_def_shallow", function (name) {
+    return (
+        this.enclosed.find(def => def.name === name)
+        || this.variables.has(name)
+    );
+});
+
 AST_Scope.DEFMETHOD("add_child_scope", function (scope) {
     // `scope` is going to be moved into `this` right now.
     // Update the required scopes' information
@@ -526,23 +533,42 @@ AST_Scope.DEFMETHOD("add_child_scope", function (scope) {
     }
 });
 
+function find_scopes_visible_from(scopes) {
+    const found_scopes = new Set();
+
+    for (const scope of new Set(scopes)) {
+        (function bubble_up(scope) {
+            if (scope == null || found_scopes.has(scope)) return;
+
+            found_scopes.add(scope);
+
+            bubble_up(scope.parent_scope);
+        })(scope);
+    }
+
+    return [...found_scopes];
+}
+
 // Creates a symbol during compression
 AST_Scope.DEFMETHOD("create_symbol", function(SymClass, {
     source,
     tentative_name,
     scope,
+    conflict_scopes = [scope],
     init = null
 } = {}) {
     let symbol_name;
 
+    conflict_scopes = find_scopes_visible_from(conflict_scopes);
+
     if (tentative_name) {
         // Implement hygiene (no new names are conflicting with existing names)
         tentative_name =
             symbol_name =
             tentative_name.replace(/(?:^[^a-z_$]|[^a-z0-9_$])/ig, "_");
 
         let i = 0;
-        while (this.conflicting_def(symbol_name)) {
+        while (conflict_scopes.find(s => s.conflicting_def_shallow(symbol_name))) {
             symbol_name = tentative_name + "$" + i++;
         }
     }

diff --git a/test/compress/hoist_props.js b/test/compress/hoist_props.js
@@ -1098,3 +1098,30 @@ does_not_hoist_objects_with_computed_props: {
     }
     expect_stdout: "PASS"
 }
+
+issue_851_hoist_to_conflicting_name: {
+    options = {
+        hoist_props: true,
+        reduce_vars: true,
+        toplevel: true
+    }
+    input: {
+        const BBB = { CCC: "PASS" }
+
+        if (id(true)) {
+            const BBB_CCC = BBB.CCC
+            console.log(BBB_CCC)
+        }
+    }
+
+    expect: {
+        const BBB_CCC$0 = "PASS";
+
+        if (id(true)) {
+            const BBB_CCC = BBB_CCC$0;
+            console.log(BBB_CCC);
+        }
+    }
+
+    expect_stdout: "PASS"
+}