fix corner case in hoist_vars (#5864)

fixes #5863

lib/compress.js

@@ -8484,7 +8484,8 @@ Compressor.prototype.compress = function(node) {
                         && self.find_variable(sym.name) === sym.definition();
                 })) return node;
                 node.definitions.forEach(function(defn) {
-                    vars.set(defn.name.name, defn);
+                    var name = defn.name.name;
+                    if (!vars.has(name)) vars.set(name, defn);
                 });
                 var seq = node.to_assignments();
                 if (p instanceof AST_ForEnumeration && p.init === node) {
@@ -8511,13 +8512,14 @@ Compressor.prototype.compress = function(node) {
                     return !ref.in_arg;
                 })) vars.del(argname.name);
             });
-            vars.each(function(defn, name) {
+            vars.each(function(defn) {
+                var name = defn.name;
                 defn = defn.clone();
-                defn.name = defn.name.clone();
+                defn.name = name.clone();
                 defn.value = null;
                 defns.push(defn);
-                vars.set(name, defn);
-                defn.name.definition().orig.unshift(defn.name);
+                var orig = name.definition().orig;
+                orig.splice(orig.indexOf(name), 0, defn.name);
             });
             if (defns.length > 0) hoisted.push(make_node(AST_Var, self, { definitions: defns }));
         }
@@ -10348,8 +10350,8 @@ Compressor.prototype.compress = function(node) {
                     }
                 });
                 def.references.push(name);
+                def.assignments++;
             }
-            def.assignments++;
             def.eliminated++;
             def.single_use = false;
             return a;

test/compress/default-values.js

@@ -3107,3 +3107,31 @@ issue_5774: {
     expect_stdout: "PASS"
     node_version: ">=6"
 }
+
+issue_5863: {
+    options = {
+        collapse_vars: true,
+        hoist_vars: true,
+    }
+    input: {
+        console.log(typeof function f(a = function() {
+            f = 42;
+            return f;
+        }()) {
+            var f;
+            var f;
+            return a;
+        }());
+    }
+    expect: {
+        console.log(typeof function f(a = function() {
+            f = 42;
+            return f;
+        }()) {
+            var f;
+            return a;
+        }());
+    }
+    expect_stdout: "function"
+    node_version: ">=6"
+}