fix corner case in hoist_vars (#4900)

fixes #4898

lib/compress.js

@@ -8438,12 +8438,20 @@ merge(Compressor.prototype, {
             if (value) {
                 if (value instanceof AST_Sequence) value = value.clone();
                 var name = make_node(AST_SymbolRef, defn.name, defn.name);
-                name.fixed = value;
-                a.push(make_node(AST_Assign, defn, {
+                var assign = make_node(AST_Assign, defn, {
                     operator: "=",
                     left: name,
                     right: value,
-                }));
+                });
+                a.push(assign);
+                name.fixed = function() {
+                    return assign.right;
+                };
+                name.fixed.assigns = [ assign ];
+                def.references.forEach(function(ref) {
+                    var assigns = ref.fixed && ref.fixed.assigns;
+                    if (assigns && assigns[0] === defn) assigns[0] = assign;
+                });
                 def.references.push(name);
             }
             def.eliminated++;

test/compress/hoist_vars.js

@@ -232,9 +232,8 @@ issue_4736: {
     expect: {
         (function() {
             (function() {
-                var b = 1 << 30;
                 0,
-                console.log(b);
+                console.log(1073741824);
             })();
         })();
     }
@@ -373,3 +372,27 @@ issue_4893_2: {
     }
     expect_stdout: "PASS"
 }
+
+issue_4898: {
+    options = {
+        collapse_vars: true,
+        evaluate: true,
+        hoist_vars: true,
+        loops: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        do {
+            var b = [ console.log("PASS") ];
+            var c = b;
+        } while (c.p = 0);
+    }
+    expect: {
+        var b;
+        b = [ console.log("PASS") ];
+        b.p = 0;
+    }
+    expect_stdout: "PASS"
+}