fix corner cases in ie8 (#3485)

fixes #3484

lib/compress.js

@@ -4167,6 +4167,15 @@ merge(Compressor.prototype, {
         }
     });
 
+    function safe_to_drop(fn, compressor) {
+        if (!fn.name || !compressor.option("ie8")) return true;
+        var def = fn.name.definition();
+        if (compressor.exposed(def)) return false;
+        return all(def.references, function(sym) {
+            return !(sym instanceof AST_SymbolRef);
+        });
+    }
+
     // drop_side_effect_free()
     // remove side-effect-free parts which only affects return value
     (function(def) {
@@ -4284,7 +4293,7 @@ merge(Compressor.prototype, {
             return expr.drop_side_effect_free(compressor, first_in_statement);
         });
         def(AST_Function, function(compressor) {
-            return this.name && compressor.option("ie8") ? this : null;
+            return safe_to_drop(this, compressor) ? null : this;
         });
         def(AST_Object, function(compressor, first_in_statement) {
             var values = trim(this.properties, compressor, first_in_statement);
@@ -5170,7 +5179,9 @@ merge(Compressor.prototype, {
                 fn._squeezed = true;
                 return make_sequence(self, flatten_fn()).optimize(compressor);
             }
-            if (compressor.option("side_effects") && all(fn.body, is_empty)) {
+            if (compressor.option("side_effects")
+                && all(fn.body, is_empty)
+                && (fn !== exp || safe_to_drop(fn, compressor))) {
                 var args = self.args.concat(make_node(AST_Undefined, self));
                 return make_sequence(self, args).optimize(compressor);
             }

lib/scope.js

@@ -202,7 +202,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
         if (node instanceof AST_SymbolLambda) {
             var def = node.thedef;
             redefine(node, node.scope.parent_scope.resolve());
-            node.thedef.init = def.init;
+            if (def.init) node.thedef.init = def.init;
             return true;
         }
     }));

test/compress/ie8.js

@@ -1683,3 +1683,161 @@ issue_3482_2_ie8: {
     }
     expect_stdout: "NaN NaN NaN"
 }
+
+issue_3484_1: {
+    options = {
+        ie8: false,
+        side_effects: true,
+        toplevel: false,
+    }
+    input: {
+        (function f() {})();
+        console.log(typeof f);
+    }
+    expect: {
+        console.log(typeof f);
+    }
+    expect_stdout: "undefined"
+}
+
+issue_3484_1_ie8: {
+    options = {
+        ie8: true,
+        side_effects: true,
+        toplevel: false,
+    }
+    input: {
+        (function f() {})();
+        // IE8: function
+        console.log(typeof f);
+    }
+    expect: {
+        (function f() {})();
+        console.log(typeof f);
+    }
+    expect_stdout: "undefined"
+}
+
+issue_3484_1_toplevel: {
+    options = {
+        ie8: false,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        (function f() {})();
+        console.log(typeof f);
+    }
+    expect: {
+        console.log(typeof f);
+    }
+    expect_stdout: "undefined"
+}
+
+issue_3484_1_ie8_toplevel: {
+    options = {
+        ie8: true,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        (function f() {})();
+        // IE8: function
+        console.log(typeof f);
+    }
+    expect: {
+        (function f() {})();
+        console.log(typeof f);
+    }
+    expect_stdout: "undefined"
+}
+
+issue_3484_2: {
+    options = {
+        evaluate: true,
+        ie8: false,
+        reduce_vars: true,
+        toplevel: false,
+    }
+    input: {
+        (function Infinity() {
+            var Infinity;
+        })();
+        console.log(typeof (1 / 0), typeof Infinity);
+    }
+    expect: {
+        (function Infinity() {
+            var Infinity;
+        })();
+        console.log("number", "number");
+    }
+    expect_stdout: "number number"
+}
+
+issue_3484_2_ie8: {
+    options = {
+        evaluate: true,
+        ie8: true,
+        reduce_vars: true,
+        toplevel: false,
+    }
+    input: {
+        (function Infinity() {
+            var Infinity;
+        })();
+        // IE8: number function
+        console.log(typeof (1 / 0), typeof Infinity);
+    }
+    expect: {
+        (function Infinity() {
+            var Infinity;
+        })();
+        console.log("number", typeof Infinity);
+    }
+    expect_stdout: "number number"
+}
+
+issue_3484_2_toplevel: {
+    options = {
+        evaluate: true,
+        ie8: false,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        (function Infinity() {
+            var Infinity;
+        })();
+        console.log(typeof (1 / 0), typeof Infinity);
+    }
+    expect: {
+        (function Infinity() {
+            var Infinity;
+        })();
+        console.log("number", "number");
+    }
+    expect_stdout: "number number"
+}
+
+issue_3484_2_ie8_toplevel: {
+    options = {
+        evaluate: true,
+        ie8: true,
+        reduce_vars: true,
+        toplevel: true,
+    }
+    input: {
+        (function Infinity() {
+            var Infinity;
+        })();
+        // IE8: number function
+        console.log(typeof (1 / 0), typeof Infinity);
+    }
+    expect: {
+        (function Infinity() {
+            var Infinity;
+        })();
+        console.log("number", typeof Infinity);
+    }
+    expect_stdout: "number number"
+}