improve evaluate on typeof (#2550)

- gated through `typeofs`

lib/compress.js

@@ -1828,12 +1828,17 @@ merge(Compressor.prototype, {
             return this;
         });
         def(AST_UnaryPrefix, function(compressor){
+            var e = this.expression;
             // Function would be evaluated to an array and so typeof would
             // incorrectly return 'object'. Hence making is a special case.
-            if (this.operator == "typeof" && this.expression instanceof AST_Function) {
+            if (compressor.option("typeofs")
+                && this.operator == "typeof"
+                && (e instanceof AST_Lambda
+                    || e instanceof AST_SymbolRef
+                        && e.fixed_value() instanceof AST_Lambda)) {
                 return typeof function(){};
             }
-            var e = ev(this.expression, compressor);
+            e = ev(e, compressor);
             if (e === this.expression) return this;
             switch (this.operator) {
               case "!": return !e;
@@ -1894,7 +1899,6 @@ merge(Compressor.prototype, {
             return value === node ? this : value;
         });
         def(AST_SymbolRef, function(compressor){
-            if (!compressor.option("reduce_vars")) return this;
             var fixed = this.fixed_value();
             if (!fixed) return this;
             this._eval = return_this;

test/compress/typeof.js

@@ -1,6 +1,7 @@
 typeof_evaluation: {
     options = {
-        evaluate: true
+        evaluate: true,
+        typeofs: true,
     };
     input: {
         a = typeof 1;
@@ -60,3 +61,80 @@ issue_1668: {
         if (1);
     }
 }
+
+typeof_defun_1: {
+    options = {
+        evaluate: true,
+        inline: true,
+        passes: 2,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        typeofs: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            console.log("YES");
+        }
+        function g() {
+            h = 42;
+            console.log("NOPE");
+        }
+        function h() {
+            console.log("YUP");
+        }
+        g = 42;
+        "function" == typeof f && f();
+        "function" == typeof g && g();
+        "function" == typeof h && h();
+    }
+    expect: {
+        function g() {
+            h = 42;
+            console.log("NOPE");
+        }
+        function h() {
+            console.log("YUP");
+        }
+        g = 42;
+        console.log("YES");
+        "function" == typeof g && g();
+        h();
+    }
+    expect_stdout: [
+        "YES",
+        "YUP",
+    ]
+}
+
+typeof_defun_2: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        typeofs: true,
+    }
+    input: {
+        var f = function() {
+            console.log(x);
+        };
+        var x = 0;
+        x++ < 2 && typeof f == "function" && f();
+        x++ < 2 && typeof f == "function" && f();
+        x++ < 2 && typeof f == "function" && f();
+    }
+    expect: {
+        var f = function() {
+            console.log(x);
+        };
+        var x = 0;
+        x++ < 2 && f();
+        x++ < 2 && f();
+        x++ < 2 && f();
+    }
+    expect_stdout: [
+        "1",
+        "2",
+    ]
+}