fix corner cases with instanceof (#5509)

- enhance `evaluate`

lib/compress.js

@@ -2452,7 +2452,7 @@ Compressor.prototype.compress = function(node) {
 
             function is_last_node(node, parent) {
                 if (node instanceof AST_Await) return true;
-                if (node.TYPE == "Binary") return node.operator == "in" && !is_object(node.right);
+                if (node.TYPE == "Binary") return !can_drop_op(node.operator, node.right);
                 if (node instanceof AST_Call) {
                     var def, fn = node.expression;
                     if (fn instanceof AST_SymbolRef) {
@@ -5551,7 +5551,7 @@ Compressor.prototype.compress = function(node) {
         def(AST_Binary, function(compressor) {
             return this.left.has_side_effects(compressor)
                 || this.right.has_side_effects(compressor)
-                || this.operator == "in" && !is_object(this.right);
+                || !can_drop_op(this.operator, this.right);
         });
         def(AST_Block, function(compressor) {
             return any(this.body, compressor);
@@ -5705,7 +5705,7 @@ Compressor.prototype.compress = function(node) {
         def(AST_Binary, function(compressor) {
             return this.left.may_throw(compressor)
                 || this.right.may_throw(compressor)
-                || this.operator == "in" && !is_object(this.right);
+                || !can_drop_op(this.operator, this.right);
         });
         def(AST_Block, function(compressor) {
             return any(this.body, compressor);
@@ -5822,7 +5822,7 @@ Compressor.prototype.compress = function(node) {
         def(AST_Binary, function(scope) {
             return this.left.is_constant_expression(scope)
                 && this.right.is_constant_expression(scope)
-                && (this.operator != "in" || is_object(this.right));
+                && can_drop_op(this.operator, this.right);
         });
         def(AST_Class, function(scope) {
             var base = this.extends;
@@ -8533,7 +8533,7 @@ Compressor.prototype.compress = function(node) {
             var left = this.left;
             var right = this.right;
             var op = this.operator;
-            if (op == "in" && !is_object(right)) {
+            if (!can_drop_op(op, right)) {
                 var lhs = left.drop_side_effect_free(compressor, first_in_statement);
                 if (lhs === left) return this;
                 var node = this.clone();
@@ -11202,6 +11202,18 @@ Compressor.prototype.compress = function(node) {
             || node instanceof AST_Object;
     }
 
+    function can_drop_op(op, rhs) {
+        switch (op) {
+          case "in":
+            return is_object(rhs);
+          case "instanceof":
+            if (rhs instanceof AST_SymbolRef) rhs = rhs.fixed_value();
+            return is_lambda(rhs);
+          default:
+            return true;
+        }
+    }
+
     function is_primitive(compressor, node) {
         if (node.is_constant()) return true;
         if (node instanceof AST_Assign) return node.operator != "=" || is_primitive(compressor, node.right);
@@ -11708,6 +11720,12 @@ Compressor.prototype.compress = function(node) {
                     }
                 }
                 break;
+              case "instanceof":
+                if (is_lambda(self.right)) return make_sequence(self, [
+                    self,
+                    make_node(AST_False, self),
+                ]).optimize(compressor);
+                break;
             }
             if (!(parent instanceof AST_UnaryPrefix && parent.operator == "delete")) {
                 if (self.left instanceof AST_Number && !self.right.is_constant()) switch (self.operator) {

lib/output.js

@@ -260,6 +260,15 @@ function OutputStream(options) {
 
     var require_semicolon = makePredicate("( [ + * / - , .");
 
+    function require_space(prev, ch, str) {
+        return is_identifier_char(prev) && (is_identifier_char(ch) || ch == "\\")
+            || (ch == "/" && ch == prev)
+            || ((ch == "+" || ch == "-") && ch == last)
+            || last == "--" && ch == ">"
+            || last == "!" && str == "--"
+            || prev == "/" && (str == "in" || str == "instanceof");
+    }
+
     var print = options.beautify
         || options.comments
         || options.max_line_len
@@ -312,12 +321,7 @@ function OutputStream(options) {
         }
 
         if (might_need_space) {
-            if (is_identifier_char(prev) && (is_identifier_char(ch) || ch == "\\")
+            if (require_space(prev, ch, str)) {
-                || (ch == "/" && ch == prev)
-                || ((ch == "+" || ch == "-") && ch == last)
-                || str == "--" && last == "!"
-                || str == "in" && prev == "/"
-                || last == "--" && ch == ">") {
                 output += " ";
                 current_col++;
             }
@@ -355,14 +359,7 @@ function OutputStream(options) {
             }
         }
         if (might_need_space) {
-            if (is_identifier_char(prev) && (is_identifier_char(ch) || ch == "\\")
+            if (require_space(prev, ch, str)) output += " ";
-                || (ch == "/" && ch == prev)
-                || ((ch == "+" || ch == "-") && ch == last)
-                || str == "--" && last == "!"
-                || str == "in" && prev == "/"
-                || last == "--" && ch == ">") {
-                output += " ";
-            }
             if (prev != "<" || str != "!") might_need_space = false;
         }
         output += str;
@@ -1819,9 +1816,6 @@ function OutputStream(options) {
               case "\u2029": return "\\u2029";
             }
         }));
-        var p = output.parent();
-        if (p instanceof AST_Binary && /^in/.test(p.operator) && p.left === this)
-            output.print(" ");
     });
 
     function force_statement(stat, output) {

test/compress/awaits.js

@@ -1293,6 +1293,21 @@ functions_inner_var: {
     node_version: ">=8"
 }
 
+instanceof_lambda: {
+    options = {
+        evaluate: true,
+        side_effects: true,
+    }
+    input: {
+        console.log(42 instanceof async function() {});
+    }
+    expect: {
+        console.log(false);
+    }
+    expect_stdout: "false"
+    node_version: ">=8"
+}
+
 issue_4335_1: {
     options = {
         inline: true,

test/compress/classes.js

@@ -1266,6 +1266,23 @@ keep_fnames: {
     node_version: ">=4"
 }
 
+instanceof_lambda: {
+    options = {
+        evaluate: true,
+        side_effects: true,
+    }
+    input: {
+        "use strict";
+        console.log(42 instanceof class {});
+    }
+    expect: {
+        "use strict";
+        console.log(false);
+    }
+    expect_stdout: "false"
+    node_version: ">=4"
+}
+
 issue_805_1: {
     options = {
         inline: true,

test/compress/evaluate.js

@@ -907,6 +907,20 @@ chained_side_effects: {
     ]
 }
 
+instanceof_lambda: {
+    options = {
+        evaluate: true,
+        side_effects: true,
+    }
+    input: {
+        console.log(42 instanceof function() {});
+    }
+    expect: {
+        console.log(false);
+    }
+    expect_stdout: "false"
+}
+
 issue_1649: {
     options = {
         evaluate: true,

test/compress/pure_funcs.js

@@ -147,7 +147,7 @@ relational: {
         "bar" >= "bar";
     }
     expect: {
-        bar();
+        0 instanceof bar();
         bar();
         bar(), bar();
         bar();

test/compress/regexp.js

@@ -50,6 +50,22 @@ regexp_properties: {
     expect_stdout: "abc true false 0 false"
 }
 
+instanceof_1: {
+    input: {
+        console.log(/foo/ instanceof RegExp);
+    }
+    expect_exact: "console.log(/foo/ instanceof RegExp);"
+    expect_stdout: "true"
+}
+
+instanceof_2: {
+    input: {
+        console.log(42 + /foo/ instanceof Object);
+    }
+    expect_exact: "console.log(42+/foo/ instanceof Object);"
+    expect_stdout: "false"
+}
+
 issue_3434_1: {
     options = {
         evaluate: true,

test/compress/side_effects.js

@@ -645,3 +645,56 @@ issue_4751: {
     }
     expect_stdout: "PASS"
 }
+
+drop_instanceof: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        42 instanceof function() {};
+        console.log("PASS");
+    }
+    expect: {
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+}
+
+drop_instanceof_reference: {
+    options = {
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+    }
+    input: {
+        function f() {}
+        42 instanceof f;
+        console.log("PASS");
+    }
+    expect: {
+        function f() {}
+        console.log("PASS");
+    }
+    expect_stdout: "PASS"
+}
+
+retain_instanceof: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        try {
+            42 instanceof "foo";
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect: {
+        try {
+            0 instanceof "foo";
+        } catch (e) {
+            console.log("PASS");
+        }
+    }
+    expect_stdout: "PASS"
+}

test/compress/yields.js

@@ -934,6 +934,21 @@ drop_unused_call: {
     node_version: ">=4"
 }
 
+instanceof_lambda: {
+    options = {
+        evaluate: true,
+        side_effects: true,
+    }
+    input: {
+        console.log(42 instanceof function*() {});
+    }
+    expect: {
+        console.log(false);
+    }
+    expect_stdout: "false"
+    node_version: ">=4"
+}
+
 issue_4454_1: {
     rename = false
     options = {

test/ufuzz/index.js

@@ -253,7 +253,7 @@ BINARY_OPS = BINARY_OPS.concat(BINARY_OPS);
 if (SUPPORT.exponentiation) BINARY_OPS.push("**");
 BINARY_OPS = BINARY_OPS.concat(BINARY_OPS);
 BINARY_OPS = BINARY_OPS.concat(BINARY_OPS);
-BINARY_OPS.push(" in ");
+BINARY_OPS.push(" in ", " instanceof ");
 
 var ASSIGNMENTS = [ "=" ];
 ASSIGNMENTS = ASSIGNMENTS.concat(ASSIGNMENTS);
@@ -2009,7 +2009,7 @@ function createBinaryOp(noComma, canThrow) {
     var op;
     do {
         op = BINARY_OPS[rng(BINARY_OPS.length)];
-    } while (noComma && op == "," || !canThrow && op == " in ");
+    } while (noComma && op == "," || !canThrow && /^ in/.test(op));
     return op;
 }