fix corner case in `arguments` (#3421)

fixes #3420

2 files changed, 220 insertions, 0 deletions

diff --git a/test/compress/arguments.js b/test/compress/arguments.js
index eaff8119..119eaf2c 100644
--- a/test/compress/arguments.js
+++ b/test/compress/arguments.js
@@ -622,3 +622,157 @@ issue_3282_2_passes: {
     }
     expect_stdout: true
 }
+
+issue_3420_1: {
+    options = {
+        arguments: true,
+        keep_fargs: "strict",
+    }
+    input: {
+        console.log(function() {
+            return function() {
+                return arguments[0];
+            };
+        }().length);
+    }
+    expect: {
+        console.log(function() {
+            return function() {
+                return arguments[0];
+            };
+        }().length);
+    }
+    expect_stdout: "0"
+}
+
+issue_3420_2: {
+    options = {
+        arguments: true,
+        keep_fargs: "strict",
+    }
+    input: {
+        var foo = function() {
+            delete arguments[0];
+        };
+        foo();
+    }
+    expect: {
+        var foo = function() {
+            delete arguments[0];
+        };
+        foo();
+    }
+    expect_stdout: true
+}
+
+issue_3420_3: {
+    options = {
+        arguments: true,
+        keep_fargs: "strict",
+    }
+    input: {
+        "use strict";
+        var foo = function() {
+            delete arguments[0];
+        };
+        foo();
+    }
+    expect: {
+        "use strict";
+        var foo = function() {
+            delete arguments[0];
+        };
+        foo();
+    }
+    expect_stdout: true
+}
+
+issue_3420_4: {
+    options = {
+        arguments: true,
+        keep_fargs: "strict",
+    }
+    input: {
+        !function() {
+            console.log(arguments[0]);
+            delete arguments[0];
+            console.log(arguments[0]);
+        }(42);
+    }
+    expect: {
+        !function(argument_0) {
+            console.log(argument_0);
+            delete arguments[0];
+            console.log(arguments[0]);
+        }(42);
+    }
+    expect_stdout: [
+        "42",
+        "undefined",
+    ]
+}
+
+issue_3420_5: {
+    options = {
+        arguments: true,
+        keep_fargs: "strict",
+    }
+    input: {
+        "use strict";
+        !function() {
+            console.log(arguments[0]);
+            delete arguments[0];
+            console.log(arguments[0]);
+        }(42);
+    }
+    expect: {
+        "use strict";
+        !function(argument_0) {
+            console.log(argument_0);
+            delete arguments[0];
+            console.log(arguments[0]);
+        }(42);
+    }
+    expect_stdout: [
+        "42",
+        "undefined",
+    ]
+}
+
+issue_3420_6: {
+    options = {
+        arguments: true,
+        keep_fargs: "strict",
+    }
+    input: {
+        console.log(function() {
+            return delete arguments[0];
+        }());
+    }
+    expect: {
+        console.log(function() {
+            return delete arguments[0];
+        }());
+    }
+    expect_stdout: "true"
+}
+
+issue_3420_7: {
+    options = {
+        arguments: true,
+        keep_fargs: "strict",
+    }
+    input: {
+        "use strict";
+        console.log(function() {
+            return delete arguments[0];
+        }());
+    }
+    expect: {
+        "use strict";
+        console.log(function() {
+            return delete arguments[0];
+        }());
+    }
+    expect_stdout: "true"
+}
diff --git a/test/compress/keep_fargs.js b/test/compress/keep_fargs.js
index b23e96f0..558b10bb 100644
--- a/test/compress/keep_fargs.js
+++ b/test/compress/keep_fargs.js
@@ -1051,3 +1051,69 @@ function_name_mangle_ie8: {
     expect_exact: "(function(){console.log(typeof function o(){})})();"
     expect_stdout: "function"
 }
+
+issue_3420_1: {
+    options = {
+        keep_fargs: "strict",
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            return function(a, b, c, d) {
+                return a + b;
+            };
+        }().length);
+    }
+    expect: {
+        console.log(function() {
+            return function(a, b, c, d) {
+                return a + b;
+            };
+        }().length);
+    }
+    expect_stdout: "4"
+}
+
+issue_3420_2: {
+    options = {
+        inline: true,
+        keep_fargs: "strict",
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            return function(a, b, c, d) {
+                return a + b;
+            };
+        }().length);
+    }
+    expect: {
+        console.log(function(a, b, c, d) {
+            return a + b;
+        }.length);
+    }
+    expect_stdout: "4"
+}
+
+issue_3420_3: {
+    options = {
+        inline: true,
+        keep_fargs: "strict",
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            function f(a, b, c, d) {
+                return a + b;
+            }
+            return f;
+        }().length);
+    }
+    expect: {
+        console.log(function(a, b, c, d) {
+            return a + b;
+        }.length);
+    }
+    expect_stdout: "4"
+}