diff --git a/README.md b/README.md
index 1d64fcb2..8ec101f6 100644
--- a/README.md
+++ b/README.md
@@ -443,6 +443,11 @@ to set `true`; it's effectively a shortcut for `foo=true`).
 - `keep_infinity` -- default `false`. Pass `true` to prevent `Infinity` from
   being compressed into `1/0`, which may cause performance issues on Chrome.
 
+- `side_effects` -- default `false`. Pass `true` to potentially drop functions
+marked as "pure".  (A function is marked as "pure" via the comment annotation
+`/* @__PURE__ */` or `/* #__PURE__ */`)
+
+
 ### The `unsafe` option
 
 It enables some transformations that *might* break code logic in certain
diff --git a/lib/compress.js b/lib/compress.js
index 8454a432..d0f9668c 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -326,10 +326,14 @@ merge(Compressor.prototype, {
                     // So existing transformation rules can work on them.
                     node.argnames.forEach(function(arg, i) {
                         var d = arg.definition();
-                        d.fixed = function() {
-                            return iife.args[i] || make_node(AST_Undefined, iife);
-                        };
-                        mark(d, true);
+                        if (!node.uses_arguments && d.fixed === undefined) {
+                            d.fixed = function() {
+                                return iife.args[i] || make_node(AST_Undefined, iife);
+                            };
+                            mark(d, true);
+                        } else {
+                            d.fixed = false;
+                        }
                     });
                 }
                 if (node instanceof AST_If || node instanceof AST_DWLoop) {
@@ -414,7 +418,9 @@ merge(Compressor.prototype, {
 
         function reset_def(def) {
             def.escaped = false;
-            if (toplevel || !def.global || def.orig[0] instanceof AST_SymbolConst) {
+            if (def.scope.uses_eval) {
+                def.fixed = false;
+            } else if (toplevel || !def.global || def.orig[0] instanceof AST_SymbolConst) {
                 def.fixed = undefined;
             } else {
                 def.fixed = false;
@@ -440,6 +446,14 @@ merge(Compressor.prototype, {
         return fixed();
     });
 
+    function is_reference_const(ref) {
+        if (!(ref instanceof AST_SymbolRef)) return false;
+        var orig = ref.definition().orig;
+        for (var i = orig.length; --i >= 0;) {
+            if (orig[i] instanceof AST_SymbolConst) return true;
+        }
+    }
+
     function find_variable(compressor, name) {
         var scope, i = 0;
         while (scope = compressor.parent(i++)) {
@@ -1909,6 +1923,7 @@ merge(Compressor.prototype, {
                         && node instanceof AST_Assign
                         && node.operator == "="
                         && node.left instanceof AST_SymbolRef
+                        && !is_reference_const(node.left)
                         && scope === self) {
                         node.right.walk(tw);
                         return true;
@@ -3066,7 +3081,8 @@ merge(Compressor.prototype, {
             }
             if (left
                 && !(left instanceof AST_SymbolRef
-                    && left.definition().orig[0] instanceof AST_SymbolLambda)) {
+                    && (left.definition().orig[0] instanceof AST_SymbolLambda
+                        || is_reference_const(left)))) {
                 var parent, field;
                 var cdr = self.cdr;
                 while (true) {
diff --git a/test/compress/collapse_vars.js b/test/compress/collapse_vars.js
index 2264783d..53ae8f4e 100644
--- a/test/compress/collapse_vars.js
+++ b/test/compress/collapse_vars.js
@@ -1592,3 +1592,49 @@ var_side_effects_3: {
     }
     expect_stdout: true
 }
+
+reassign_const_1: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        function f() {
+            const a = 1;
+            a = 2;
+            return a;
+        }
+        console.log(f());
+    }
+    expect: {
+        function f() {
+            const a = 1;
+            a = 2;
+            return a;
+        }
+        console.log(f());
+    }
+    expect_stdout: true
+}
+
+reassign_const_2: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        function f() {
+            const a = 1;
+            ++a;
+            return a;
+        }
+        console.log(f());
+    }
+    expect: {
+        function f() {
+            const a = 1;
+            ++a;
+            return a;
+        }
+        console.log(f());
+    }
+    expect_stdout: true
+}
diff --git a/test/compress/drop-unused.js b/test/compress/drop-unused.js
index 9d37dc7e..7a2f86a9 100644
--- a/test/compress/drop-unused.js
+++ b/test/compress/drop-unused.js
@@ -1064,3 +1064,28 @@ issue_1830_2: {
     }
     expect_stdout: "1"
 }
+
+reassign_const: {
+    options = {
+        cascade: true,
+        sequences: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            const a = 1;
+            a = 2;
+            return a;
+        }
+        console.log(f());
+    }
+    expect: {
+        function f() {
+            const a = 1;
+            return a = 2, a;
+        }
+        console.log(f());
+    }
+    expect_stdout: true
+}
diff --git a/test/compress/reduce_vars.js b/test/compress/reduce_vars.js
index 6726bab5..767311dd 100644
--- a/test/compress/reduce_vars.js
+++ b/test/compress/reduce_vars.js
@@ -41,22 +41,22 @@ reduce_vars: {
         var A = 1;
         (function() {
             console.log(-3);
-            console.log(-4);
+            console.log(A - 5);
         })();
         (function f1() {
             var a = 2;
-            console.log(-3);
+            console.log(a - 5);
             eval("console.log(a);");
         })();
         (function f2(eval) {
             var a = 2;
-            console.log(-3);
+            console.log(a - 5);
             eval("console.log(a);");
         })(eval);
         (function() {
             return "yes";
         })();
-        console.log(2);
+        console.log(A + 1);
     }
     expect_stdout: true
 }
@@ -1732,7 +1732,10 @@ redefine_arguments_3: {
         console.log(function() {
             var arguments;
             return typeof arguments;
-        }(), "number", "undefined");
+        }(), "number", function(x) {
+            var arguments = x;
+            return typeof arguments;
+        }());
     }
     expect_stdout: "object number undefined"
 }
@@ -2122,3 +2125,47 @@ issue_1865: {
     }
     expect_stdout: true
 }
+
+issue_1922_1: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(a) {
+            arguments[0] = 2;
+            return a;
+        }(1));
+    }
+    expect: {
+        console.log(function(a) {
+            arguments[0] = 2;
+            return a;
+        }(1));
+    }
+    expect_stdout: "2"
+}
+
+issue_1922_2: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            var a;
+            eval("a = 1");
+            return a;
+        }(1));
+    }
+    expect: {
+        console.log(function() {
+            var a;
+            eval("a = 1");
+            return a;
+        }(1));
+    }
+    expect_stdout: "1"
+}
diff --git a/test/compress/sequences.js b/test/compress/sequences.js
index 699341c0..3bd0ca35 100644
--- a/test/compress/sequences.js
+++ b/test/compress/sequences.js
@@ -610,3 +610,27 @@ delete_seq_6: {
     }
     expect_stdout: true
 }
+
+reassign_const: {
+    options = {
+        cascade: true,
+        sequences: true,
+        side_effects: true,
+    }
+    input: {
+        function f() {
+            const a = 1;
+            a++;
+            return a;
+        }
+        console.log(f());
+    }
+    expect: {
+        function f() {
+            const a = 1;
+            return a++, a;
+        }
+        console.log(f());
+    }
+    expect_stdout: true
+}