enhance `collapse_vars` (#1862)

- extend expression types
  - `a++`
  - `a=x;`
- extend scan range
  - `for(init;;);`
  - `switch(expr){case expr:}`
  - `a = x; a = a || y;`
- terminate upon `debugger;`

closes #1821
fixes #27
fixes #315
fixes #1858

3 files changed, 554 insertions, 15 deletions

diff --git a/test/compress/collapse_vars.js b/test/compress/collapse_vars.js
index a4c1f9e6..4215cebe 100644
--- a/test/compress/collapse_vars.js
+++ b/test/compress/collapse_vars.js
@@ -68,11 +68,10 @@ collapse_vars_side_effects_1: {
             log(x, s.charAt(i++), y, 7);
         }
         function f4() {
-            var log = console.log.bind(console),
-                i = 10,
+            var i = 10,
                 x = i += 2,
                 y = i += 3;
-            log(x, i += 4, y, i);
+            console.log.bind(console)(x, i += 4, y, i);
         }
         f1(), f2(), f3(), f4();
     }
@@ -671,8 +670,8 @@ collapse_vars_lvalues: {
         function f4(x) { var a = (x -= 3); return x + a; }
         function f5(x) { var w = e1(), v = e2(), c = v = --x; return (w = x) - c; }
         function f6(x) { var w = e1(), v = e2(); return (v = --x) - (w = x); }
-        function f7(x) { var w = e1(), c = e2() - x; return (w = x) - c; }
-        function f8(x) { var w = e1(), v = e2(); return (w = x) - (v - x); }
+        function f7(x) { var w = e1(); return (w = x) - (e2() - x); }
+        function f8(x) { var w = e1(); return (w = x) - (e2() - x); }
         function f9(x) { var w = e1(); return e2() - x - (w = x); }
     }
 }
@@ -703,8 +702,8 @@ collapse_vars_lvalues_drop_assign: {
         function f4(x) { var a = (x -= 3); return x + a; }
         function f5(x) { e1(); var v = e2(), c = v = --x; return x - c; }
         function f6(x) { e1(), e2(); return --x - x; }
-        function f7(x) { e1(); var c = e2() - x; return x - c; }
-        function f8(x) { e1(); var v = e2(); return x - (v - x); }
+        function f7(x) { e1(); return x - (e2() - x); }
+        function f8(x) { e1(); return x - (e2() - x); }
         function f9(x) { e1(); return e2() - x - x; }
     }
 }
@@ -1047,10 +1046,9 @@ collapse_vars_object: {
     }
     expect: {
         function f0(x, y) {
-            var z = x + y;
             return {
                 get b() { return 7; },
-                r: z
+                r: x + y
             };
         }
         function f1(x, y) {
@@ -1677,3 +1675,514 @@ var_defs: {
     }
     expect_stdout: "97"
 }
+
+assignment: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            var a;
+            a = x;
+            return a;
+        }
+    }
+    expect: {
+        function f() {
+            return x;
+        }
+    }
+}
+
+for_init: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        function f(x, y) {
+            var a = x;
+            var b = y;
+            for (a; b;);
+        }
+    }
+    expect: {
+        function f(x, y) {
+            var b = y;
+            for (x; b;);
+        }
+    }
+}
+
+switch_case: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        function f(x, y, z) {
+            var a = x();
+            var b = y();
+            var c = z;
+            switch (a) {
+              default: d();
+              case b: e();
+              case c: f();
+            }
+        }
+    }
+    expect: {
+        function f(x, y, z) {
+            var c = z;
+            switch (x()) {
+              default: d();
+              case y(): e();
+              case c: f();
+            }
+        }
+    }
+}
+
+issue_27: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        (function(jQuery) {
+            var $;
+            $ = jQuery;
+            $("body").addClass("foo");
+        })(jQuery);
+    }
+    expect: {
+        (function(jQuery) {
+            jQuery("body").addClass("foo");
+        })(jQuery);
+    }
+}
+
+modified: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        function f1(b) {
+            var a = b;
+            return b + a;
+        }
+        function f2(b) {
+            var a = b;
+            return b++ + a;
+        }
+        function f3(b) {
+            var a = b++;
+            return b + a;
+        }
+        function f4(b) {
+            var a = b++;
+            return b++ + a;
+        }
+        function f5(b) {
+            var a = function() {
+                return b;
+            }();
+            return b++ + a;
+        }
+        console.log(f1(1), f2(1), f3(1), f4(1), f5(1));
+    }
+    expect: {
+        function f1(b) {
+            return b + b;
+        }
+        function f2(b) {
+            var a = b;
+            return b++ + a;
+        }
+        function f3(b) {
+            var a = b++;
+            return b + a;
+        }
+        function f4(b) {
+            var a = b++;
+            return b++ + a;
+        }
+        function f5(b) {
+            var a = function() {
+                return b;
+            }();
+            return b++ + a;
+        }
+        console.log(f1(1), f2(1), f3(1), f4(1), f5(1));
+    }
+    expect_stdout: "2 2 3 3 2"
+}
+
+issue_1858: {
+    options = {
+        collapse_vars: true,
+        pure_getters: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(x) {
+            var a = {}, b = a.b = x;
+            return a.b + b;
+        }(1));
+    }
+    expect: {
+        console.log(function(x) {
+            var a = {}, b = a.b = x;
+            return a.b + b;
+        }(1));
+    }
+    expect_stdout: "2"
+}
+
+anonymous_function: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        console.log(function f(a) {
+            f ^= 0;
+            return f * a;
+        }(1));
+    }
+    expect: {
+        console.log(function f(a) {
+            f ^= 0;
+            return f * a;
+        }(1));
+    }
+    expect_stdout: true
+}
+
+side_effects_property: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a = [];
+        var b = 0;
+        a[b++] = function() { return 42;};
+        var c = a[b++]();
+        console.log(c);
+    }
+    expect: {
+        var a = [];
+        var b = 0;
+        a[b++] = function() { return 42;};
+        var c = a[b++]();
+        console.log(c);
+    }
+    expect_stdout: true
+}
+
+undeclared: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        function f(x, y) {
+            var a;
+            a = x;
+            b = y;
+            return b + a;
+        }
+    }
+    expect: {
+        function f(x, y) {
+            var a;
+            a = x;
+            b = y;
+            return b + a;
+        }
+    }
+}
+
+ref_scope: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            var a = 1, b = 2, c = 3;
+            var a = c++, b = b /= a;
+            return function() {
+                return a;
+            }() + b;
+        }());
+    }
+    expect: {
+        console.log(function() {
+            var a = 1, b = 2, c = 3;
+            b = b /= a = c++;
+            return function() {
+                return a;
+            }() + b;
+        }());
+    }
+    expect_stdout: true
+}
+
+chained_1: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a = 2;
+        var a = 3 / a;
+        console.log(a);
+    }
+    expect: {
+        var a = 3 / (a = 2);
+        console.log(a);
+    }
+    expect_stdout: true
+}
+
+chained_2: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a;
+        var a = 2;
+        a = 3 / a;
+        console.log(a);
+    }
+    expect: {
+        var a;
+        a = 3 / (a = 2);
+        console.log(a);
+    }
+    expect_stdout: true
+}
+
+chained_3: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(a, b) {
+            var c = a, c = b;
+            b++;
+            return c;
+        }(1, 2));
+    }
+    expect: {
+        console.log(function(a, b) {
+            var c = a, c = b;
+            b++;
+            return c;
+        }(1, 2));
+    }
+    expect_stdout: "2"
+}
+
+boolean_binary_1: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a = 1;
+        a++;
+        (function() {} || a || 3).toString();
+        console.log(a);
+    }
+    expect: {
+        var a = 1;
+        a++;
+        (function() {} || a || 3).toString();
+        console.log(a);
+    }
+    expect_stdout: true
+}
+
+boolean_binary_2: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var c = 0;
+        c += 1;
+        (function() {
+            c = 1 + c;
+        } || 9).toString();
+        console.log(c);
+    }
+    expect: {
+        var c = 0;
+        c += 1;
+        (function() {
+            c = 1 + c;
+        } || 9).toString();
+        console.log(c);
+    }
+    expect_stdout: true
+}
+
+inner_lvalues: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        var a, b = 10;
+        var a = (--b || a || 3).toString(), c = --b + -a;
+        console.log(null, a, b);
+    }
+    expect: {
+        var a, b = 10;
+        var a = (--b || a || 3).toString(), c = --b + -a;
+        console.log(null, a, b);
+    }
+    expect_stdout: true
+}
+
+double_def: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a = x, a = a && y;
+        a();
+    }
+    expect: {
+        var a = x;
+        (a = a && y)();
+    }
+}
+
+toplevel_single_reference: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a;
+        for (var b in x) {
+            var a = b;
+            b(a);
+        }
+    }
+    expect: {
+        var a;
+        for (var b in x)
+            b(a = b);
+    }
+}
+
+unused_orig: {
+    options = {
+        collapse_vars: true,
+        passes: 2,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        var a = 1;
+        console.log(function(b) {
+            var a;
+            var c = b;
+            for (var d in c) {
+                var a = c[0];
+                return --b + a;
+            }
+            try {
+            } catch (e) {
+                --b + a;
+            }
+            a && a.NaN;
+        }([2]), a);
+    }
+    expect: {
+        var a = 1;
+        console.log(function(b) {
+            var c = b;
+            for (var d in c) {
+                var a = c[0];
+                return --b + a;
+            }
+            a && a.NaN;
+        }([2]), a);
+    }
+    expect_stdout: "3 1"
+}
+
+issue_315: {
+    options = {
+        collapse_vars: true,
+        evaluate: true,
+        keep_fargs: false,
+        reduce_vars: true,
+        sequences: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(s) {
+            var w, _i, _len, _ref, _results;
+            _ref = s.trim().split(" ");
+            _results = [];
+            for (_i = 0, _len = _ref.length; _i < _len; _i++) {
+                w = _ref[_i];
+                _results.push(w.toLowerCase());
+            }
+            return _results;
+        }("test"));
+    }
+    expect: {
+        console.log(function() {
+            var w, _i, _len, _ref, _results;
+            for (_results = [], _i = 0, _len = (_ref = "test".trim().split(" ")).length; _i < _len ; _i++)
+                w = _ref[_i], _results.push(w.toLowerCase());
+            return _results;
+        }());
+    }
+    expect_stdout: true
+}
+
+lvalues_def: {
+    options = {
+        collapse_vars: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        var a = 0, b = 1;
+        var a = b++, b = +function() {}();
+        a && a[a++];
+        console.log(a, b);
+    }
+    expect: {
+        var a = 0, b = 1;
+        var a = b++, b = +void 0;
+        a && a[a++];
+        console.log(a, b);
+    }
+    expect_stdout: true
+}
+
+compound_assignment: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var a;
+        a = 1;
+        a += a + 2;
+        console.log(a);
+    }
+    expect: {
+        var a;
+        a = 1;
+        a += a + 2;
+        console.log(a);
+    }
+    expect_stdout: "4"
+}
diff --git a/test/compress/drop-unused.js b/test/compress/drop-unused.js
index c702cfaf..ddf90bfa 100644
--- a/test/compress/drop-unused.js
+++ b/test/compress/drop-unused.js
@@ -1114,3 +1114,36 @@ issue_1838: {
         "}",
     ]
 }
+
+var_catch_toplevel: {
+    options = {
+        conditionals: true,
+        negate_iife: true,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            a--;
+            try {
+                a++;
+            } catch(a) {
+                if (a) var a;
+                var a = 10;
+            }
+        }
+        f();
+    }
+    expect: {
+        !function() {
+            a--;
+            try {
+                a++;
+            } catch(a) {
+                var a;
+            }
+        }();
+    }
+}
diff --git a/test/compress/issue-1609.js b/test/compress/issue-1609.js
index da4b54a2..dffa54a5 100644
--- a/test/compress/issue-1609.js
+++ b/test/compress/issue-1609.js
@@ -18,9 +18,7 @@ chained_evaluation_1: {
     expect: {
         (function() {
             (function() {
-                var c;
-                c = f(1);
-                c.bar = 1;
+                f(1).bar = 1;
             })();
         })();
     }
@@ -46,9 +44,8 @@ chained_evaluation_2: {
     expect: {
         (function() {
             (function() {
-                var c, b = "long piece of string";
-                c = f(b);
-                c.bar = b;
+                var b = "long piece of string";
+                f(b).bar = b;
             })();
         })();
     }