handle overlapped variable definitions (#1691)

Process variable definitions with or without assigned values against:
- `arguments`
- named function arguments
- multiple definitions within same scope

Essentially demote variable declarations with no value assignments.

Also fixed invalid use of `AST_VarDef` over `arguments` - should use a member of `AST_SymbolDeclaration` instead.

1 files changed, 286 insertions, 3 deletions

diff --git a/test/compress/reduce_vars.js b/test/compress/reduce_vars.js
index f4dd68d2..87942ab9 100644
--- a/test/compress/reduce_vars.js
+++ b/test/compress/reduce_vars.js
@@ -425,7 +425,7 @@ iife_new: {
     expect_stdout: true
 }
 
-multi_def: {
+multi_def_1: {
     options = {
         evaluate: true,
         reduce_vars: true,
@@ -435,7 +435,7 @@ multi_def: {
             if (a)
                 var b = 1;
             else
-                var b = 2
+                var b = 2;
             console.log(b + 1);
         }
     }
@@ -444,7 +444,7 @@ multi_def: {
             if (a)
                 var b = 1;
             else
-                var b = 2
+                var b = 2;
             console.log(b + 1);
         }
     }
@@ -479,6 +479,33 @@ multi_def_2: {
     }
 }
 
+multi_def_3: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+    }
+    input: {
+        function f(a) {
+            var b = 2;
+            if (a)
+                var b;
+            else
+                var b;
+            console.log(b + 1);
+        }
+    }
+    expect: {
+        function f(a) {
+            var b = 2;
+            if (a)
+                var b;
+            else
+                var b;
+            console.log(3);
+        }
+    }
+}
+
 use_before_var: {
     options = {
         evaluate: true,
@@ -1571,3 +1598,259 @@ unary_delete: {
     }
     expect_stdout: true
 }
+
+redefine_arguments_1: {
+    options = {
+        evaluate: true,
+        keep_fargs: false,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            var arguments;
+            return typeof arguments;
+        }
+        function g() {
+            var arguments = 42;
+            return typeof arguments;
+        }
+        function h(x) {
+            var arguments = x;
+            return typeof arguments;
+        }
+        console.log(f(), g(), h());
+    }
+    expect: {
+        function f() {
+            var arguments;
+            return typeof arguments;
+        }
+        function g() {
+            return"number";
+        }
+        function h(x) {
+            var arguments = x;
+            return typeof arguments;
+        }
+        console.log(f(), g(), h());
+    }
+    expect_stdout: "object number undefined"
+}
+
+redefine_arguments_2: {
+    options = {
+        evaluate: true,
+        keep_fargs: false,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            var arguments;
+            return typeof arguments;
+        }
+        function g() {
+            var arguments = 42;
+            return typeof arguments;
+        }
+        function h(x) {
+            var arguments = x;
+            return typeof arguments;
+        }
+        console.log(f(), g(), h());
+    }
+    expect: {
+        console.log(function() {
+            var arguments;
+            return typeof arguments;
+        }(), function() {
+            return"number";
+        }(), function(x) {
+            var arguments = x;
+            return typeof arguments;
+        }());
+    }
+    expect_stdout: "object number undefined"
+}
+
+redefine_arguments_3: {
+    options = {
+        evaluate: true,
+        keep_fargs: false,
+        passes: 3,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            var arguments;
+            return typeof arguments;
+        }
+        function g() {
+            var arguments = 42;
+            return typeof arguments;
+        }
+        function h(x) {
+            var arguments = x;
+            return typeof arguments;
+        }
+        console.log(f(), g(), h());
+    }
+    expect: {
+        console.log(function() {
+            var arguments;
+            return typeof arguments;
+        }(), "number", "undefined");
+    }
+    expect_stdout: "object number undefined"
+}
+
+redefine_farg_1: {
+    options = {
+        evaluate: true,
+        keep_fargs: false,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        function f(a) {
+            var a;
+            return typeof a;
+        }
+        function g(a) {
+            var a = 42;
+            return typeof a;
+        }
+        function h(a, b) {
+            var a = b;
+            return typeof a;
+        }
+        console.log(f([]), g([]), h([]));
+    }
+    expect: {
+        function f(a) {
+            var a;
+            return typeof a;
+        }
+        function g() {
+            return"number";
+        }
+        function h(a, b) {
+            var a = b;
+            return typeof a;
+        }
+        console.log(f([]), g([]), h([]));
+    }
+    expect_stdout: "object number undefined"
+}
+
+redefine_farg_2: {
+    options = {
+        evaluate: true,
+        keep_fargs: false,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f(a) {
+            var a;
+            return typeof a;
+        }
+        function g(a) {
+            var a = 42;
+            return typeof a;
+        }
+        function h(a, b) {
+            var a = b;
+            return typeof a;
+        }
+        console.log(f([]), g([]), h([]));
+    }
+    expect: {
+        console.log(function(a) {
+            var a;
+            return typeof a;
+        }([]), function() {
+            return "number";
+        }(),function(a, b) {
+            var a = b;
+            return typeof a;
+        }([]));
+    }
+    expect_stdout: "object number undefined"
+}
+
+redefine_farg_3: {
+    options = {
+        evaluate: true,
+        keep_fargs: false,
+        passes: 3,
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function f(a) {
+            var a;
+            return typeof a;
+        }
+        function g(a) {
+            var a = 42;
+            return typeof a;
+        }
+        function h(a, b) {
+            var a = b;
+            return typeof a;
+        }
+        console.log(f([]), g([]), h([]));
+    }
+    expect: {
+        console.log(function(a) {
+            var a;
+            return typeof a;
+        }([]), "number", function(a) {
+            var a = void 0;
+            return typeof a;
+        }([]));
+    }
+    expect_stdout: "object number undefined"
+}
+
+delay_def: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            return a;
+            var a;
+        }
+        function g() {
+            return a;
+            var a = 1;
+        }
+        console.log(f(), g());
+    }
+    expect: {
+        function f() {
+            return a;
+            var a;
+        }
+        function g() {
+            return a;
+            var a = 1;
+        }
+        console.log(f(), g());
+    }
+    expect_stdout: true
+}