enable `collapse_vars` & `reduce_vars` by default

- fix corner cases in `const` optimisation
- deprecate `/*@const*/`

fixes #1497
closes #1498

5 files changed, 46 insertions, 6 deletions

diff --git a/test/compress/const.js b/test/compress/const.js
index dd175fcc..f1f13f49 100644
--- a/test/compress/const.js
+++ b/test/compress/const.js
@@ -12,6 +12,7 @@ issue_1191: {
         join_vars     : true,
         sequences     : false,
         collapse_vars : false,
+        reduce_vars   : true,
     }
     input: {
         function foo(rot) {
@@ -43,6 +44,7 @@ issue_1194: {
         join_vars     : true,
         sequences     : false,
         collapse_vars : false,
+        reduce_vars   : true,
     }
     input: {
         function f1() {const a = "X"; return a + a;}
@@ -70,6 +72,7 @@ issue_1396: {
         join_vars     : true,
         sequences     : false,
         collapse_vars : false,
+        reduce_vars   : true,
     }
     input: {
         function foo(a) {
@@ -140,6 +143,7 @@ regexp_literal_not_const: {
         join_vars     : true,
         sequences     : false,
         collapse_vars : false,
+        reduce_vars   : true,
     }
     input: {
         (function(){
diff --git a/test/compress/dead-code.js b/test/compress/dead-code.js
index c83f2040..2596e80e 100644
--- a/test/compress/dead-code.js
+++ b/test/compress/dead-code.js
@@ -94,7 +94,8 @@ dead_code_const_declaration: {
         loops        : true,
         booleans     : true,
         conditionals : true,
-        evaluate     : true
+        evaluate     : true,
+        reduce_vars  : true,
     };
     input: {
         var unused;
@@ -119,7 +120,8 @@ dead_code_const_annotation: {
         loops        : true,
         booleans     : true,
         conditionals : true,
-        evaluate     : true
+        evaluate     : true,
+        reduce_vars  : true,
     };
     input: {
         var unused;
@@ -167,7 +169,8 @@ dead_code_const_annotation_complex_scope: {
         loops        : true,
         booleans     : true,
         conditionals : true,
-        evaluate     : true
+        evaluate     : true,
+        reduce_vars  : true,
     };
     input: {
         var unused_var;
@@ -201,6 +204,5 @@ dead_code_const_annotation_complex_scope: {
         var beef = 'good';
         var meat = 'beef';
         var pork = 'bad';
-        'good' === pork && console.log('reached, not const');
     }
 }
diff --git a/test/compress/drop-unused.js b/test/compress/drop-unused.js
index f5a88f21..c1ca1b55 100644
--- a/test/compress/drop-unused.js
+++ b/test/compress/drop-unused.js
@@ -648,3 +648,34 @@ drop_value: {
         foo(), bar();
     }
 }
+
+const_assign: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            const b = 2;
+            return 1 + b;
+        }
+
+        function g() {
+            const b = 2;
+            b = 3;
+            return 1 + b;
+        }
+    }
+    expect: {
+        function f() {
+            return 3;
+        }
+
+        function g() {
+            const b = 2;
+            b = 3;
+            return 1 + b;
+        }
+    }
+}
diff --git a/test/compress/evaluate.js b/test/compress/evaluate.js
index f88bc538..ae5e58d6 100644
--- a/test/compress/evaluate.js
+++ b/test/compress/evaluate.js
@@ -602,6 +602,7 @@ unsafe_prototype_function: {
 call_args: {
     options = {
         evaluate: true,
+        reduce_vars: true,
     }
     input: {
         const a = 1;
diff --git a/test/compress/issue-1041.js b/test/compress/issue-1041.js
index 9dd176fd..cdbc22cc 100644
--- a/test/compress/issue-1041.js
+++ b/test/compress/issue-1041.js
@@ -13,7 +13,8 @@ const_declaration: {
 
 const_pragma: {
     options = {
-        evaluate: true
+        evaluate: true,
+        reduce_vars: true,
     };
 
     input: {
@@ -27,7 +28,8 @@ const_pragma: {
 // for completeness' sake
 not_const: {
     options = {
-        evaluate: true
+        evaluate: true,
+        reduce_vars: true,
     };
 
     input: {