[Pkg-javascript-commits] [uglifyjs] 13/50: fix invalid transform on `const` (#1919)

[Jonas Smedegaard]

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js pushed a commit to branch master
in repository uglifyjs.

commit aa7e8783f84d119f0226f20d019d6f81f325847f
Author: Alex Lam S.L <alexlamsl at gmail.com>
Date:   Fri May 12 04:51:44 2017 +0800

    fix invalid transform on `const` (#1919)
    
    - preserve (re)assignment to `const` for runtime error
    - suppress `cascade` on `const`, as runtime behaviour is ill-defined
---
 lib/compress.js                | 12 ++++++++++-
 test/compress/collapse_vars.js | 46 ++++++++++++++++++++++++++++++++++++++++++
 test/compress/drop-unused.js   | 25 +++++++++++++++++++++++
 test/compress/sequences.js     | 24 ++++++++++++++++++++++
 4 files changed, 106 insertions(+), 1 deletion(-)

diff --git a/lib/compress.js b/lib/compress.js
index 8454a43..f9dcd0f 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -440,6 +440,14 @@ 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 +1917,7 @@ 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 +3075,8 @@ 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 2264783..53ae8f4 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 9d37dc7..7a2f86a 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/sequences.js b/test/compress/sequences.js
index 699341c..3bd0ca3 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
+}

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