fix corner case in conditionals (#5674)

fixes #5673

Author: alexlamsl

Diff for: lib/compress.js

@@ -1828,6 +1828,29 @@ Compressor.prototype.compress = function(node) {
         return wrap ? make_sequence(orig, [ make_node(AST_Number, orig, { value: 0 }), val ]) : val;
     }
 
+    function merge_expression(base, target, scope) {
+        var fixed_by_id = new Dictionary();
+        base.walk(new TreeWalker(function(node) {
+            if (!(node instanceof AST_SymbolRef)) return;
+            var def = node.definition();
+            if (scope && def.scope.resolve() !== scope) return;
+            var fixed = node.fixed;
+            if (!fixed || !fixed_by_id.has(def.id)) {
+                fixed_by_id.set(def.id, fixed);
+            } else if (fixed_by_id.get(def.id) !== fixed) {
+                fixed_by_id.set(def.id, false);
+            }
+        }));
+        if (fixed_by_id.size() > 0) target.walk(new TreeWalker(function(node) {
+            if (!(node instanceof AST_SymbolRef)) return;
+            var def = node.definition();
+            var fixed = node.fixed;
+            if (!fixed || !fixed_by_id.has(def.id)) return;
+            if (fixed_by_id.get(def.id) !== fixed) node.fixed = false;
+        }));
+        return target;
+    }
+
     function merge_sequence(array, node) {
         if (node instanceof AST_Sequence) {
             [].push.apply(array, node.expressions);
@@ -3813,25 +3836,7 @@ Compressor.prototype.compress = function(node) {
                   case 2:
                     value = value.tail_node();
                 }
-                var fixed_by_id = new Dictionary();
-                value.walk(new TreeWalker(function(node) {
-                    if (!(node instanceof AST_SymbolRef)) return;
-                    var def = node.definition();
-                    if (def.scope.resolve() !== scope) return;
-                    var fixed = node.fixed;
-                    if (!fixed || !fixed_by_id.has(def.id)) {
-                        fixed_by_id.set(def.id, fixed);
-                    } else if (fixed_by_id.get(def.id) !== fixed) {
-                        fixed_by_id.set(def.id, false);
-                    }
-                }));
-                if (fixed_by_id.size() > 0) jump.value.walk(new TreeWalker(function(node) {
-                    if (!(node instanceof AST_SymbolRef)) return;
-                    var def = node.definition();
-                    var fixed = node.fixed;
-                    if (!fixed || !fixed_by_id.has(def.id)) return;
-                    if (fixed_by_id.get(def.id) !== fixed) node.fixed = false;
-                }));
+                merge_expression(value, jump.value, scope);
             }
 
             function next_index(i) {
@@ -12933,7 +12938,7 @@ Compressor.prototype.compress = function(node) {
                     right: fuse(consequent, seq_tail, "condition"),
                 }),
                 consequent: seq_tail.consequent,
-                alternative: alternative,
+                alternative: merge_expression(seq_tail.alternative, alternative),
             });
         }
         // x ? (y ? a : b) : a ---> !x || y ? a : b
@@ -12945,7 +12950,7 @@ Compressor.prototype.compress = function(node) {
                     operator: "||",
                     right: fuse(consequent, seq_tail, "condition"),
                 }),
-                consequent: alternative,
+                consequent: merge_expression(seq_tail.consequent, alternative),
                 alternative: seq_tail.alternative,
             });
         }
@@ -12958,7 +12963,7 @@ Compressor.prototype.compress = function(node) {
                     operator: "||",
                     right: fuse(alternative, alt_tail, "condition"),
                 }),
-                consequent: consequent,
+                consequent: merge_expression(consequent, alt_tail.consequent),
                 alternative: alt_tail.alternative,
             });
         }
@@ -12972,7 +12977,7 @@ Compressor.prototype.compress = function(node) {
                     right: fuse(alternative, alt_tail, "condition"),
                 }),
                 consequent: alt_tail.consequent,
-                alternative: consequent,
+                alternative: merge_expression(consequent, alt_tail.alternative),
             });
         }
         // x ? y && a : a ---> (!x || y) && a
@@ -12986,7 +12991,7 @@ Compressor.prototype.compress = function(node) {
                     left: negated,
                     right: fuse(consequent, seq_tail, "left"),
                 }),
-                right: alternative,
+                right: merge_expression(seq_tail.right, alternative),
             }).optimize(compressor);
         }
         // x ? y || a : a ---> x && y || a
@@ -13000,7 +13005,7 @@ Compressor.prototype.compress = function(node) {
                     left: condition,
                     right: fuse(consequent, seq_tail, "left"),
                 }),
-                right: alternative,
+                right: merge_expression(seq_tail.right, alternative),
             }).optimize(compressor);
         }
         // x ? a : y && a ---> (x || y) && a
@@ -13014,7 +13019,7 @@ Compressor.prototype.compress = function(node) {
                     left: condition,
                     right: fuse(alternative, alt_tail, "left"),
                 }),
-                right: consequent,
+                right: merge_expression(consequent, alt_tail.right),
             }).optimize(compressor);
         }
         // x ? a : y || a ---> !x && y || a
@@ -13028,7 +13033,7 @@ Compressor.prototype.compress = function(node) {
                     left: negated,
                     right: fuse(alternative, alt_tail, "left"),
                 }),
-                right: consequent,
+                right: merge_expression(consequent, alt_tail.right),
             }).optimize(compressor);
         }
         var in_bool = compressor.option("booleans") && compressor.in_boolean_context();

Diff for: test/compress/conditionals.js

@@ -2928,3 +2928,45 @@ issue_5666_2: {
     }
     expect_stdout: "NaN"
 }
+
+issue_5673_1: {
+    options = {
+        conditionals: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS", b = null;
+        console.log(function(c) {
+            return c || (b ? c : (c = a) && c);
+        }());
+    }
+    expect: {
+        var a = "PASS", b = null;
+        console.log(function(c) {
+            return c || (b || (c = a)) && c;
+        }());
+    }
+    expect_stdout: "PASS"
+}
+
+issue_5673_2: {
+    options = {
+        conditionals: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        var a = "PASS";
+        console.log(function(b) {
+            return (b = a) ? b : (b = a) && b;
+        }());
+    }
+    expect: {
+        var a = "PASS";
+        console.log(function(b) {
+            return ((b = a) || (b = a)) && b;
+        }());
+    }
+    expect_stdout: "PASS"
+}