enhance `booleans` (#5043)

2 files changed, 71 insertions, 9 deletions

diff --git a/lib/compress.js b/lib/compress.js
index a93e34fd..ea431f13 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -8239,7 +8239,10 @@ merge(Compressor.prototype, {
     }
 
     function mark_duplicate_condition(compressor, node) {
-        var level = 0, child, parent = compressor.self();
+        var child;
+        var level = 0;
+        var negated = false;
+        var parent = compressor.self();
         if (!is_statement(parent)) while (true) {
             child = parent;
             parent = compressor.parent(level++);
@@ -8248,16 +8251,24 @@ merge(Compressor.prototype, {
                 if (!lazy_op[op]) return;
                 var left = parent.left;
                 if (left === child) continue;
-                if (node.equivalent_to(left)) node[op == "&&" ? "truthy" : "falsy"] = true;
+                if (match(left)) switch (op) {
+                  case "&&":
+                    node[negated ? "falsy" : "truthy"] = true;
+                    break;
+                  case "||":
+                  case "??":
+                    node[negated ? "truthy" : "falsy"] = true;
+                    break;
+                }
             } else if (parent instanceof AST_Conditional) {
                 var cond = parent.condition;
                 if (cond === child) continue;
-                if (node.equivalent_to(cond)) switch (child) {
+                if (match(cond)) switch (child) {
                   case parent.consequent:
-                    node.truthy = true;
+                    node[negated ? "falsy" : "truthy"] = true;
                     break;
                   case parent.alternative:
-                    node.falsy = true;
+                    node[negated ? "truthy" : "falsy"] = true;
                     break;
                 }
             } else if (parent instanceof AST_Exit) {
@@ -8277,17 +8288,26 @@ merge(Compressor.prototype, {
             if (parent instanceof AST_BlockStatement) {
                 if (parent.body[0] === child) continue;
             } else if (parent instanceof AST_If) {
-                if (node.equivalent_to(parent.condition)) switch (child) {
+                if (match(parent.condition)) switch (child) {
                   case parent.body:
-                    node.truthy = true;
+                    node[negated ? "falsy" : "truthy"] = true;
                     break;
                   case parent.alternative:
-                    node.falsy = true;
+                    node[negated ? "truthy" : "falsy"] = true;
                     break;
                 }
             }
             return;
         }
+
+        function match(cond) {
+            if (node.equivalent_to(cond)) return true;
+            if (!(cond instanceof AST_UnaryPrefix)) return false;
+            if (cond.operator != "!") return false;
+            if (!node.equivalent_to(cond.expression)) return false;
+            negated = true;
+            return true;
+        }
     }
 
     OPT(AST_If, function(self, compressor) {
diff --git a/test/compress/booleans.js b/test/compress/booleans.js
index 280a355d..17b0f15e 100644
--- a/test/compress/booleans.js
+++ b/test/compress/booleans.js
@@ -406,6 +406,27 @@ conditional_chain: {
     expect_stdout: "PASS"
 }
 
+negated_if: {
+    options = {
+        booleans: true,
+        conditionals: true,
+        side_effects: true,
+    }
+    input: {
+        console.log(function(a) {
+            if (!a)
+                return a ? "FAIL" : "PASS";
+        }(!console));
+    }
+    expect: {
+        console.log(function(a) {
+            if (!a)
+                return "PASS";
+        }(!console));
+    }
+    expect_stdout: "PASS"
+}
+
 issue_3465_1: {
     options = {
         booleans: true,
@@ -635,7 +656,7 @@ issue_5028_3: {
     expect_stdout: "-1"
 }
 
-issue_5041: {
+issue_5041_1: {
     options = {
         booleans: true,
         conditionals: true,
@@ -655,3 +676,24 @@ issue_5041: {
     }
     expect_stdout: "PASS"
 }
+
+issue_5041_2: {
+    options = {
+        booleans: true,
+        conditionals: true,
+    }
+    input: {
+        var a;
+        if (!a)
+            if (a = 42)
+                if (a)
+                    console.log("PASS");
+                else
+                    console.log("FAIL");
+    }
+    expect: {
+        var a;
+        a || (a = 42) && (a ? console.log("PASS") : console.log("FAIL"));
+    }
+    expect_stdout: "PASS"
+}