enhance `collapse_vars` (#4735)

6 files changed, 87 insertions, 25 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 6a59a9d5..c9ba218d 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2068,8 +2068,9 @@ merge(Compressor.prototype, {
                 if (node instanceof AST_ObjectIdentity) return symbol_in_lvalues(node, parent);
                 if (node instanceof AST_PropAccess) {
                     var exp = node.expression;
-                    return side_effects || !value_def && exp.may_throw_on_access(compressor)
-                        || exp instanceof AST_SymbolRef && is_arguments(exp.definition());
+                    return side_effects
+                        || exp instanceof AST_SymbolRef && is_arguments(exp.definition())
+                        || !value_def && (in_try || !lhs_local) && exp.may_throw_on_access(compressor);
                 }
                 if (node instanceof AST_Spread) return true;
                 if (node instanceof AST_SymbolRef) {
diff --git a/test/compress/classes.js b/test/compress/classes.js
index 82c6f30e..93819bfa 100644
--- a/test/compress/classes.js
+++ b/test/compress/classes.js
@@ -620,11 +620,10 @@ collapse_rhs: {
     expect: {
         "use strict";
         var a = "FAIL";
-        a = "PASS";
         class A {
             p = "PASS";
         }
-        console.log(a);
+        console.log(a = "PASS");
     }
     expect_stdout: "PASS"
     node_version: ">=12"
diff --git a/test/compress/collapse_vars.js b/test/compress/collapse_vars.js
index 6e82e8b0..dcc87397 100644
--- a/test/compress/collapse_vars.js
+++ b/test/compress/collapse_vars.js
@@ -958,8 +958,7 @@ collapse_vars_misc: {
     }
     expect: {
         function f0(o, a, h) {
-            var b = 3 - a;
-            return o.run(b)[7] = h;
+            return o.run(3 - a)[7] = h;
         }
         function f1(x) { return 5 - x }
         function f2(x) { return foo() / (5 - x) }
@@ -2276,8 +2275,8 @@ var_defs: {
     }
     expect: {
         var f1 = function(x, y) {
-            var r = x + y, z = r * r - r, b = 7;
-            console.log(z + b);
+            var r = x + y;
+            console.log(r * r - r + 7);
         };
         f1("1", 0);
     }
@@ -2907,8 +2906,7 @@ issue_2187_1: {
         var a = 1;
         !function(foo) {
             foo();
-            var a = 2;
-            console.log(a);
+            console.log(2);
         }(function() {
             console.log(a);
         });
@@ -6961,8 +6959,7 @@ sequence_in_iife_2: {
     }
     expect: {
         var a = "foo", b = 42;
-        b = a;
-        console.log(a, b);
+        console.log(a, b = a);
     }
     expect_stdout: "foo foo"
 }
@@ -8804,3 +8801,59 @@ issue_4732_2: {
     }
     expect_stdout: "PASS"
 }
+
+dot_in_try: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var o, a = 6, b = 7, c;
+        try {
+            c = a * b;
+            o.p(c);
+        } catch (e) {
+            console.log(c);
+        }
+    }
+    expect: {
+        var o, a = 6, b = 7, c;
+        try {
+            c = a * b;
+            o.p(c);
+        } catch (e) {
+            console.log(c);
+        }
+    }
+    expect_stdout: "42"
+}
+
+dot_non_local: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        var o, a = 6, b = 7, c;
+        function f() {
+            c = a * b;
+            o.p(c);
+        }
+        try {
+            f();
+        } catch (e) {
+            console.log(c);
+        }
+    }
+    expect: {
+        var o, a = 6, b = 7, c;
+        function f() {
+            c = a * b;
+            o.p(c);
+        }
+        try {
+            f();
+        } catch (e) {
+            console.log(c);
+        }
+    }
+    expect_stdout: "42"
+}
diff --git a/test/compress/evaluate.js b/test/compress/evaluate.js
index 597c7c87..2c978fff 100644
--- a/test/compress/evaluate.js
+++ b/test/compress/evaluate.js
@@ -2726,8 +2726,8 @@ issue_3944: {
     }
     expect: {
         void function f() {
-            while (a = 0 == (a = void 0), console.log(a), void 0);
-            var a;
+            while (b = void 0, b = console.log(0 == (b && b.p)), void 0);
+            var b;
             f;
         }();
     }
diff --git a/test/compress/functions.js b/test/compress/functions.js
index 98dfc4d8..30779c15 100644
--- a/test/compress/functions.js
+++ b/test/compress/functions.js
@@ -2492,14 +2492,14 @@ issue_3297_3: {
     input: {
         function function1(session) {
             var public = {
-                processBulk: processBulk
+                processBulk: processBulk,
             };
             return public;
             function processBulk(bulk) {
                 var subparam1 = session();
                 function processOne(param1) {
                     var param2 = {
-                        subparam1: subparam1
+                        subparam1: subparam1,
                     };
                     doProcessOne({
                         param1: param1,
@@ -2525,18 +2525,18 @@ issue_3297_3: {
             return {
                 processBulk: function n(o) {
                     var r, t, u = c();
-                    o && 0 < o.length && (r = {
-                        param1: o.shift(),
-                        param2: {
-                            subparam1: u
-                        }
-                    },
+                    o && 0 < o.length && (r = o.shift(),
                     t = function() {
                         n(o);
                     },
-                    console.log(JSON.stringify(r)),
+                    console.log(JSON.stringify({
+                        param1: r,
+                        param2: {
+                            subparam1: u,
+                        },
+                    })),
                     t());
-                }
+                },
             };
         }
         function1(function() {
diff --git a/test/compress/sequences.js b/test/compress/sequences.js
index a9dbc707..79b308b5 100644
--- a/test/compress/sequences.js
+++ b/test/compress/sequences.js
@@ -663,12 +663,21 @@ side_effects_cascade_1: {
             if (a < 0) a = 0;
             b.a = a;
         }
+        var m = {}, n = {};
+        f(13, m);
+        f("foo", n);
+        console.log(m.a, n.a);
     }
     expect: {
         function f(a, b) {
-            (a -= 42) < 0 && (a = 0), b.a = a;
+            b.a = a = (a -= 42) < 0 ? 0 : a;
         }
+        var m = {}, n = {};
+        f(13, m),
+        f("foo", n),
+        console.log(m.a, n.a);
     }
+    expect_stdout: "0 NaN"
 }
 
 side_effects_cascade_2: {