fix corner cases in collapse_vars (#5321)

fixes #5319

lib/compress.js

@@ -2028,19 +2028,31 @@ Compressor.prototype.compress = function(node) {
                         line: node.start.line,
                         col: node.start.col,
                     });
-                    if (candidate.TYPE == "Binary") return make_node(AST_Assign, candidate, {
+                    if (candidate.TYPE == "Binary") {
+                        update_symbols(candidate, node);
+                        return make_node(AST_Assign, candidate, {
                             operator: "=",
                             left: candidate.right.left,
-                        right: make_node(AST_Conditional, candidate, {
+                            right: candidate.operator == "&&" ? make_node(AST_Conditional, candidate, {
-                            condition: candidate.operator == "&&" ? candidate.left : candidate.left.negate(compressor),
+                                condition: candidate.left,
                                 consequent: candidate.right.right,
                                 alternative: node,
+                            }) : make_node(AST_Conditional, candidate, {
+                                condition: candidate.left,
+                                consequent: node,
+                                alternative: candidate.right.right,
                             }),
                         });
+                    }
                     if (candidate instanceof AST_UnaryPostfix) return make_node(AST_UnaryPrefix, candidate, {
                         operator: candidate.operator,
                         expression: lhs.fixed && lhs.definition().fixed ? lhs.fixed.to_prefix() : lhs,
                     });
+                    if (candidate instanceof AST_UnaryPrefix) {
+                        clear_write_only(candidate);
+                        return candidate;
+                    }
+                    update_symbols(rvalue, node);
                     if (candidate instanceof AST_VarDef) {
                         var def = candidate.name.definition();
                         if (def.references.length - def.replaced == 1 && !compressor.exposed(def)) {
@@ -2053,7 +2065,7 @@ Compressor.prototype.compress = function(node) {
                             right: rvalue,
                         });
                     }
-                    clear_write_only(candidate);
+                    clear_write_only(rvalue);
                     var assign = candidate.clone();
                     assign.right = rvalue;
                     return assign;
@@ -3011,6 +3023,14 @@ Compressor.prototype.compress = function(node) {
                 }
             }
 
+            function update_symbols(value, node) {
+                var scope = node.scope || find_scope(scanner) || block_scope;
+                value.walk(new TreeWalker(function(node) {
+                    if (node instanceof AST_BlockScope) return true;
+                    if (node instanceof AST_Symbol) node.scope = scope;
+                }));
+            }
+
             function may_be_global(node) {
                 if (node instanceof AST_SymbolRef) {
                     node = node.fixed_value();
@@ -5927,16 +5947,6 @@ Compressor.prototype.compress = function(node) {
         var references = Object.create(null);
         var prev = Object.create(null);
         var tw = new TreeWalker(function(node, descend) {
-            if (node.variables) {
-                if (node instanceof AST_BlockStatement) {
-                    var save_scope = segment.scope;
-                    segment.scope = node;
-                    descend();
-                    segment.scope = save_scope;
-                    return true;
-                }
-                segment.scope = node;
-            }
             if (node instanceof AST_Assign) {
                 var lhs = node.left;
                 var rhs = node.right;
@@ -6308,7 +6318,6 @@ Compressor.prototype.compress = function(node) {
                 var refs = references[def.id];
                 if (!refs) return;
                 if (refs.start.block !== seg.block) return references[def.id] = false;
-                sym.scope = seg.scope;
                 refs.push(sym);
                 refs.end = seg;
                 if (def.id in prev) {
@@ -6323,7 +6332,6 @@ Compressor.prototype.compress = function(node) {
                 return references[def.id] = false;
             } else {
                 var refs = declarations.get(def.id) || [];
-                sym.scope = seg.scope;
                 refs.push(sym);
                 references[def.id] = refs;
                 if (!read) {

test/compress/collapse_vars.js

@@ -9014,6 +9014,27 @@ collapse_and_assign: {
     expect_stdout: "PASS"
 }
 
+collapse_and_assign_property: {
+    options = {
+        collapse_vars: true,
+        pure_getters: "strict",
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function f() {
+            f && (f.p = "PASS");
+            return f.p;
+        }());
+    }
+    expect: {
+        console.log(function f() {
+            return f.p = f ? "PASS" : f.p;
+        }());
+    }
+    expect_stdout: "PASS"
+}
+
 collapse_or_assign: {
     options = {
         collapse_vars: true,
@@ -9031,7 +9052,7 @@ collapse_or_assign: {
         var a = {
             p: "PASS",
         };
-        log(a = !a.q ? a.p : a);
+        log(a = a.q ? a: a.p);
     }
     expect_stdout: "PASS"
 }