fix various corner cases (#3123)

test/compress/collapse_vars.js

@@ -4056,6 +4056,36 @@ replace_all_var: {
     expect_stdout: "PASS"
 }
 
+replace_all_var_scope: {
+    rename = true;
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    mangle = {}
+    input: {
+        var a = 100, b = 10;
+        (function(r, a) {
+            switch (~a) {
+            case (b += a):
+            case a++:
+            }
+        })(--b, a);
+        console.log(a, b);
+    }
+    expect: {
+        var a = 100, b = 10;
+        (function(c, o) {
+            switch (~a) {
+            case (b += a):
+            case o++:
+            }
+        })(--b, a);
+        console.log(a, b);
+    }
+    expect_stdout: "100 109"
+}
+
 cascade_statement: {
     options = {
         collapse_vars: true,

test/compress/reduce_vars.js

@@ -5998,3 +5998,35 @@ issue_3113_5: {
         "1",
     ]
 }
+
+conditional_nested: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+    }
+    input: {
+        var a = 1, b = 0;
+        (function f(c) {
+            function g() {
+                c && (c.a = 0);
+                c && (c.a = 0);
+                c && (c[b++] *= 0);
+            }
+            g(a-- && f(g(c = 42)));
+        })();
+        console.log(b);
+    }
+    expect: {
+        var a = 1, b = 0;
+        (function f(c) {
+            function g() {
+                c && (c.a = 0);
+                c && (c.a = 0);
+                c && (c[b++] *= 0);
+            }
+            g(a-- && f(g(c = 42)));
+        })();
+        console.log(b);
+    }
+    expect_stdout: "2"
+}