avoid confusion of NaN & Infinity with catch symbol of the same name (#1763)

fixes #1760
fixes #1761

lib/compress.js

@@ -409,6 +409,18 @@ merge(Compressor.prototype, {
         }
     });
 
+    function find_variable(compressor, name) {
+        var scope, i = 0;
+        while (scope = compressor.parent(i++)) {
+            if (scope instanceof AST_Scope) break;
+            if (scope instanceof AST_Catch) {
+                scope = scope.argname.definition().scope;
+                break;
+            }
+        }
+        return scope.find_variable(name);
+    }
+
     function make_node(ctor, orig, props) {
         if (!props) props = {};
         if (orig) {
@@ -3517,12 +3529,11 @@ merge(Compressor.prototype, {
 
     OPT(AST_Undefined, function(self, compressor){
         if (compressor.option("unsafe")) {
-            var scope = compressor.find_parent(AST_Scope);
+            var undef = find_variable(compressor, "undefined");
-            var undef = scope.find_variable("undefined");
             if (undef) {
                 var ref = make_node(AST_SymbolRef, self, {
                     name   : "undefined",
-                    scope  : scope,
+                    scope  : undef.scope,
                     thedef : undef
                 });
                 ref.is_undefined = true;
@@ -3538,8 +3549,7 @@ merge(Compressor.prototype, {
     });
 
     OPT(AST_Infinity, function(self, compressor){
-        var retain = compressor.option("keep_infinity")
+        var retain = compressor.option("keep_infinity") && !find_variable(compressor, "Infinity");
-            && !compressor.find_parent(AST_Scope).find_variable("Infinity");
         return retain ? self : make_node(AST_Binary, self, {
             operator: "/",
             left: make_node(AST_Number, self, {
@@ -3552,7 +3562,7 @@ merge(Compressor.prototype, {
     });
 
     OPT(AST_NaN, function(self, compressor){
-        return compressor.find_parent(AST_Scope).find_variable("NaN") ? make_node(AST_Binary, self, {
+        return find_variable(compressor, "NaN") ? make_node(AST_Binary, self, {
             operator: "/",
             left: make_node(AST_Number, self, {
                 value: 0

test/compress/evaluate.js

@@ -802,3 +802,58 @@ issue_1649: {
     }
     expect_stdout: "-2";
 }
+
+issue_1760_1: {
+    options = {
+        evaluate: true,
+    }
+    input: {
+        !function(a) {
+            try {
+                throw 0;
+            } catch (NaN) {
+                a = +"foo";
+            }
+            console.log(a);
+        }();
+    }
+    expect: {
+        !function(a) {
+            try {
+                throw 0;
+            } catch (NaN) {
+                a = 0 / 0;
+            }
+            console.log(a);
+        }();
+    }
+    expect_stdout: "NaN"
+}
+
+issue_1760_2: {
+    options = {
+        evaluate: true,
+        keep_infinity: true,
+    }
+    input: {
+        !function(a) {
+            try {
+                throw 0;
+            } catch (Infinity) {
+                a = 123456789 / 0;
+            }
+            console.log(a);
+        }();
+    }
+    expect: {
+        !function(a) {
+            try {
+                throw 0;
+            } catch (Infinity) {
+                a = 1 / 0;
+            }
+            console.log(a);
+        }();
+    }
+    expect_stdout: "Infinity"
+}