fix corner case in unsafe evaluate (#4932)

fixes #4931

lib/compress.js

@@ -10778,7 +10778,8 @@ merge(Compressor.prototype, {
 
     OPT(AST_Template, function(self, compressor) {
         if (!compressor.option("templates")) return self;
-        if (!self.tag || is_raw_tag(compressor, self.tag)) {
+        var tag = self.tag;
+        if (!tag || is_raw_tag(compressor, tag)) {
             var exprs = self.expressions.slice();
             var strs = self.strings.slice();
             var CHANGED = false;
@@ -10786,6 +10787,7 @@ merge(Compressor.prototype, {
                 var node = exprs[i];
                 var ev = node.evaluate(compressor);
                 if (ev === node) continue;
+                if (tag && /\r|\\|`/.test(ev)) continue;
                 ev = ("" + ev).replace(/\r|\\|`/g, function(s) {
                     return "\\" + (s == "\r" ? "r" : s);
                 });
@@ -10794,11 +10796,11 @@ merge(Compressor.prototype, {
                 if (typeof make_node(AST_Template, self, {
                     expressions: [],
                     strings: [ combined ],
-                    tag: self.tag,
+                    tag: tag,
                 }).evaluate(compressor) != typeof make_node(AST_Template, self, {
                     expressions: [ node ],
                     strings: strs.slice(i, i + 2),
-                    tag: self.tag,
+                    tag: tag,
                 }).evaluate(compressor)) continue;
                 exprs.splice(i, 1);
                 strs.splice(i, 2, combined);

test/compress/templates.js

@@ -398,3 +398,24 @@ issue_4676: {
     expect_stdout: "PASS"
     node_version: ">=4"
 }
+
+issue_4931: {
+    options = {
+        evaluate: true,
+        templates: true,
+        unsafe: true,
+    }
+    input: {
+        console.log(String.raw`${typeof A} ${"\r"}`);
+        console.log(String.raw`${"\\"} ${"`"}`);
+    }
+    expect: {
+        console.log(String.raw`${typeof A} ${"\r"}`);
+        console.log("\\ `");
+    }
+    expect_stdout: [
+        "undefined \r",
+        "\\ `",
+    ]
+    node_version: ">=4"
+}