fix corner case in templates (#5137)

fixes #5136

lib/compress.js

@@ -11374,15 +11374,6 @@ merge(Compressor.prototype, {
                 if (!tag) status = typeof trimmed;
             }
             if (!tag && strs.length > 1) {
-                if (strs[0] == "") return make_node(AST_Binary, self, {
-                    operator: "+",
-                    left: exprs[0],
-                    right: make_node(AST_Template, self, {
-                        expressions: exprs.slice(1),
-                        strings: strs.slice(1),
-                        tag: tag,
-                    }).transform(compressor),
-                }).optimize(compressor);
                 if (strs[strs.length - 1] == "") return make_node(AST_Binary, self, {
                     operator: "+",
                     left: make_node(AST_Template, self, {
@@ -11392,6 +11383,15 @@ merge(Compressor.prototype, {
                     }).transform(compressor),
                     right: exprs[exprs.length - 1],
                 }).optimize(compressor);
+                if (strs[0] == "") return make_node(AST_Binary, self, {
+                    operator: "+",
+                    left: exprs[0],
+                    right: make_node(AST_Template, self, {
+                        expressions: exprs.slice(1),
+                        strings: strs.slice(1),
+                        tag: tag,
+                    }).transform(compressor),
+                }).optimize(compressor);
             }
             self.expressions = exprs;
             self.strings = strs;

test/compress/templates.js

@@ -685,3 +685,17 @@ issue_5125_8: {
     expect_stdout: "undefinedundefinedundefined PASS"
     node_version: ">=4"
 }
+
+issue_5136: {
+    options = {
+        templates: true,
+    }
+    input: {
+        console.log(`${A = []}${A[0] = 42}`);
+    }
+    expect: {
+        console.log(`` + (A = []) + (A[0] = 42));
+    }
+    expect_stdout: "42"
+    node_version: ">=4"
+}