Fix summary resynthesis for operators ending in '='.

pkg/analyzer/lib/src/summary/resynthesize.dart

Index: pkg/analyzer/lib/src/summary/resynthesize.dart
diff --git a/pkg/analyzer/lib/src/summary/resynthesize.dart b/pkg/analyzer/lib/src/summary/resynthesize.dart
index 7dfcbeea1384515363ccf50a2704c7137d7dc995..45fd9b17024efbfd699999b616390d98fa9be62d 100644
--- a/pkg/analyzer/lib/src/summary/resynthesize.dart
+++ b/pkg/analyzer/lib/src/summary/resynthesize.dart
@@ -385,11 +385,12 @@ class _LibraryResynthesizer {
     if (holder == null) {
       holder = unitHolder;
     }
+    UnlinkedExecutableKind kind = serializedExecutable.kind;
     String name = serializedExecutable.name;
-    if (name.endsWith('=') && name != '[]=') {
+    if (kind == UnlinkedExecutableKind.setter) {
+      assert(name.endsWith('='));
       name = name.substring(0, name.length - 1);
     }
-    UnlinkedExecutableKind kind = serializedExecutable.kind;
     switch (kind) {
       case UnlinkedExecutableKind.functionOrMethod:
         if (isTopLevel) {