Fine. Make LinkedElementFactory.getElementId() more strict.

Now we check for specific kinds of InstanceElement members, and require
that we find the corresponding ID in a library outside the current
cycle.

Add a few tests to trigger corresponding paths.

Change-Id: I0bcd7eb6ad3009e637b849017b4dfeac8308b21f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/443904
Reviewed-by: Johnni Winther <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov

pkg/analyzer/lib/src/fine/manifest_context.dart

@@ -370,15 +370,15 @@ extension LinkedElementFactoryExtension on LinkedElementFactory {
       case MixinElement():
         topLevelItem = manifest.declaredMixins[topLevelName];
       case GetterElement():
-        return manifest.declaredGetters[topLevelName]?.id;
+        return manifest.declaredGetters[topLevelName]!.id;
       case SetterElement():
-        return manifest.declaredSetters[topLevelName]?.id;
+        return manifest.declaredSetters[topLevelName]!.id;
       case TopLevelFunctionElement():
-        return manifest.declaredFunctions[topLevelName]?.id;
+        return manifest.declaredFunctions[topLevelName]!.id;
       case TopLevelVariableElement():
-        return manifest.declaredVariables[topLevelName]?.id;
+        return manifest.declaredVariables[topLevelName]!.id;
       case TypeAliasElement():
-        return manifest.declaredTypeAliases[topLevelName]?.id;
+        return manifest.declaredTypeAliases[topLevelName]!.id;
     }
 
     if (topLevelItem == null) {
@@ -392,17 +392,42 @@ extension LinkedElementFactoryExtension on LinkedElementFactory {
       return topLevelItem.id;
     }
 
-    // TODO(scheglov): When implementation is complete, cast unconditionally.
-    if (topLevelItem is InterfaceItem) {
-      var memberName = memberElement.lookupName!.asLookupName;
-      if (element is ConstructorElement) {
-        return topLevelItem.getConstructorId(memberName);
-      }
-      var methodId = topLevelItem.getInterfaceMethodId(memberName);
-      // TODO(scheglov): When implementation is complete, null assert.
-      return methodId;
+    // If not top-level element, then a member in [InstanceElement].
+    var memberName = memberElement.lookupName!.asLookupName;
+    topLevelItem as InstanceItem;
+
+    switch (element) {
+      case FieldElement():
+        if (topLevelItem.getDeclaredFieldId(memberName) case var result?) {
+          return result;
+        }
+      case GetterElement():
+        if (topLevelItem.getDeclaredGetterId(memberName) case var result?) {
+          return result;
+        }
+      case SetterElement():
+        if (topLevelItem.getDeclaredSetterId(memberName) case var result?) {
+          return result;
+        }
+      case MethodElement():
+        if (topLevelItem.getDeclaredMethodId(memberName) case var result?) {
+          return result;
+        }
+    }
+
+    // If we get here, the top-level container is not [ExtensionElement].
+    // So, it must be [InterfaceElement].
+    topLevelItem as InterfaceItem;
+
+    if (element is ConstructorElement) {
+      return topLevelItem.getConstructorId(memberName)!;
     }
 
-    return null;
+    // In rare cases the member is not declared by the element, but added
+    // to the interface as a result of top-merge.
+    return topLevelItem.getInterfaceMethodId(memberName) ??
+        (throw '[runtimeType: ${element.runtimeType}]'
+            '[topLevelName: $topLevelName]'
+            '[memberName: $memberName]');
   }
 }