🐛 Resolves the referenced element before parsing colors (#6768)

Fixes #5436.

| Before | After |
|------|------|
|
![image](https://github.com/flutter/flutter-intellij/assets/15884415/632e3d1c-9bf4-4ff9-9b87-dd79930a5830)
|
![image](https://github.com/flutter/flutter-intellij/assets/15884415/c9188e22-4e93-4bc8-a0ab-756b5aec6f43)
|

## Implementation details

- `Colors` and `CupertinoColors` are hard-coded to determine *colored
element*. The condition has been removed, which means all elements will
be predicated.
- Referenced will be resolved before the element gets parsed by text
directly.
- All the additional checks will be called only if the element type is
`VAR_INIT` (for declarations) or `FUNCTION_BODY` (for getters) to avoid
too much performance regression.

Test case:
```dart
import 'package:flutter/material.dart' hide Colors;

const Color _c1 = Color(0xff000000);
final _c2 = _c1;
Color get _c3 => _c2;

void test() {
  const Color c1 = _c1;
  const Color c2 = Color(0xffffffff);
  const Color c3 = Color.fromARGB(255, 123, 231, 31);
  const Color c4 = Color(0xff923998);
  const Color c5 = c2;
  const Color c6 = TC.c1;
  const Color c7 = TC.c2;
  const Color c8 = TC.c3;
  const Color c9 = Colors.black;
}

class TC {
  static const Color c1 = Color(0xff449978);
  static const Color c2 = Color(0xffdb2f7f);
  static const Color c3 = Color.fromARGB(150, 66, 231, 31);
}

class Colors {
  static const Color white = Color(0xffaa9933);
  static const Color tests = Colors.white;
  static const Color black = Colors.tests;
  static const Color tcC1 = TC.c1;
  final Color tcC2 = TC.c2;
  Color get tcC3 => TC.c3;
}
```

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [ ] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] All existing and new tests are passing.

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Author: AlexV525

flutter-idea/src/io/flutter/editor/FlutterColorProvider.java

@@ -14,10 +14,7 @@
 import com.intellij.psi.impl.source.tree.AstBufferUtil;
 import com.jetbrains.lang.dart.DartLanguage;
 import com.jetbrains.lang.dart.DartTokenTypes;
-import com.jetbrains.lang.dart.psi.DartArgumentList;
-import com.jetbrains.lang.dart.psi.DartArguments;
-import com.jetbrains.lang.dart.psi.DartExpression;
-import com.jetbrains.lang.dart.psi.DartLiteralExpression;
+import com.jetbrains.lang.dart.psi.*;
 import io.flutter.FlutterBundle;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -38,7 +35,6 @@ public Color getColorFrom(@NotNull PsiElement element) {
     if (element.getNode().getElementType() != DartTokenTypes.IDENTIFIER) return null;
 
     final String name = element.getText();
-    if (!(name.equals("Colors") || name.equals("CupertinoColors") || name.equals("Color"))) return null;
 
     final PsiElement refExpr = topmostReferenceExpression(element);
     if (refExpr == null) return null;
@@ -62,6 +58,28 @@ else if (parent.getNode().getElementType() == DartTokenTypes.SIMPLE_TYPE) {
       return parseColorElements(parent, refExpr);
     }
     else {
+      if (parent.getNode().getElementType() == DartTokenTypes.VAR_INIT ||
+          parent.getNode().getElementType() == DartTokenTypes.FUNCTION_BODY) {
+        final PsiElement reference = resolveReferencedElement(refExpr);
+        if (reference != null && reference.getLastChild() != null) {
+          Color tryParseColor = null;
+          if (reference instanceof DartCallExpression) {
+            final DartExpression expression = ((DartCallExpression)reference).getExpression();
+            if (expression != null && expression.getLastChild() instanceof DartReferenceExpression) {
+              tryParseColor = parseColorElements(reference, expression);
+              if (tryParseColor != null) return tryParseColor;
+            }
+          }
+          final PsiElement lastChild = reference.getLastChild();
+          if (lastChild instanceof DartArguments && reference.getParent() != null) {
+            tryParseColor = parseColorElements(reference, reference.getParent());
+          }
+          else {
+            tryParseColor = parseColorElements(reference, reference.getLastChild());
+          }
+          if (tryParseColor != null) return tryParseColor;
+        }
+      }
       // name.equals(refExpr.getFirstChild().getText()) -> Colors.blue
       final PsiElement idNode = refExpr.getFirstChild();
       if (idNode == null) return null;
@@ -82,6 +100,36 @@ else if (parent.getNode().getElementType() == DartTokenTypes.SIMPLE_TYPE) {
     return null;
   }
 
+  @Nullable
+  private PsiElement resolveReferencedElement(@NotNull PsiElement element) {
+    if (element instanceof DartCallExpression && element.getFirstChild().getText().equals("Color")) {
+      return element;
+    }
+    final PsiElement symbol = element.getLastChild();
+    final PsiElement result;
+    if (symbol instanceof DartReference) {
+      result = ((DartReference)symbol).resolve();
+    }
+    else if (element instanceof DartReference) {
+      result = ((DartReference)element).resolve();
+    }
+    else {
+      return null;
+    }
+    if (!(result instanceof DartComponentName) || result.getParent() == null) return null;
+    final PsiElement declaration = result.getParent().getParent();
+    if (!(declaration instanceof DartVarDeclarationList)) return null;
+    final PsiElement lastChild = declaration.getLastChild();
+    if (!(lastChild instanceof DartVarInit)) return null;
+
+    final PsiElement effectiveElement = lastChild.getLastChild();
+    // Recursively determine reference if the initialization is still a `DartReference`.
+    if (effectiveElement instanceof DartReference && !(effectiveElement instanceof DartCallExpression)) {
+      return resolveReferencedElement(effectiveElement);
+    }
+    return effectiveElement;
+  }
+
   @Nullable
   private Color parseColorElements(@NotNull PsiElement parent, @NotNull PsiElement refExpr) {
     final PsiElement selectorNode = refExpr.getLastChild();