Extend nested placeholders resolution to any CharSequence

See gh-32876

spring-core/src/test/java/org/springframework/core/env/PropertySourcesPropertyResolverTests.java

@@ -34,6 +34,7 @@ import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
 
 /**
  * @author Chris Beams
+ * @author Yanming Zhou
  * @since 3.1
  */
 class PropertySourcesPropertyResolverTests {
@@ -300,6 +301,43 @@ class PropertySourcesPropertyResolverTests {
 			.withMessageContaining("Circular");
 	}
 
+	@Test
+	void resolveNestedPlaceholdersIfValueIsCharSequence() {
+		MutablePropertySources ps = new MutablePropertySources();
+		ps.addFirst(new MockPropertySource()
+				.withProperty("p1", "v1")
+				.withProperty("p2", "v2")
+				.withProperty("p3", new CharSequence() {
+
+					static final String underlying = "${p1}:${p2}";
+
+					@Override
+					public int length() {
+						return underlying.length();
+					}
+
+					@Override
+					public char charAt(int index) {
+						return underlying.charAt(index);
+					}
+
+					@Override
+					public CharSequence subSequence(int start, int end) {
+						return underlying.subSequence(start, end);
+					}
+
+					@Override
+					public String toString() {
+						return underlying;
+					}
+				})
+		);
+		ConfigurablePropertyResolver pr = new PropertySourcesPropertyResolver(ps);
+		assertThat(pr.getProperty("p1")).isEqualTo("v1");
+		assertThat(pr.getProperty("p2")).isEqualTo("v2");
+		assertThat(pr.getProperty("p3")).isEqualTo("v1:v2");
+	}
+
 	@Test
 	void ignoreUnresolvableNestedPlaceholdersIsConfigurable() {
 		MutablePropertySources ps = new MutablePropertySources();