Bug 327964 EPartService's hidePart may fail when trying to hide a shared part that's in a shared container
The placeholder retrieval code in the EPartService implementation doesn't go far down deep enough and actually stops at the shared container level. This causes the placeholder of the shared part to not be found.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
.createPerspectiveStack();
		window.getChildren().add(perspectiveStack);
		window.setSelectedElement(perspectiveStack);
		MPerspective perspectiveA = AdvancedFactoryImpl.eINSTANCE
				.createPerspective();
		perspectiveStack.getChildren().add(perspectiveA);
		perspectiveStack.setSelectedElement(perspectiveA);
		MPlaceholder partPlaceholderA1 = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		partPlaceholderA1.setRef(partA);
		partA.setCurSharedRef(partPlaceholderA1);
		perspectiveA.getChildren().add(partPlaceholderA1);
		perspectiveA.setSelectedElement(partPlaceholderA1);
		MPlaceholder partPlaceholderB1 = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		partPlaceholderB1.setRef(partB);
		partB.setCurSharedRef(partPlaceholderB1);
		perspectiveA.getChildren().add(partPlaceholderB1);
		MPerspective perspectiveB = AdvancedFactoryImpl.eINSTANCE
				.createPerspective();
		perspectiveStack.getChildren().add(perspectiveB);
		MPlaceholder partPlaceholderA2 = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		partPlaceholderA2.setRef(partA);
		perspectiveB.getChildren().add(partPlaceholderA2);
		perspectiveB.setSelectedElement(partPlaceholderA2);
		MPlaceholder partPlaceholderB2 = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		partPlaceholderB2.setRef(partB);
		perspectiveB.getChildren().add(partPlaceholderB2);