Breaks some downstream tests that assumed the error message was written a certain way.

core/src/com/google/inject/internal/ChildBindingAlreadySetError.java

@@ -21,10 +21,8 @@ final class ChildBindingAlreadySetError extends InternalErrorDetail<ChildBinding
     super(
         ErrorId.CHILD_BINDING_ALREADY_SET,
         String.format(
-            "A binding for %s already exists in one or more child injectors or private modules."
-                + " Bindings from children can only be used by a parent if the child was a"
-                + " PrivateModule and the binding was exposed. Parent injectors cannot create"
-                + " bindings that already exist in a child.",
+            "Unable to create binding for %s because it was already configured on one or more"
+                + " child injectors or private modules.",
             Messages.convert(key)),
         sources,
         null);

core/test/com/google/inject/JitBindingsTest.java

@@ -53,12 +53,10 @@ private String jitInParentFailed(TypeLiteral<?> clazz) {
   }
 
   private String inChildMessage(Class<?> clazz) {
-    return "A binding for JitBindingsTest$"
+    return "Unable to create binding for "
+        + "JitBindingsTest$"
         + clazz.getSimpleName()
-        + " already exists in one or more child"
-        + " injectors or private modules. Bindings from children can only be used by a parent if"
-        + " the child was a PrivateModule and the binding was exposed. Parent injectors cannot"
-        + " create bindings that already exist in a child.";
+        + " because it was already configured on one or more child injectors or private modules";
   }
 
   public void testLinkedBindingWorks() {

core/test/com/google/inject/ParentInjectorTest.java

@@ -41,9 +41,7 @@
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
-/**
- * @author jessewilson@google.com (Jesse Wilson)
- */
+/** @author jessewilson@google.com (Jesse Wilson) */
 @RunWith(JUnit4.class)
 public class ParentInjectorTest {
 
@@ -72,10 +70,8 @@ public void testParentJitBindingWontClobberChildBinding() {
     } catch (ConfigurationException e) {
       assertContains(
           e.getMessage(),
-          "A binding for ParentInjectorTest$A already exists in one or more child injectors or"
-              + " private modules. Bindings from children can only be used by a parent if the child"
-              + " was a PrivateModule and the binding was exposed. Parent injectors cannot create"
-              + " bindings that already exist in a child.",
+          "Unable to create binding for ParentInjectorTest$A because it was already configured on"
+              + " one or more child injectors or private modules.",
           "ParentInjectorTest$9.configure");
     }
   }

core/test/com/google/inject/PrivateModuleTest.java

@@ -32,9 +32,7 @@
 import java.util.List;
 import junit.framework.TestCase;
 
-/**
- * @author jessewilson@google.com (Jesse Wilson)
- */
+/** @author jessewilson@google.com (Jesse Wilson) */
 public class PrivateModuleTest extends TestCase {
 
   public void testBasicUsage() {
@@ -591,10 +589,8 @@ public void testParentBindsSomethingInPrivate() {
       assertEquals(1, expected.getErrorMessages().size());
       assertContains(
           expected.toString(),
-          "A binding for List<String> already exists in one or more child injectors",
-          " or private modules. Bindings from children can only be used by a parent if the child",
-          " was a PrivateModule and the binding was exposed. Parent injectors cannot create",
-          " bindings that already exist in a child.",
+          "Unable to create binding for List<String> ",
+          "because it was already configured on one or more child injectors or private modules.",
           "1 : PrivateModuleTest$FailingPrivateModule.configure",
           "PrivateModuleTest$FailingModule -> PrivateModuleTest$ManyPrivateModules ->"
               + " PrivateModuleTest$FailingPrivateModule",
@@ -614,10 +610,8 @@ public void testParentBindingToPrivateLinkedJitBinding() {
       assertEquals(1, expected.getErrorMessages().size());
       assertContains(
           expected.toString(),
-          "A binding for List<String> already exists in one or more child injectors",
-          " or private modules. Bindings from children can only be used by a parent if the child",
-          " was a PrivateModule and the binding was exposed. Parent injectors cannot create",
-          " bindings that already exist in a child.",
+          "Unable to create binding for List<String> because it was already configured on one or"
+              + " more child injectors or private modules",
           "1 : PrivateModuleTest$FailingPrivateModule.configure",
           "PrivateModuleTest$ManyPrivateModules -> PrivateModuleTest$FailingPrivateModule",
           "2 : PrivateModuleTest$SecondFailingPrivateModule.configure",
@@ -634,10 +628,8 @@ public void testParentBindingToPrivateJitBinding() {
       assertEquals(1, expected.getErrorMessages().size());
       assertContains(
           expected.toString(),
-          "A binding for PrivateModuleTest$PrivateFoo already exists in one or more child",
-          " injectors or private modules. Bindings from children can only be used by a parent if",
-          " the child was a PrivateModule and the binding was exposed. Parent injectors cannot",
-          " create bindings that already exist in a child.",
+          "Unable to create binding for PrivateModuleTest$PrivateFoo because it was already"
+              + " configured on one or more child injectors or private modules.",
           "as a just-in-time binding");
     }
   }

core/test/com/google/inject/errors/testdata/child_binding_already_set_by_just_in_time_binding.txt

@@ -1,6 +1,6 @@
 Guice configuration errors:
 
-1) [Guice/ChildBindingAlreadySet]: A binding for ChildBindingAlreadySetErrorTest$DependsOnFoo already exists in one or more child injectors or private modules. Bindings from children can only be used by a parent if the child was a PrivateModule and the binding was exposed. Parent injectors cannot create bindings that already exist in a child.
+1) [Guice/ChildBindingAlreadySet]: Unable to create binding for ChildBindingAlreadySetErrorTest$DependsOnFoo because it was already configured on one or more child injectors or private modules.
 
 Bound at:
 1 : ChildBindingAlreadySetErrorTest$ChildModule4.configure(ChildBindingAlreadySetErrorTest.java:105)

core/test/com/google/inject/errors/testdata/child_binding_already_set_error.txt

@@ -1,6 +1,6 @@
 Guice configuration errors:
 
-1) [Guice/ChildBindingAlreadySet]: A binding for ChildBindingAlreadySetErrorTest$Foo already exists in one or more child injectors or private modules. Bindings from children can only be used by a parent if the child was a PrivateModule and the binding was exposed. Parent injectors cannot create bindings that already exist in a child.
+1) [Guice/ChildBindingAlreadySet]: Unable to create binding for ChildBindingAlreadySetErrorTest$Foo because it was already configured on one or more child injectors or private modules.
 
 Bound at:
 1 : ChildBindingAlreadySetErrorTest$ChildModule.configure(ChildBindingAlreadySetErrorTest.java:34)

core/test/com/google/inject/errors/testdata/child_binding_already_set_multiple_times_error.txt

@@ -1,6 +1,6 @@
 Guice configuration errors:
 
-1) [Guice/ChildBindingAlreadySet]: A binding for ChildBindingAlreadySetErrorTest$Foo already exists in one or more child injectors or private modules. Bindings from children can only be used by a parent if the child was a PrivateModule and the binding was exposed. Parent injectors cannot create bindings that already exist in a child.
+1) [Guice/ChildBindingAlreadySet]: Unable to create binding for ChildBindingAlreadySetErrorTest$Foo because it was already configured on one or more child injectors or private modules.
 
 Bound at:
 1 : ChildBindingAlreadySetErrorTest$ChildModule.configure(ChildBindingAlreadySetErrorTest.java:34)

core/test/com/google/inject/errors/testdata/multiple_child_binding_already_set_errors.txt

@@ -1,6 +1,6 @@
 Unable to create injector, see the following errors:
 
-1) [Guice/ChildBindingAlreadySet]: A binding for ChildBindingAlreadySetErrorTest$Foo already exists in one or more child injectors or private modules. Bindings from children can only be used by a parent if the child was a PrivateModule and the binding was exposed. Parent injectors cannot create bindings that already exist in a child.
+1) [Guice/ChildBindingAlreadySet]: Unable to create binding for ChildBindingAlreadySetErrorTest$Foo because it was already configured on one or more child injectors or private modules.
 
 Bound at:
 1 : ChildBindingAlreadySetErrorTest$ChildModule.configure(ChildBindingAlreadySetErrorTest.java:34)