prefer variants without leading underscores when case sensitivity=first letter (OC-3547)

java/java-tests/testData/codeInsight/completion/normalSorting/DispreferUnderscoredCaseMismatch.java

@@ -0,0 +1,5 @@
+class Zoo {
+  void zoo(String fooBar, String __FOO_BAR) {
+    foo<caret>
+  }
+}

java/java-tests/testSrc/com/intellij/codeInsight/completion/NormalCompletionOrderingTest.groovy

@@ -460,6 +460,10 @@ interface TxANotAnno {}
     checkPreferredItems(0, 'fooBar', '_fooBar', 'FooBar')
   }
 
+  public void testDispreferUnderscoredCaseMismatch() {
+    checkPreferredItems(0, 'fooBar', '__FOO_BAR')
+  }
+
   public void testStatisticsMattersOnNextCompletion() {
     configureByFile(getTestName(false) + ".java")
     myFixture.completeBasic();

platform/lang-impl/src/com/intellij/codeInsight/completion/impl/CamelHumpMatcher.java

@@ -143,7 +143,7 @@ public class CamelHumpMatcher extends PrefixMatcher {
       int matchStart = ranges.get(0).getStartOffset();
       int underscoreEnd = skipUnderscores(string);
       if (matchStart > 0 && matchStart <= underscoreEnd) {
-        return myMatcher.matchingDegree(string.substring(matchStart)) - 1;
+        return myCaseInsensitiveMatcher.matchingDegree(string.substring(matchStart)) - 1;
       }
     }