FindFirstMigration: use ifPresent when stream element type is primitive and...

FindFirstMigration: use ifPresent when stream element type is primitive and the final statement is an assignment

This case is possible only if we have no non-final locals updated in the loop, so the assignment updates field or array element.
Using common assignment scenario may not work as primitive optionals lack map/filter operations
Fixes IDEA-200209 "Replace with findFirst" produces incompilable code

java/java-impl/src/com/intellij/codeInspection/streamMigration/FindFirstMigration.java

@@ -42,7 +42,9 @@ class FindFirstMigration extends BaseStreamApiMigration {
       PsiStatement[] statements = tb.getStatements();
       if (statements.length != 2) return null;
       PsiAssignmentExpression assignment = ExpressionUtils.getAssignment(statements[0]);
-      if (assignment == null) {
+      if (assignment == null || tb.getVariable().getType() instanceof PsiPrimitiveType) {
+        // if we found an assignment with primitive stream variable, then we are not assigning to local variable
+        // (see StreamApiMigrationInspection#findMigrationForBreak), thus it could be handled via ifPresent()
         if(!(statements[0] instanceof PsiExpressionStatement)) return null;
         PsiExpression expression = ((PsiExpressionStatement)statements[0]).getExpression();
         return ct.replaceAndRestoreComments(

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/findFirst/afterFindFirstMap.java

+// "Replace with findFirst()" "true"
+
+import java.util.stream.IntStream;
+
+class Lookup {
+  boolean matches(char[] lookup) {}
+}
+
+// IDEA-200209
+class C {
+  private Lookup[] lookbehindFormats;
+  private char[] lookupChars;
+  private Lookup lookbehindFormat;
+
+  {
+      IntStream.range(0, lookbehindFormats.length).filter(i -> lookbehindFormats[i].matches(lookupChars)).findFirst().ifPresent(i -> lookbehindFormat = lookbehindFormats[i]);
+
+  }
+}
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java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/streamApiMigration/findFirst/beforeFindFirstMap.java

+// "Replace with findFirst()" "true"
+
+class Lookup {
+  boolean matches(char[] lookup) {}
+}
+
+// IDEA-200209
+class C {
+  private Lookup[] lookbehindFormats;
+  private char[] lookupChars;
+  private Lookup lookbehindFormat;
+
+  {
+    for (int i = 0; i < lookbehin<caret>dFormats.length; i++) {
+      if (lookbehindFormats[i].matches(lookupChars)) {
+        lookbehindFormat = lookbehindFormats[i];
+        break;
+      }
+    }
+
+  }
+}
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