Closes #290: Support detection of mixed modes in preproc.

Make a more friendly error message when the user is mixing modes, allowing for localization of error.

java/src/processing/mode/java/preproc/PdeParseTreeListener.java

@@ -316,6 +316,23 @@ public class PdeParseTreeListener extends ProcessingBaseListener {
     footerResult = prepareFooter(rewriter, length);
   }
 
+  @Override
+  public void enterWarnMixedModes(ProcessingParser.WarnMixedModesContext ctx) {
+    pdeParseTreeErrorListenerMaybe.ifPresent((listener) -> {
+      Token token = ctx.getStart();
+      int line = token.getLine();
+      int charOffset = token.getCharPositionInLine();
+
+      listener.onError(new PdePreprocessIssue(
+        line,
+        charOffset,
+        PreprocessIssueMessageSimplifier.getLocalStr(
+            "editor.status.bad.mixed_mode"
+        )
+      ));
+    });
+  }
+
   /**
    * Endpoint for ANTLR to call when finished parsing a method invocatino.
    *
@@ -770,7 +787,7 @@ public class PdeParseTreeListener extends ProcessingBaseListener {
    * @return True if setup and false otherwise.
    */
   protected boolean isMethodSetup(ParserRuleContext declaration) {
-    if (declaration.getChildCount() < 2) {
+    if (declaration == null || declaration.getChildCount() < 2) {
       return false;
     }
     return declaration.getChild(1).getText().equals("setup");

java/src/processing/mode/java/preproc/Processing.g4

@@ -23,6 +23,7 @@ processingSketch
     :   javaProcessingSketch
     |   staticProcessingSketch
     |   activeProcessingSketch
+		|   warnMixedModes
     ;
 
 // java mode, is a compilation unit
@@ -30,20 +31,26 @@ javaProcessingSketch
     :   packageDeclaration? importDeclaration* typeDeclaration+ EOF
     ;
 
+// No method declarations, just statements
 staticProcessingSketch
     :   (importDeclaration | blockStatement)* EOF
     ;
 
 // active mode, has function definitions
 activeProcessingSketch
-	:	(importDeclaration | classBodyDeclaration)* EOF
-	;
+	  :	  (importDeclaration | classBodyDeclaration)* EOF
+	  ;
 
 variableDeclaratorId
     :   warnTypeAsVariableName
     |   IDENTIFIER ('[' ']')*
     ;
 
+warnMixedModes
+    :   (importDeclaration | classBodyDeclaration | blockStatement)* blockStatement classBodyDeclaration (importDeclaration | classBodyDeclaration | blockStatement)*
+		|   (importDeclaration | classBodyDeclaration | blockStatement)* classBodyDeclaration blockStatement (importDeclaration | classBodyDeclaration | blockStatement)*
+		;
+
 // bug #93
 // https://github.com/processing/processing/issues/93
 // prevent from types being used as variable names

java/test/processing/mode/java/ParserTests.java

@@ -405,4 +405,9 @@ public class ParserTests {
     expectGood("sizethis");
   }
 
+  @Test
+  public void testMixing() {
+    expectRunnerException("mixing", 1);
+  }
+
 }