got decent start

runtime/Java/src/org/antlr/v4/runtime/Lexer.java

@@ -188,6 +188,14 @@ public abstract class Lexer extends Recognizer<Integer, LexerATNSimulator>
 		}
 	}
 
+	/** When parsing "x = <expr>;" pattern, we use nextTokenOrRuleToken() not
+	 *  nextToken() so <expr> is converted to RULE token instead of tokenizing.
+	 */
+	public Token nextTokenOrRuleToken() {
+		//if ( '<' id '>' or special pattern ) return RULE token for id
+		return nextToken();
+	}
+
 	/** Instruct the lexer to skip creating a token for current lexer rule
 	 *  and look for another token.  nextToken() knows to keep looking when
 	 *  a lexer rule finishes with token set to SKIP_TOKEN.  Recall that

runtime/Java/src/org/antlr/v4/runtime/tree/ParseTreePatternErrorStrategy.java

@@ -0,0 +1,75 @@
+/*
+ * [The "BSD license"]
+ *  Copyright (c) 2012 Terence Parr
+ *  Copyright (c) 2012 Sam Harwell
+ *  All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions
+ *  are met:
+ *
+ *  1. Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *  3. The name of the author may not be used to endorse or promote products
+ *     derived from this software without specific prior written permission.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.antlr.v4.runtime.tree;
+
+import org.antlr.v4.runtime.DefaultErrorStrategy;
+import org.antlr.v4.runtime.Parser;
+import org.antlr.v4.runtime.RecognitionException;
+import org.antlr.v4.runtime.Token;
+
+/** Alter response to errors in rules so it checks for special RULE tokens
+ *  representing patterns like <expr>.
+
+ catch (RecognitionException re) {
+         _localctx.exception = re;
+ 		 // DO NOTHING IF RULE TOKEN
+         _errHandler.reportError(this, re);
+         _errHandler.recover(this, re);
+ }
+
+ if it's a rule token, it'll cause a mismatch or no viable alt error
+ immediately at start token of rule attempt.
+
+ When parsing "x = <expr>;" pattern, we use nextTokenOrRuleToken() not
+ nextToken() so <expr> is converted to RULE token instead of tokenizing.
+ */
+
+public class ParseTreePatternErrorStrategy extends DefaultErrorStrategy {
+
+	public boolean isRuleToken(Token t) {
+		return t.getType() == 33;
+	}
+
+	@Override
+	public void reportError(Parser recognizer, RecognitionException e) {
+		if ( isRuleToken(e.getOffendingToken()) ) {
+			super.reportError(recognizer, e);
+		}
+	}
+
+	@Override
+	public void recover(Parser recognizer, RecognitionException e) {
+		if ( isRuleToken(e.getOffendingToken()) ) {
+			super.recover(recognizer, e);
+		}
+	}
+}
+

runtime/Java/src/org/antlr/v4/runtime/tree/ParseTreePatternLexer.java

@@ -0,0 +1,57 @@
+/*
+ * [The "BSD license"]
+ *  Copyright (c) 2012 Terence Parr
+ *  Copyright (c) 2012 Sam Harwell
+ *  All rights reserved.
+ *
+ *  Redistribution and use in source and binary forms, with or without
+ *  modification, are permitted provided that the following conditions
+ *  are met:
+ *
+ *  1. Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *  3. The name of the author may not be used to endorse or promote products
+ *     derived from this software without specific prior written permission.
+ *
+ *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.antlr.v4.runtime.tree;
+
+import org.antlr.v4.runtime.Lexer;
+import org.antlr.v4.runtime.Token;
+import org.antlr.v4.runtime.atn.ATN;
+
+public class ParseTreePatternLexer extends Lexer {
+	@Override
+	public ATN getATN() {
+		return null;
+	}
+
+	@Override
+	public String[] getRuleNames() {
+		return new String[0];
+	}
+
+	@Override
+	public String getGrammarFileName() {
+		return null;
+	}
+
+	@Override
+	public Token nextToken() {
+		return super.nextToken();
+	}
+}