diff --git a/tool-testsuite/test/org/antlr/v4/test/tool/TestSymbolIssues.java b/tool-testsuite/test/org/antlr/v4/test/tool/TestSymbolIssues.java
index 1c31749a9..e591a986b 100644
--- a/tool-testsuite/test/org/antlr/v4/test/tool/TestSymbolIssues.java
+++ b/tool-testsuite/test/org/antlr/v4/test/tool/TestSymbolIssues.java
@@ -127,7 +127,7 @@ public class TestSymbolIssues extends BaseJavaToolTest {
 		"M1: 'b';\n",
 
 		// YIELDS
-		"error(" + ErrorType.DECLARATION_CONFLICTS_WITH_COMMON_CONSTANTS.code + "): F.g4:3:0: cannot declare mode, token or channel with reserved name M1\n"
+		"error(" + ErrorType.MODE_CONFLICTS_WITH_TOKEN.code + "): F.g4:3:0: mode M1 conflicts with token with same name\n"
 	};
 
 	@Before
@@ -204,9 +204,9 @@ public class TestSymbolIssues extends BaseJavaToolTest {
 			"C: 'c';",
 
 			"error(" + ErrorType.RESERVED_RULE_NAME.code + "): L.g4:5:0: cannot declare a rule with reserved name MIN_CHAR_VALUE\n" +
-			"error(" + ErrorType.DECLARATION_CONFLICTS_WITH_COMMON_CONSTANTS.code + "): L.g4:4:0: cannot declare mode, token or channel with reserved name MAX_CHAR_VALUE\n" +
-			"error(" + ErrorType.DECLARATION_CONFLICTS_WITH_COMMON_CONSTANTS.code + "): L.g4:2:11: cannot declare mode, token or channel with reserved name SKIP\n" +
-			"error(" + ErrorType.DECLARATION_CONFLICTS_WITH_COMMON_CONSTANTS.code + "): L.g4:2:17: cannot declare mode, token or channel with reserved name HIDDEN\n"
+			"error(" + ErrorType.MODE_CONFLICTS_WITH_COMMON_CONSTANTS.code + "): L.g4:4:0: cannot use or declare mode with reserved name MAX_CHAR_VALUE\n" +
+			"error(" + ErrorType.CHANNEL_CONFLICTS_WITH_COMMON_CONSTANTS.code + "): L.g4:2:11: cannot use or declare channel with reserved name SKIP\n" +
+			"error(" + ErrorType.CHANNEL_CONFLICTS_WITH_COMMON_CONSTANTS.code + "): L.g4:2:17: cannot use or declare channel with reserved name HIDDEN\n"
 		};
 
 		testErrors(test, false);
@@ -222,9 +222,9 @@ public class TestSymbolIssues extends BaseJavaToolTest {
 			"E: 'e' -> type(EOF);\n" +
 			"F: 'f' -> pushMode(DEFAULT_MODE);",
 
-			"warning(" + ErrorType.UNKNOWN_OR_WRONG_LEXER_CONSTANT.code + "): L.g4:2:18: rule A contains a lexer command with an unrecognized or wrong constant value; lexer interpreters may produce incorrect output\n" +
-			"warning(" + ErrorType.UNKNOWN_OR_WRONG_LEXER_CONSTANT.code + "): L.g4:3:15: rule B contains a lexer command with an unrecognized or wrong constant value; lexer interpreters may produce incorrect output\n" +
-			"warning(" + ErrorType.UNKNOWN_OR_WRONG_LEXER_CONSTANT.code + "): L.g4:4:15: rule C contains a lexer command with an unrecognized or wrong constant value; lexer interpreters may produce incorrect output\n"
+			"error(" + ErrorType.CHANNEL_CONFLICTS_WITH_COMMON_CONSTANTS.code + "): L.g4:2:18: cannot use or declare channel with reserved name SKIP\n" +
+			"error(" + ErrorType.TOKEN_CONFLICTS_WITH_COMMON_CONSTANTS.code + "): L.g4:3:15: cannot use or declare token with reserved name MORE\n" +
+			"error(" + ErrorType.MODE_CONFLICTS_WITH_COMMON_CONSTANTS.code + "): L.g4:4:15: cannot use or declare mode with reserved name SKIP\n"
 		};
 
 		testErrors(test, false);
@@ -240,9 +240,9 @@ public class TestSymbolIssues extends BaseJavaToolTest {
 			"mode MODE1;\n" +
 			"MODE1_TOKEN: 'qwer';",
 
-			"warning(" + ErrorType.UNKNOWN_OR_WRONG_LEXER_CONSTANT.code + "): L.g4:4:22: rule TOKEN contains a lexer command with an unrecognized or wrong constant value; lexer interpreters may produce incorrect output\n" +
-			"warning(" + ErrorType.UNKNOWN_OR_WRONG_LEXER_CONSTANT.code + "): L.g4:4:41: rule TOKEN contains a lexer command with an unrecognized or wrong constant value; lexer interpreters may produce incorrect output\n" +
-			"warning(" + ErrorType.UNKNOWN_OR_WRONG_LEXER_CONSTANT.code + "): L.g4:4:54: rule TOKEN contains a lexer command with an unrecognized or wrong constant value; lexer interpreters may produce incorrect output\n"
+			"warning(" + ErrorType.UNKNOWN_LEXER_CONSTANT.code + "): L.g4:4:22: rule TOKEN contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output\n" +
+			"warning(" + ErrorType.UNKNOWN_LEXER_CONSTANT.code + "): L.g4:4:41: rule TOKEN contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output\n" +
+			"warning(" + ErrorType.UNKNOWN_LEXER_CONSTANT.code + "): L.g4:4:54: rule TOKEN contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output\n"
 		};
 
 		testErrors(test, false);
diff --git a/tool-testsuite/test/org/antlr/v4/test/tool/TestToolSyntaxErrors.java b/tool-testsuite/test/org/antlr/v4/test/tool/TestToolSyntaxErrors.java
index 3b71460a9..c22d170ac 100644
--- a/tool-testsuite/test/org/antlr/v4/test/tool/TestToolSyntaxErrors.java
+++ b/tool-testsuite/test/org/antlr/v4/test/tool/TestToolSyntaxErrors.java
@@ -657,8 +657,8 @@ public class TestToolSyntaxErrors extends BaseJavaToolTest {
 			"WHITESPACE: [ \\t]+      -> channel(WHITESPACE_CHANNEL);\n";
 
 		String expected =
-			"warning(" + ErrorType.UNKNOWN_OR_WRONG_LEXER_CONSTANT.code + "): T.g4:10:35: rule COMMENT contains a lexer command with an unrecognized or wrong constant value; lexer interpreters may produce incorrect output\n" +
-			"warning(" + ErrorType.UNKNOWN_OR_WRONG_LEXER_CONSTANT.code + "): T.g4:11:35: rule WHITESPACE contains a lexer command with an unrecognized or wrong constant value; lexer interpreters may produce incorrect output\n" +
+			"warning(" + ErrorType.UNKNOWN_LEXER_CONSTANT.code + "): T.g4:10:35: rule COMMENT contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output\n" +
+			"warning(" + ErrorType.UNKNOWN_LEXER_CONSTANT.code + "): T.g4:11:35: rule WHITESPACE contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output\n" +
 			"error(" + ErrorType.CHANNELS_BLOCK_IN_COMBINED_GRAMMAR.code + "): T.g4:3:0: custom channels are not supported in combined grammars\n";
 
 		String[] pair = { grammar, expected };
@@ -686,7 +686,7 @@ public class TestToolSyntaxErrors extends BaseJavaToolTest {
 
 		// WHITESPACE_CHANNEL and COMMENT_CHANNEL are defined, but NEWLINE_CHANNEL is not
 		String expected =
-			"warning(" + ErrorType.UNKNOWN_OR_WRONG_LEXER_CONSTANT.code + "): T.g4:10:34: rule NEWLINE contains a lexer command with an unrecognized or wrong constant value; lexer interpreters may produce incorrect output\n";
+			"warning(" + ErrorType.UNKNOWN_LEXER_CONSTANT.code + "): T.g4:10:34: rule NEWLINE contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output\n";
 
 		String[] pair = { grammar, expected };
 		super.testErrors(pair, true);
diff --git a/tool/src/org/antlr/v4/automata/LexerATNFactory.java b/tool/src/org/antlr/v4/automata/LexerATNFactory.java
index b9fec8abd..979d8d3ab 100644
--- a/tool/src/org/antlr/v4/automata/LexerATNFactory.java
+++ b/tool/src/org/antlr/v4/automata/LexerATNFactory.java
@@ -465,6 +465,10 @@ public class LexerATNFactory extends ParserATNFactory {
 		if (mode >= 0) {
 			return mode;
 		}
+		else if (COMMON_CONSTANTS.containsKey(modeName)) {
+			g.tool.errMgr.grammarError(ErrorType.MODE_CONFLICTS_WITH_COMMON_CONSTANTS, g.fileName, token, token.getText());
+			return null;
+		}
 
 		return tryParseInt(modeName, token);
 	}
@@ -482,6 +486,10 @@ public class LexerATNFactory extends ParserATNFactory {
 		if (tokenType != org.antlr.v4.runtime.Token.INVALID_TYPE) {
 			return tokenType;
 		}
+		else if (COMMON_CONSTANTS.containsKey(tokenName)) {
+			g.tool.errMgr.grammarError(ErrorType.TOKEN_CONFLICTS_WITH_COMMON_CONSTANTS, g.fileName, token, token.getText());
+			return null;
+		}
 
 		return tryParseInt(tokenName, token);
 	}
@@ -494,9 +502,13 @@ public class LexerATNFactory extends ParserATNFactory {
 		if (channelName.equals("HIDDEN")) {
 			return Lexer.HIDDEN;
 		}
-		if (channelName.equals("DEFAULT_TOKEN_CHANNEL")) {
+		else if (channelName.equals("DEFAULT_TOKEN_CHANNEL")) {
 			return Lexer.DEFAULT_TOKEN_CHANNEL;
 		}
+		else if (COMMON_CONSTANTS.containsKey(channelName)) {
+			g.tool.errMgr.grammarError(ErrorType.CHANNEL_CONFLICTS_WITH_COMMON_CONSTANTS, g.fileName, token, token.getText());
+			return null;
+		}
 
 		int channelValue = g.getChannelValue(channelName);
 		if (channelValue >= org.antlr.v4.runtime.Token.MIN_USER_CHANNEL_VALUE) {
@@ -510,7 +522,7 @@ public class LexerATNFactory extends ParserATNFactory {
 		try {
 			return Integer.parseInt(name);
 		} catch (NumberFormatException ex) {
-			g.tool.errMgr.grammarError(ErrorType.UNKNOWN_OR_WRONG_LEXER_CONSTANT, g.fileName, token, currentRule.name, token != null ? token.getText() : null);
+			g.tool.errMgr.grammarError(ErrorType.UNKNOWN_LEXER_CONSTANT, g.fileName, token, currentRule.name, token != null ? token.getText() : null);
 			return null;
 		}
 	}
diff --git a/tool/src/org/antlr/v4/semantics/SemanticPipeline.java b/tool/src/org/antlr/v4/semantics/SemanticPipeline.java
index f818be742..bc11fc811 100644
--- a/tool/src/org/antlr/v4/semantics/SemanticPipeline.java
+++ b/tool/src/org/antlr/v4/semantics/SemanticPipeline.java
@@ -293,7 +293,7 @@ public class SemanticPipeline {
 			}
 
 			if (LexerATNFactory.COMMON_CONSTANTS.containsKey(channelName)) {
-				g.tool.errMgr.grammarError(ErrorType.DECLARATION_CONFLICTS_WITH_COMMON_CONSTANTS, g.fileName, channel.token, channelName);
+				g.tool.errMgr.grammarError(ErrorType.CHANNEL_CONFLICTS_WITH_COMMON_CONSTANTS, g.fileName, channel.token, channelName);
 			}
 
 			if (outermost instanceof LexerGrammar) {
diff --git a/tool/src/org/antlr/v4/semantics/SymbolChecks.java b/tool/src/org/antlr/v4/semantics/SymbolChecks.java
index 0249d5aa7..999d9f0b2 100644
--- a/tool/src/org/antlr/v4/semantics/SymbolChecks.java
+++ b/tool/src/org/antlr/v4/semantics/SymbolChecks.java
@@ -278,12 +278,12 @@ public class SymbolChecks {
 			for (String modeName : lexerGrammar.modes.keySet()) {
 				if (!modeName.equals("DEFAULT_MODE") && reservedNames.contains(modeName)) {
 					Rule rule = lexerGrammar.modes.get(modeName).iterator().next();
-					g.tool.errMgr.grammarError(ErrorType.DECLARATION_CONFLICTS_WITH_COMMON_CONSTANTS, g.fileName, rule.ast.parent.getToken(), modeName);
+					g.tool.errMgr.grammarError(ErrorType.MODE_CONFLICTS_WITH_COMMON_CONSTANTS, g.fileName, rule.ast.parent.getToken(), modeName);
 				}
 
 				if (g.getTokenType(modeName) != Token.INVALID_TYPE) {
 					Rule rule = lexerGrammar.modes.get(modeName).iterator().next();
-					g.tool.errMgr.grammarError(ErrorType.DECLARATION_CONFLICTS_WITH_COMMON_CONSTANTS, g.fileName, rule.ast.parent.getToken(), modeName);
+					g.tool.errMgr.grammarError(ErrorType.MODE_CONFLICTS_WITH_TOKEN, g.fileName, rule.ast.parent.getToken(), modeName);
 				}
 			}
 		}
diff --git a/tool/src/org/antlr/v4/tool/ErrorType.java b/tool/src/org/antlr/v4/tool/ErrorType.java
index 1526a632c..28f78f90f 100644
--- a/tool/src/org/antlr/v4/tool/ErrorType.java
+++ b/tool/src/org/antlr/v4/tool/ErrorType.java
@@ -831,7 +831,7 @@ public enum ErrorType {
 	 *
 	 * @since 4.2
 	 */
-	UNKNOWN_OR_WRONG_LEXER_CONSTANT(155, "rule <arg> contains a lexer command with an unrecognized or wrong constant value; lexer interpreters may produce incorrect output", ErrorSeverity.WARNING),
+	UNKNOWN_LEXER_CONSTANT(155, "rule <arg> contains a lexer command with an unrecognized constant value; lexer interpreters may produce incorrect output", ErrorSeverity.WARNING),
 	/**
 	 * Compiler Error 156.
 	 *
@@ -960,21 +960,57 @@ public enum ErrorType {
 	/**
 	 * Compiler Error 170.
 	 *
-	 * <p>can not declare mode, token or channel with reserved name</p>
+	 * <pre>
+	 * mode M1;
+	 * A1: 'a'; // ok
+	 * mode M2;
+	 * A2: 'a'; // ok
+	 * M1: 'b'; // error 170
+	 * </pre>
 	 *
-	 * <p>Reserved names: HIDDEN, DEFAULT_TOKEN_CHANNEL, DEFAULT_MODE, SKIP, MORE, EOF, MAX_CHAR_VALUE, MIN_CHAR_VALUE.
+	 * <p>mode <em>name</em> conflicts with token with same name</p>
 	 */
-	DECLARATION_CONFLICTS_WITH_COMMON_CONSTANTS(170, "cannot declare mode, token or channel with reserved name <arg>", ErrorSeverity.ERROR),
+	MODE_CONFLICTS_WITH_TOKEN(170, "mode <arg> conflicts with token with same name", ErrorSeverity.ERROR),
 	/**
 	 * Compiler Error 171.
 	 *
-	 * <p>string literals cannot be empty</p>
+	 * <p>can not use or declare token with reserved name</p>
+	 *
+	 * <p>Reserved names: HIDDEN, DEFAULT_TOKEN_CHANNEL, SKIP, MORE, MAX_CHAR_VALUE, MIN_CHAR_VALUE.
+	 *
+	 * <p>Can be used but cannot be declared: EOF</p>
+	 */
+	TOKEN_CONFLICTS_WITH_COMMON_CONSTANTS(171, "cannot use or declare token with reserved name <arg>", ErrorSeverity.ERROR),
+	/**
+	 * Compiler Error 172.
+	 *
+	 * <p>can not use or declare channel with reserved name</p>
+	 *
+	 * <p>Reserved names: DEFAULT_MODE, SKIP, MORE, EOF, MAX_CHAR_VALUE, MIN_CHAR_VALUE.
+	 *
+	 * <p>Can be used but cannot be declared: HIDDEN, DEFAULT_TOKEN_CHANNEL</p>
+	 */
+	CHANNEL_CONFLICTS_WITH_COMMON_CONSTANTS(172, "cannot use or declare channel with reserved name <arg>", ErrorSeverity.ERROR),
+	/**
+	 * Compiler Error 173.
+	 *
+	 * <p>can not use or declare mode with reserved name</p>
+	 *
+	 * <p>Reserved names: HIDDEN, DEFAULT_TOKEN_CHANNEL, SKIP, MORE, MAX_CHAR_VALUE, MIN_CHAR_VALUE.
+	 *
+	 * <p>Can be used and cannot declared: DEFAULT_MODE</p>
+	 */
+	MODE_CONFLICTS_WITH_COMMON_CONSTANTS(173, "cannot use or declare mode with reserved name <arg>", ErrorSeverity.ERROR),
+	/**
+	 * Compiler Error 174.
+	 *
+	 * <p>empty strings not allowed</p>
 	 *
 	 * <pre>A: '''test''';</pre>
 	 * <pre>B: '';</pre>
 	 * <pre>C: 'test' '';</pre>
 	 */
-	EMPTY_STRINGS_NOT_ALLOWED(171, "string literals cannot be empty", ErrorSeverity.ERROR),
+	EMPTY_STRINGS_NOT_ALLOWED(174, "string literals cannot be empty", ErrorSeverity.ERROR),
 
 	/*
 	 * Backward incompatibility errors