Add CaseChangingCharStream for t-sql, downgrade antlr

pmd-tsql/src/main/antlr4/net/sourceforge/pmd/lang/tsql/ast/TSqlLexer.g4

@@ -27,7 +27,7 @@ lexer grammar TSqlLexer;
 
 // Basic keywords (from https://msdn.microsoft.com/en-us/library/ms189822.aspx)
 
-options { caseInsensitive = true; }
+/*options { caseInsensitive = true; }*/
 
 ADD:                                   'ADD';
 ALL:                                   'ALL';
@@ -1215,7 +1215,7 @@ LOCAL_ID:           '@' ([A-Z_$@#0-9] | FullWidthLetter)*;
 TEMP_ID:            '#' ([A-Z_$@#0-9] | FullWidthLetter)*;
 DECIMAL:             DEC_DIGIT+;
 ID:                  ( [A-Z_#] | FullWidthLetter) ( [A-Z_#$@0-9] | FullWidthLetter )*;
-STRING options { caseInsensitive=false; } : 'N'? '\'' (~'\'' | '\'\'')* '\'';
+STRING /*options { caseInsensitive=false; }*/ : 'N'? '\'' (~'\'' | '\'\'')* '\'';
 BINARY:              '0' 'X' HEX_DIGIT*;
 FLOAT:               DEC_DOT_DEC;
 REAL:                (DECIMAL | DEC_DOT_DEC) ('E' [+-]? DEC_DIGIT+);
@@ -1265,7 +1265,7 @@ fragment HEX_DIGIT:    [0-9A-F];
 fragment DEC_DIGIT:    [0-9];
 
 
-fragment FullWidthLetter options { caseInsensitive=false; }
+fragment FullWidthLetter /*options { caseInsensitive=false; }*/
     : '\u00c0'..'\u00d6'
     | '\u00d8'..'\u00f6'
     | '\u00f8'..'\u00ff'

pmd-tsql/src/main/java/net/sourceforge/pmd/lang/tsql/cpd/CaseChangingCharStream.java

@@ -0,0 +1,88 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.tsql.cpd;
+
+// Copied from: https://github.com/antlr/antlr4/blob/4.9.1/doc/resources/CaseChangingCharStream.java
+
+import org.antlr.v4.runtime.CharStream;
+import org.antlr.v4.runtime.misc.Interval;
+
+/**
+ * This class supports case-insensitive lexing by wrapping an existing
+ * {@link CharStream} and forcing the lexer to see either upper or
+ * lowercase characters. Grammar literals should then be either upper or
+ * lower case such as 'BEGIN' or 'begin'. The text of the character
+ * stream is unaffected. Example: input 'BeGiN' would match lexer rule
+ * 'BEGIN' if constructor parameter upper=true but getText() would return
+ * 'BeGiN'.
+ */
+class CaseChangingCharStream implements CharStream {
+
+    final CharStream stream;
+    final boolean upper;
+
+    /**
+     * Constructs a new CaseChangingCharStream wrapping the given {@link CharStream} forcing
+     * all characters to upper case or lower case.
+     * @param stream The stream to wrap.
+     * @param upper If true force each symbol to upper case, otherwise force to lower.
+     */
+    CaseChangingCharStream(CharStream stream, boolean upper) {
+        this.stream = stream;
+        this.upper = upper;
+    }
+
+    @Override
+    public String getText(Interval interval) {
+        return stream.getText(interval);
+    }
+
+    @Override
+    public void consume() {
+        stream.consume();
+    }
+
+    @Override
+    public int LA(int i) {
+        int c = stream.LA(i);
+        if (c <= 0) {
+            return c;
+        }
+        if (upper) {
+            return Character.toUpperCase(c);
+        }
+        return Character.toLowerCase(c);
+    }
+
+    @Override
+    public int mark() {
+        return stream.mark();
+    }
+
+    @Override
+    public void release(int marker) {
+        stream.release(marker);
+    }
+
+    @Override
+    public int index() {
+        return stream.index();
+    }
+
+    @Override
+    public void seek(int index) {
+        stream.seek(index);
+    }
+
+    @Override
+    public int size() {
+        return stream.size();
+    }
+
+    @Override
+    public String getSourceName() {
+        return stream.getSourceName();
+    }
+}

pmd-tsql/src/main/java/net/sourceforge/pmd/lang/tsql/cpd/TSqlTokenizer.java

@@ -16,6 +16,7 @@ public class TSqlTokenizer extends AntlrTokenizer {
     @Override
     protected AntlrTokenManager getLexerForSource(SourceCode sourceCode) {
         CharStream charStream = AntlrTokenizer.getCharStreamFromSourceCode(sourceCode);
+        charStream = new CaseChangingCharStream(charStream, true);
         return new AntlrTokenManager(new TSqlLexer(charStream), sourceCode.getFileName());
     }
 }

pom.xml

@@ -98,7 +98,7 @@
         <pmd.plugin.version>3.20.0</pmd.plugin.version>
         <ant.version>1.10.13</ant.version>
         <javadoc.plugin.version>3.4.1</javadoc.plugin.version>
-        <antlr.version>4.11.1</antlr.version>
+        <antlr.version>4.7.2</antlr.version>
 
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>