Bug [cb03e57a] - raise error on empty regexp if variable not resolvable

Author: apnadkarni

generic/tclCompCmdsGR.c

@@ -2007,14 +2007,11 @@ TclCompileRegexpCmd(
 	    return TCL_ERROR;
 	}
 
-	if (len == 0) {
-	    /*
-	     * The semantics of regexp are always match on re == "".
-	     */
-
-	    PushStringLiteral(envPtr, "1");
-	    return TCL_OK;
-	}
+	/*
+	 * Note: do not optimize for len == 0, as error should be generated
+	 * at runtime if operand is not a resolvable variable.
+	 * Bug https://core.tcl-lang.org/tcl/info/cb03e57a7b24d22c
+	 */
 
 	/*
 	 * Attempt to convert pattern to glob.  If successful, push the

tests/regexp.test

@@ -1199,6 +1199,11 @@ test regexp-27.12 {regsub -command representation smash} {
     set s {list (.+)}
     regsub -command $s {list list} $s
 } {(.+) {list list} list}
+
+test regexp-28.1 {bug cb03e57a7b} -returnCodes error -body {
+	regexp {} $nosuchvar
+} -result {can't read "nosuchvar": no such variable}
+
 
 # cleanup
 ::tcltest::cleanupTests