When parsing an invalid parameter expansion (eg. ${} or ${foo@bar}) do not

issue a syntax error immediately but save the information that it is erroneous
for later when the parameter expansion is actually done.  This means eg. "false
&& ${}" will not generate an error which seems to be required by POSIX.
Include the invalid parameter expansion in the error message (sometimes
abbreviated with ... because recovering it would require a lot of code).

PR:		105078
Submitted by:	emaste

bin/sh/expand.c

@@ -763,6 +763,11 @@ evalvar(char *p, int flag)
 			goto record;
 		break;
 
+	case VSERROR:
+		c = p - var - 1;
+		error("${%.*s%s}: Bad substitution", c, var,
+		    (c > 0 && *p != CTLENDVAR) ? "..." : "");
+
 	default:
 		abort();
 	}

bin/sh/parser.c

@@ -1228,12 +1228,17 @@ parsesub: {
 				c = pgetc();
 			}
 		} else {
-			if (! is_special(c))
-badsub:				synerror("Bad substitution");
-			USTPUTC(c, out);
-			c = pgetc();
+			if (! is_special(c)) {
+				subtype = VSERROR;
+				if (c == '}')
+					pungetc();
+				else
+					USTPUTC(c, out);
+			} else {
+				USTPUTC(c, out);
+				c = pgetc();
+			}
 		}
-		STPUTC('=', out);
 		flags = 0;
 		if (subtype == 0) {
 			switch (c) {
@@ -1243,9 +1248,13 @@ badsub:				synerror("Bad substitution");
 				/*FALLTHROUGH*/
 			default:
 				p = strchr(types, c);
-				if (p == NULL)
-					goto badsub;
-				subtype = p - types + VSNORMAL;
+				if (p == NULL) {
+					if (flags == VSNUL)
+						STPUTC(':', out);
+					STPUTC(c, out);
+					subtype = VSERROR;
+				} else
+					subtype = p - types + VSNORMAL;
 				break;
 			case '%':
 			case '#':
@@ -1261,9 +1270,10 @@ badsub:				synerror("Bad substitution");
 					break;
 				}
 			}
-		} else {
+		} else if (subtype != VSERROR) {
 			pungetc();
 		}
+		STPUTC('=', out);
 		if (subtype != VSLENGTH && (dblquote || arinest))
 			flags |= VSQUOTE;
 		*(stackblock() + typeloc) = subtype | flags;

bin/sh/parser.h

@@ -60,6 +60,7 @@
 #define VSTRIMRIGHT	0x8		/* ${var%pattern} */
 #define VSTRIMRIGHTMAX 	0x9		/* ${var%%pattern} */
 #define VSLENGTH	0xa		/* ${#var} */
+#define VSERROR		0xb		/* Syntax error, issue when expanded */
 
 
 /*