[gdb/rust] Fix literal truncation

Make sure we error out on overflow instead of truncating in all cases.

I've used as overflow string: "Integer literal is too large", based
on what I found at
<rust-lang/rust>/src/test/ui/parser/int-literal-too-large-span.rs
but perhaps someone has a better idea.

Tested on x86_64-linux, with a build with --enable-targets=all.

gdb/rust-parse.c

@@ -1024,7 +1024,10 @@ rust_parser::lex_number ()
 	    }
 	}
 
-      value = strtoulst (number.c_str () + offset, NULL, radix);
+      const char *trailer;
+      value = strtoulst (number.c_str () + offset, &trailer, radix);
+      if (*trailer != '\0')
+	error ("Integer literal is too large");
       if (implicit_i32 && value >= ((uint64_t) 1) << 31)
 	type = get_type ("i64");
 

gdb/testsuite/gdb.base/parse_number.exp

@@ -113,8 +113,7 @@ proc parse_number { lang n } {
 	    return [list "i64" $n]
 	} else {
 	    # Overflow.
-	    # Some truncated value, should be re_overflow.
+	    return [list $re_overflow $re_overflow]
-	    return [list i64 $any]
 	}
     } elseif { $lang == "d" } {
 	if { [fits_in_type $n 32 s] } {
@@ -274,6 +273,8 @@ proc test_parse_numbers {arch} {
 	    set re_overflow "Overflow on numeric constant\\."
 	} elseif { $lang == "ada" } {
 	    set re_overflow "Integer literal out of range"
+	} elseif { $lang == "rust" } {
+	    set re_overflow "Integer literal is too large"
 	} else {
 	    set re_overflow "Numeric constant too large\\."
 	}