Exceptions: Make better exception types

src/fsh.nim

@@ -25,6 +25,17 @@ let builtins: array[4, string] = [
 "exit",
 ]
 
+# Exception types
+type
+  ShellError= object of CatchableError
+    line: int
+    col: int
+    whileExec: string
+  ShellVariableError=object of ShellError
+    variable: string
+  ShellCommandError = object of ShellError
+    command: string
+
 # forward declarations
 proc eval(cmd: string): string
 proc substitute(strm: Stream, delim = ";\p"): string