Fix some expects, add subcommand alias

crates/nu-parser/src/errors.rs

@@ -1,6 +1,36 @@
+use crate::parser_state::Type;
+use crate::ParserWorkingSet;
 use std::ops::Range;
 
-use crate::ParserWorkingSet;
+pub use crate::Span;
+
+#[derive(Debug)]
+pub enum ParseError {
+    ExtraTokens(Span),
+    ExtraPositional(Span),
+    UnexpectedEof(String, Span),
+    Unclosed(String, Span),
+    UnknownStatement(Span),
+    Expected(String, Span),
+    Mismatch(String, String, Span), // expected, found, span
+    UnsupportedOperation(Span, Span, Type, Span, Type),
+    ExpectedKeyword(String, Span),
+    MultipleRestParams(Span),
+    VariableNotFound(Span),
+    UnknownCommand(Span),
+    NonUtf8(Span),
+    UnknownFlag(Span),
+    UnknownType(Span),
+    MissingFlagParam(Span),
+    ShortFlagBatchCantTakeArg(Span),
+    MissingPositional(String, Span),
+    MissingType(Span),
+    TypeMismatch(Type, Type, Span), // expected, found, span
+    MissingRequiredFlag(String, Span),
+    IncompleteMathExpression(Span),
+    UnknownState(String, Span),
+    IncompleteParser(Span),
+}
 
 impl<'a> codespan_reporting::files::Files<'a> for ParserWorkingSet<'a> {
     type FileId = usize;