Define keywords (#13213)

# Description
Some commands in `nu-cmd-lang` are not classified as keywords even
though they should be.

# User-Facing Changes
In the output of `which`, `scope commands`, and `help commands`, some
commands will now have a `type` of `keyword` instead of `built-in`.

crates/nu-parser/src/parse_keywords.rs

@@ -42,32 +42,44 @@ use crate::{
 };
 
 /// These parser keywords can be aliased
-pub const ALIASABLE_PARSER_KEYWORDS: &[&[u8]] = &[b"overlay hide", b"overlay new", b"overlay use"];
+pub const ALIASABLE_PARSER_KEYWORDS: &[&[u8]] = &[
+    b"if",
+    b"match",
+    b"try",
+    b"overlay",
+    b"overlay hide",
+    b"overlay new",
+    b"overlay use",
+];
 
 pub const RESERVED_VARIABLE_NAMES: [&str; 3] = ["in", "nu", "env"];
 
 /// These parser keywords cannot be aliased (either not possible, or support not yet added)
 pub const UNALIASABLE_PARSER_KEYWORDS: &[&[u8]] = &[
-    b"export",
-    b"def",
-    b"export def",
-    b"for",
-    b"extern",
-    b"export extern",
     b"alias",
-    b"export alias",
-    b"export-env",
+    b"const",
+    b"def",
+    b"extern",
     b"module",
     b"use",
+    b"export",
+    b"export alias",
+    b"export const",
+    b"export def",
+    b"export extern",
+    b"export module",
     b"export use",
-    b"hide",
-    // b"overlay",
-    // b"overlay hide",
-    // b"overlay new",
-    // b"overlay use",
+    b"for",
+    b"loop",
+    b"while",
+    b"return",
+    b"break",
+    b"continue",
     b"let",
-    b"const",
     b"mut",
+    b"hide",
+    b"export-env",
+    b"source-env",
     b"source",
     b"where",
     b"register",

crates/nu-parser/src/parser.rs

@@ -934,15 +934,12 @@ pub fn parse_internal_call(
     let output = signature.get_output_type();
 
     // storing the var ID for later due to borrowing issues
-    let lib_dirs_var_id = if decl.is_builtin() {
-        match decl.name() {
-            "use" | "overlay use" | "source-env" | "nu-check" => {
-                find_dirs_var(working_set, LIB_DIRS_VAR)
-            }
-            _ => None,
+    let lib_dirs_var_id = match decl.name() {
+        "use" | "overlay use" | "source-env" if decl.is_keyword() => {
+            find_dirs_var(working_set, LIB_DIRS_VAR)
         }
-    } else {
-        None
+        "nu-check" if decl.is_builtin() => find_dirs_var(working_set, LIB_DIRS_VAR),
+        _ => None,
     };
 
     // The index into the positional parameter in the definition