a minimal example added

.vscode/settings.json

 {
     "cSpell.ignoreWords": [
-        "llvm"
-    ]
+        "intrinsics",
+        "lalrpop",
+        "lalrpop mod",
+        "llvm",
+        "mod"
+    ],
+    "rust-analyzer.inlayHints.enable": true
 }
\ No newline at end of file

Cargo.toml

@@ -8,9 +8,14 @@ build = "build.rs" # LALRPOP preprocessing
 
 [build-dependencies.lalrpop] 
 version = "0.19.0"
+features = ["lexer"]
 
 [dependencies]
 lalrpop-util = "0.19.0"
 regex = "1.3.9"
 
-lalrpop = {version = "0.19.0", features = ["lexer"] }
+# lalrpop = {version = "0.19.0", features = ["lexer"] }
+
+[[bin]]
+name = "minimal"
+path = "src/minimal/main.rs"

src/grammar.lalrpop

+use std::str::FromStr;
+
+grammar;
+
+pub Id: String = {
+    r"([a-z]|[A-Z])([a-z]|[A-Z]|[0-9]|_)*" => String::from_str(<>).unwrap(),
+};

src/main.rs

+use lalrpop_util::lalrpop_mod;
+
+lalrpop_mod!(pub grammar);
+
+use grammar::*;
+
+fn main() {
+    println!("hello world");
+}
+
+#[test] 
+fn hello() {
+    println!("Hello in test")
+}
+

src/minimal/main.rs

+use lalrpop_util::lalrpop_mod;
+
+lalrpop_mod!(pub parser, "/minimal/parser.rs");
+
+use parser::*;
+
+fn main() {}
+
+#[test]
+fn parse_id() {
+    println!(
+        "{:?}",
+        IdParser::new().parse(
+            "
+
+            //a1_a //
+
+            /* 
+            a1_a
+            */
+            a1_a
+            "
+        )
+    );
+}
+
+#[test]
+fn parse_num() {
+    println!("{:?}", NumParser::new().parse("123"));
+}
+
+#[test]
+fn parse_num_or_id() {
+    println!("{:?}", NumOrIdParser::new().parse("123"));
+    println!("{:?}", NumOrIdParser::new().parse("a1_a"));
+}

src/minimal/parser.lalrpop

+use std::str::FromStr;
+
+grammar;
+
+match {
+    // The default whitespace skipping is disabled an `ignore pattern` is specified
+    r"\s*" => { }, 
+    // Skip `// comments`
+    r"//[^\n\r]*" => { }, 
+    // Skip `/* comments */`
+    r"/\*([^\*]*\*+[^\*/])*([^\*]*\*+|[^\*])*\*/" => { },  
+    _
+}
+
+pub NumOrId = {
+    Num => <>.to_string(),
+    Id,
+}
+
+pub Num: usize = {
+    r"[0-9]+" => usize::from_str(<>).unwrap(),
+};
+
+pub Id: String = {
+    r"([a-z]|[A-Z])([a-z]|[A-Z]|[0-9]|_)*" => String::from_str(<>).unwrap(),
+};
+
+// lets try to break down the multi-line comment
+//  
+//  should allow patterns like
+//  /*
+//  ...
+//  */
+//  and
+//  /* /*
+//  */
+//  */
+//  but reject patterns like
+//  /* /*
+//  */
+//  and
+//  /* */ */
+//  
+//  Rather tricky right...
+//  
+//  /\*([^\*]*\*+[^\*/])*([^\*]*\*+|[^\*])*\*/
+//  the outer  "/\* ... \*/" requires start and end "/*" ... "*/"
+//  so let's look closer at "([^\*]*\*+[^\*/])*([^\*]*\*+|[^\*])*"
+//  the trailing "*", just means any number of 
+//  "[^\*]*\*+[^\*/])*([^\*]*\*+|[^\*]"
+//
+//  "[^\*]*\*+[^\*/])*"
+//  "[^\*]*"" any number or Not("*"), e.g. 0123
+//  "\*" one or many "*", e.g. *, or ****
+//  .... ehhh I gave up, regexp is haaaaaaarrrrrrrd, another day perhaps
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