refactor: restructure CLI into library crate and add semantic analysis phase

Restructure nxc-cli crate:
- Extract main logic into lib.rs with main_entry() function
- Move nexacore binary to separate bin/nexacore.rs file
- Keep nxc binary in main.rs as thin wrapper

Add semantic analysis to compilation pipeline:
- Implement semantic analyzer with type checking and name resolution
- Add Type enum with Int, Float, Bool, String, Void, Struct, Function, Error variants
- Add typed AST nodes (TypedModule, TypedFunction

crates/nxc-cli/Cargo.toml

@@ -5,14 +5,16 @@ edition.workspace = true
 license.workspace = true
 authors.workspace = true
 
+[lib]
+path = "src/lib.rs"
+
 [[bin]]
 name = "nxc"
 path = "src/main.rs"
 
 [[bin]]
 name = "nexacore"
-path = "src/main.rs"
+path = "src/bin/nexacore.rs"
 
 [dependencies]
 nxc-driver = { path = "../nxc-driver" }
-

crates/nxc-cli/src/bin/nexacore.rs

@@ -0,0 +1,3 @@
+fn main() -> std::process::ExitCode {
+    nxc_cli::main_entry()
+}

crates/nxc-cli/src/lib.rs

@@ -0,0 +1,86 @@
+use std::env;
+use std::path::Path;
+use std::process::ExitCode;
+
+pub fn main_entry() -> ExitCode {
+    match run() {
+        Ok(()) => ExitCode::SUCCESS,
+        Err(message) => {
+            eprintln!("{message}");
+            ExitCode::FAILURE
+        }
+    }
+}
+
+fn run() -> Result<(), String> {
+    let mut args = env::args().skip(1);
+    let Some(command) = args.next() else {
+        print_help();
+        return Ok(());
+    };
+
+    match command.as_str() {
+        "check" | "build" => {
+            let Some(path) = args.next() else {
+                return Err(format!("usage: {} {command} <file.nx>", executable_name()));
+            };
+
+            let output =
+                nxc_driver::check_file(Path::new(&path)).map_err(format_driver_error)?;
+
+            if output.has_errors() {
+                eprintln!("{}", output.render_diagnostics());
+                return Err(format!(
+                    "check failed with {} diagnostic(s)",
+                    output.diagnostics.len()
+                ));
+            }
+
+            let summary = output.summary();
+            println!("checked {}", output.path.display());
+            println!("tokens: {}", output.tokens.len());
+            println!("items: {}", summary.items);
+            println!("functions: {}", summary.functions);
+            println!("structs: {}", summary.structs);
+            Ok(())
+        }
+        "run" => Err("runtime execution is not implemented yet".to_string()),
+        "new" => Err("project scaffolding is not implemented yet".to_string()),
+        "test" => Err("test runner is not implemented yet".to_string()),
+        "fmt" => Err("formatter is not implemented yet".to_string()),
+        "add" => Err("package manager is not implemented yet".to_string()),
+        "doc" => Err("docs generator is not implemented yet".to_string()),
+        _ => Err(format!("unknown command: {command}")),
+    }
+}
+
+fn executable_name() -> String {
+    env::args()
+        .next()
+        .and_then(|path| {
+            Path::new(&path)
+                .file_name()
+                .map(|name| name.to_string_lossy().to_string())
+        })
+        .unwrap_or_else(|| "nxc".to_string())
+}
+
+fn format_driver_error(error: nxc_driver::DriverError) -> String {
+    match error {
+        nxc_driver::DriverError::Io(io) => format!("io error: {io}"),
+    }
+}
+
+fn print_help() {
+    let name = executable_name();
+    println!("NexaCore CLI");
+    println!("usage:");
+    println!("  {name} check <file.nx>");
+    println!("  {name} build <file.nx>");
+    println!("  {name} run <file.nx>");
+    println!("  {name} new <name>");
+    println!("  {name} test");
+    println!("  {name} fmt");
+    println!("  {name} add <package>");
+    println!("  {name} doc");
+}

crates/nxc-cli/src/main.rs

@@ -1,87 +1,4 @@
-use std::env;
-use std::path::Path;
-use std::process::ExitCode;
-
-fn main() -> ExitCode {
-    match run() {
-        Ok(()) => ExitCode::SUCCESS,
-        Err(message) => {
-            eprintln!("{message}");
-            ExitCode::FAILURE
-        }
-    }
-}
-
-fn run() -> Result<(), String> {
-    let mut args = env::args().skip(1);
-    let Some(command) = args.next() else {
-        print_help();
-        return Ok(());
-    };
-
-    match command.as_str() {
-        "check" | "build" => {
-            let Some(path) = args.next() else {
-                return Err(format!("usage: {} {command} <file.nx>", executable_name()));
-            };
-
-            let output =
-                nxc_driver::check_file(Path::new(&path)).map_err(format_driver_error)?;
-
-            if output.has_errors() {
-                eprintln!("{}", output.render_diagnostics());
-                return Err(format!(
-                    "check failed with {} diagnostic(s)",
-                    output.diagnostics.len()
-                ));
-            }
-
-            let summary = output.summary();
-            println!("checked {}", output.path.display());
-            println!("tokens: {}", output.tokens.len());
-            println!("items: {}", summary.items);
-            println!("functions: {}", summary.functions);
-            println!("structs: {}", summary.structs);
-            Ok(())
-        }
-        "run" => Err("runtime execution is not implemented yet".to_string()),
-        "new" => Err("project scaffolding is not implemented yet".to_string()),
-        "test" => Err("test runner is not implemented yet".to_string()),
-        "fmt" => Err("formatter is not implemented yet".to_string()),
-        "add" => Err("package manager is not implemented yet".to_string()),
-        "doc" => Err("docs generator is not implemented yet".to_string()),
-        _ => Err(format!("unknown command: {command}")),
-    }
-}
-
-fn executable_name() -> String {
-    env::args()
-        .next()
-        .and_then(|path| {
-            Path::new(&path)
-                .file_name()
-                .map(|name| name.to_string_lossy().to_string())
-        })
-        .unwrap_or_else(|| "nxc".to_string())
-}
-
-fn format_driver_error(error: nxc_driver::DriverError) -> String {
-    match error {
-        nxc_driver::DriverError::Io(io) => format!("io error: {io}"),
-    }
-}
-
-fn print_help() {
-    let name = executable_name();
-    println!("NexaCore CLI");
-    println!("usage:");
-    println!("  {name} check <file.nx>");
-    println!("  {name} build <file.nx>");
-    println!("  {name} run <file.nx>");
-    println!("  {name} new <name>");
-    println!("  {name} test");
-    println!("  {name} fmt");
-    println!("  {name} add <package>");
-    println!("  {name} doc");
+fn main() -> std::process::ExitCode {
+    nxc_cli::main_entry()
 }
 

crates/nxc-driver/src/lib.rs

@@ -3,7 +3,8 @@ use std::fs;
 use std::path::{Path, PathBuf};
 
 use nxc_frontend::{
-    has_errors, Diagnostic, Item, LexResult, Lexer, Module, ParseResult, Parser, Token,
+    analyze, has_errors, Diagnostic, Item, LexResult, Lexer, Module, ParseResult, Parser, Token,
+    TypedModule,
 };
 
 #[derive(Debug, Clone)]
@@ -12,6 +13,7 @@ pub struct FrontendOutput {
     pub source: String,
     pub tokens: Vec<Token>,
     pub module: Module,
+    pub typed_module: Option<TypedModule>,
     pub diagnostics: Vec<Diagnostic>,
 }
 
@@ -86,13 +88,20 @@ pub fn check_source(path: PathBuf, source: String) -> FrontendOutput {
     } = Parser::new(tokens.clone()).parse_module();
 
     lexer_diagnostics.extend(parser_diagnostics);
+    let mut typed_module = None;
+
+    if !has_errors(&lexer_diagnostics) {
+        let semantic = analyze(&module);
+        lexer_diagnostics.extend(semantic.diagnostics);
+        typed_module = Some(semantic.module);
+    }
 
     FrontendOutput {
         path,
         source,
         tokens,
         module,
+        typed_module,
         diagnostics: lexer_diagnostics,
     }
 }
-

crates/nxc-frontend/src/lib.rs

@@ -2,6 +2,7 @@ pub mod ast;
 pub mod diagnostics;
 pub mod lexer;
 pub mod parser;
+pub mod semantic;
 pub mod token;
 
 pub use ast::{
@@ -11,5 +12,8 @@ pub use ast::{
 pub use diagnostics::{has_errors, Diagnostic, Severity};
 pub use lexer::{LexResult, Lexer};
 pub use parser::{ParseResult, Parser};
+pub use semantic::{
+    analyze, FunctionId, LocalId, SemanticResult, StructId, Type, TypedBlock, TypedExpr,
+    TypedExprKind, TypedFunction, TypedIfStmt, TypedModule, TypedStmt, TypedStmtKind, TypedStruct,
+};
 pub use token::{Keyword, Span, Token, TokenKind};
-

crates/nxc-frontend/tests/semantic_tests.rs

@@ -0,0 +1,223 @@
+use nxc_frontend::{analyze, Lexer, Parser};
+
+fn analyze_source(source: &str) -> nxc_frontend::SemanticResult {
+    let lexed = Lexer::new(source).lex();
+    assert!(
+        lexed.diagnostics.is_empty(),
+        "unexpected lexer diagnostics: {:?}",
+        lexed.diagnostics
+    );
+
+    let parsed = Parser::new(lexed.tokens).parse_module();
+    assert!(
+        parsed.diagnostics.is_empty(),
+        "unexpected parser diagnostics: {:?}",
+        parsed.diagnostics
+    );
+
+    analyze(&parsed.module)
+}
+
+fn messages(result: &nxc_frontend::SemanticResult) -> Vec<String> {
+    result
+        .diagnostics
+        .iter()
+        .map(|diagnostic| diagnostic.message.clone())
+        .collect()
+}
+
+#[test]
+fn rejects_duplicate_function_names() {
+    let result = analyze_source(
+        "\
+fn main() -> Int:
+    return 0
+
+fn main() -> Int:
+    return 1
+",
+    );
+
+    assert!(messages(&result).iter().any(|msg| msg.contains("duplicate function `main`")));
+}
+
+#[test]
+fn rejects_duplicate_parameter_names() {
+    let result = analyze_source(
+        "\
+fn main(value: Int, value: Int) -> Int:
+    return value
+",
+    );
+
+    assert!(messages(&result)
+        .iter()
+        .any(|msg| msg.contains("duplicate parameter `value`")));
+}
+
+#[test]
+fn rejects_duplicate_local_bindings_in_same_scope() {
+    let result = analyze_source(
+        "\
+fn main() -> Int:
+    let value = 1
+    let value = 2
+    return value
+",
+    );
+
+    assert!(messages(&result)
+        .iter()
+        .any(|msg| msg.contains("duplicate binding `value`")));
+}
+
+#[test]
+fn rejects_unknown_identifiers() {
+    let result = analyze_source(
+        "\
+fn main() -> Int:
+    return missing
+",
+    );
+
+    assert!(messages(&result)
+        .iter()
+        .any(|msg| msg.contains("unknown identifier `missing`")));
+}
+
+#[test]
+fn rejects_unknown_function_calls() {
+    let result = analyze_source(
+        "\
+fn main() -> Int:
+    return missing(1)
+",
+    );
+
+    assert!(messages(&result)
+        .iter()
+        .any(|msg| msg.contains("unknown function `missing`")));
+}
+
+#[test]
+fn rejects_invalid_unary_operator_types() {
+    let result = analyze_source(
+        "\
+fn main() -> Int:
+    return -true
+",
+    );
+
+    assert!(messages(&result)
+        .iter()
+        .any(|msg| msg.contains("unary `-` expects `Int` or `Float`")));
+}
+
+#[test]
+fn rejects_invalid_binary_operator_types() {
+    let result = analyze_source(
+        "\
+fn main() -> Int:
+    return true + 1
+",
+    );
+
+    assert!(messages(&result)
+        .iter()
+        .any(|msg| msg.contains("operator `+` expects numeric operands")));
+}
+
+#[test]
+fn rejects_invalid_if_condition_types() {
+    let result = analyze_source(
+        "\
+fn main() -> Int:
+    if 1:
+        return 0
+    else:
+        return 1
+",
+    );
+
+    assert!(messages(&result)
+        .iter()
+        .any(|msg| msg.contains("if condition must be `Bool`")));
+}
+
+#[test]
+fn rejects_wrong_call_arity() {
+    let result = analyze_source(
+        "\
+fn add(a: Int, b: Int) -> Int:
+    return a + b
+
+fn main() -> Int:
+    return add(1)
+",
+    );
+
+    assert!(messages(&result)
+        .iter()
+        .any(|msg| msg.contains("expects 2 argument(s), found 1")));
+}
+
+#[test]
+fn rejects_wrong_call_argument_types() {
+    let result = analyze_source(
+        "\
+fn negate(value: Int) -> Int:
+    return -value
+
+fn main() -> Int:
+    return negate(true)
+",
+    );
+
+    assert!(messages(&result)
+        .iter()
+        .any(|msg| msg.contains("parameter `value` expects `Int`, found `Bool`")));
+}
+
+#[test]
+fn rejects_return_type_mismatch() {
+    let result = analyze_source(
+        "\
+fn main() -> Int:
+    return true
+",
+    );
+
+    assert!(messages(&result)
+        .iter()
+        .any(|msg| msg.contains("return type mismatch: expected `Int`, found `Bool`")));
+}
+
+#[test]
+fn rejects_missing_return_in_non_void_function() {
+    let result = analyze_source(
+        "\
+fn main() -> Int:
+    let value = 1
+",
+    );
+
+    assert!(messages(&result)
+        .iter()
+        .any(|msg| msg.contains("may exit without returning `Int`")));
+}
+
+#[test]
+fn allows_shadowing_in_nested_scopes() {
+    let result = analyze_source(
+        "\
+fn main(value: Int) -> Int:
+    if true:
+        let value = 2
+        return value
+    else:
+        return value
+",
+    );
+
+    assert!(result.diagnostics.is_empty(), "{:?}", result.diagnostics);
+}