feat: add Linter

Cargo.toml

@@ -15,6 +15,7 @@ homepage.workspace = true
 members = [
     "crates/erg_common",
     "crates/erg_compiler",
+    "crates/erg_linter/",
     "crates/erg_parser",
     "crates/els",
     "crates/erg_proc_macros/",
@@ -30,45 +31,50 @@ homepage = "https://erg-lang.org/"
 
 [features]
 # when "debug" feature is turned on, that of the following crates will also be turned on.
-debug = ["erg_common/debug", "erg_parser/debug", "erg_compiler/debug"] # "els/debug"
+debug = ["erg_common/debug", "erg_parser/debug", "erg_compiler/debug", "erg_linter/debug"] # "els/debug"
 backtrace = ["erg_common/backtrace", "els/backtrace"]
 japanese = [
     "erg_common/japanese",
     "erg_parser/japanese",
     "erg_compiler/japanese",
     "els/japanese",
+    "erg_linter/japanese",
 ]
 simplified_chinese = [
     "erg_common/simplified_chinese",
     "erg_parser/simplified_chinese",
     "erg_compiler/simplified_chinese",
     "els/simplified_chinese",
+    "erg_linter/simplified_chinese",
 ]
 traditional_chinese = [
     "erg_common/traditional_chinese",
     "erg_parser/traditional_chinese",
     "erg_compiler/traditional_chinese",
     "els/traditional_chinese",
+    "erg_linter/traditional_chinese",
 ]
-unicode = ["erg_common/unicode", "erg_parser/unicode", "erg_compiler/unicode", "els/unicode"]
-pretty = ["erg_common/pretty", "erg_parser/pretty", "erg_compiler/pretty", "els/pretty"]
+unicode = ["erg_common/unicode", "erg_parser/unicode", "erg_compiler/unicode", "els/unicode", "erg_linter/unicode"]
+pretty = ["erg_common/pretty", "erg_parser/pretty", "erg_compiler/pretty", "els/pretty", "erg_linter/pretty"]
 large_thread = [
     "erg_common/large_thread",
     "erg_parser/large_thread",
     "erg_compiler/large_thread",
     "els/large_thread",
+    "erg_linter/large_thread",
 ]
 py_compat = ["erg_compiler/py_compat", "els/py_compat"]
 gal = ["erg_common/gal", "erg_compiler/gal"]
 els = ["erg_common/els", "erg_compiler/els", "dep:els"]
 full-repl = ["erg_common/full-repl"]
 full = ["els", "full-repl", "unicode", "pretty"]
-experimental = ["erg_common/experimental", "erg_parser/experimental", "erg_compiler/experimental"]
+experimental = ["erg_common/experimental", "erg_parser/experimental", "erg_compiler/experimental", "erg_linter/experimental"]
 
 [workspace.dependencies]
 erg_common = { version = "0.6.33", path = "./crates/erg_common" }
 erg_parser = { version = "0.6.33", path = "./crates/erg_parser" }
 erg_compiler = { version = "0.6.33", path = "./crates/erg_compiler" }
+erg_linter = { version = "0.6.33", path = "./crates/erg_linter" }
 els = { version = "0.1.45", path = "./crates/els" }
 erg_proc_macros = { version = "0.6.33", path = "./crates/erg_proc_macros" }
 pyo3 = { version = "0.20", features = ["extension-module"] }
@@ -77,6 +83,7 @@ pyo3 = { version = "0.20", features = ["extension-module"] }
 erg_common = { workspace = true }
 erg_parser = { workspace = true }
 erg_compiler = { workspace = true }
+erg_linter = { workspace = true }
 els = { workspace = true, optional = true }
 
 [build-dependencies]

crates/els/diagnostics.rs

@@ -11,7 +11,6 @@ use erg_common::dict::Dict;
 use erg_common::pathutil::{project_entry_file_of, project_root_dir_of};
 use erg_common::spawn::{safe_yield, spawn_new_thread};
 use erg_common::style::*;
-use erg_common::traits::Stream;
 use erg_common::{fn_name, lsp_log};
 use erg_compiler::artifact::BuildRunnable;
 use erg_compiler::build_package::CheckStatus;

crates/erg_common/config.rs

@@ -31,6 +31,7 @@ pub enum ErgMode {
     Transpile,
     Execute,
     LanguageServer,
+    Lint,
     Read,
     Pack,
 }
@@ -48,6 +49,7 @@ impl TryFrom<&str> for ErgMode {
             "trans" | "transpile" | "transpiler" => Ok(Self::Transpile),
             "run" | "execute" => Ok(Self::Execute),
             "server" | "language-server" => Ok(Self::LanguageServer),
+            "lint" | "linter" => Ok(Self::Lint),
             "byteread" | "read" | "reader" | "dis" => Ok(Self::Read),
             "pack" | "package" => Ok(Self::Pack),
             _ => Err(()),
@@ -67,6 +69,7 @@ impl From<ErgMode> for &str {
             ErgMode::Transpile => "transpile",
             ErgMode::Execute => "execute",
             ErgMode::LanguageServer => "language-server",
+            ErgMode::Lint => "lint",
             ErgMode::Read => "read",
             ErgMode::Pack => "pack",
         }

crates/erg_compiler/error/mod.rs

@@ -646,6 +646,14 @@ impl CompileErrors {
     pub fn take(&mut self) -> Self {
         self.flush()
     }
+
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
 }
 
 pub type SingleCompileResult<T> = Result<T, CompileError>;

crates/erg_linter/Cargo.toml

@@ -0,0 +1,49 @@
+[package]
+name = "erg_linter"
+description = "the Erg linter"
+documentation = "http://docs.rs/erg_linter"
+version.workspace = true
+authors.workspace = true
+license.workspace = true
+edition.workspace = true
+repository.workspace = true
+homepage.workspace = true
+
+[features]
+debug = ["erg_common/debug", "erg_parser/debug", "erg_compiler/debug"]
+backtrace = ["erg_common/backtrace"]
+japanese = [
+    "erg_common/japanese",
+    "erg_parser/japanese",
+    "erg_compiler/japanese",
+]
+simplified_chinese = [
+    "erg_common/simplified_chinese",
+    "erg_parser/simplified_chinese",
+    "erg_compiler/simplified_chinese",
+]
+traditional_chinese = [
+    "erg_common/traditional_chinese",
+    "erg_parser/traditional_chinese",
+    "erg_compiler/traditional_chinese",
+]
+unicode = ["erg_common/unicode", "erg_parser/unicode", "erg_compiler/unicode"]
+pretty = ["erg_common/pretty", "erg_parser/pretty", "erg_compiler/pretty"]
+large_thread = [
+    "erg_common/large_thread",
+    "erg_parser/large_thread",
+    "erg_compiler/large_thread",
+]
+py_compat = ["erg_compiler/py_compat"]
+gal = ["erg_common/gal", "erg_compiler/gal"]
+full-repl = ["erg_common/full-repl"]
+full = ["full-repl", "unicode", "pretty"]
+experimental = ["erg_common/experimental", "erg_parser/experimental", "erg_compiler/experimental"]
+
+[dependencies]
+erg_common = { workspace = true }
+erg_parser = { workspace = true }
+erg_compiler ={ workspace = true }
+
+[lib]
+path = "lib.rs"

crates/erg_linter/README.md

@@ -8,12 +8,16 @@ The following codes are warned.
 
 * Unreachable codes
 * Wildcard import
-* Unused variables
 * Shadowing of built-in variables
-* Unused objects that are not `NoneLike`
 * Procedures without side-effects
 * Variables that can be defined as constants
 * Unnecessary `.clone`
 * Mutable objects that do not change
 * Hardcoded well-known constants (e.g. `3.14`)
 * Defining a subroutine with too many parameters
+* Defining a class with too many fields
+
+### These are warned by the compiler
+
+* Unused variables
+* Unused objects that are not `NoneLike`

crates/erg_linter/mod.rs → crates/erg_linter/lib.rs

@@ -1,3 +1,4 @@
 mod lint;
+mod warn;
 
 pub use lint::Linter;