rust-lang#333 Catches calls to main() unless #![no_std] attr set (2nd commit: the remaining changes)

Author: thomanski

README.md

@@ -6,13 +6,14 @@ A collection of lints to catch common mistakes and improve your Rust code.
 [Jump to usage instructions](#usage)
 
 ##Lints
-There are 58 lints included in this crate:
+There are 59 lints included in this crate:
 
 name                                                                                                   | default | meaning
 -------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 [approx_constant](https://github.com/Manishearth/rust-clippy/wiki#approx_constant)                     | warn    | the approximate of a known float constant (in `std::f64::consts` or `std::f32::consts`) is found; suggests to use the constant
 [bad_bit_mask](https://github.com/Manishearth/rust-clippy/wiki#bad_bit_mask)                           | warn    | expressions of the form `_ & mask == select` that will only ever return `true` or `false` (because in the example `select` containing bits that `mask` doesn't have)
 [box_vec](https://github.com/Manishearth/rust-clippy/wiki#box_vec)                                     | warn    | usage of `Box<Vec<T>>`, vector elements are already on the heap
+[calling_main](https://github.com/Manishearth/rust-clippy/wiki#calling_main)                           | warn    | calling into main detected
 [cast_possible_truncation](https://github.com/Manishearth/rust-clippy/wiki#cast_possible_truncation)   | allow   | casts that may cause truncation of the value, e.g `x as u8` where `x: u32`, or `x as i32` where `x: f32`
 [cast_possible_wrap](https://github.com/Manishearth/rust-clippy/wiki#cast_possible_wrap)               | allow   | casts that may cause wrapping around the value, e.g `x as i32` where `x: u32` and `x > i32::MAX`
 [cast_precision_loss](https://github.com/Manishearth/rust-clippy/wiki#cast_precision_loss)             | allow   | casts that cause loss of precision, e.g `x as f32` where `x: u64`

src/lib.rs

@@ -127,6 +127,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
         loops::WHILE_LET_LOOP,
         matches::MATCH_REF_PATS,
         matches::SINGLE_MATCH,
+        methods::CALLING_MAIN,
         methods::SHOULD_IMPLEMENT_TRAIT,
         methods::STR_TO_STRING,
         methods::STRING_TO_STRING,

src/methods.rs

@@ -1,9 +1,12 @@
+extern crate syntax;
+
 use rustc_front::hir::*;
 use rustc::lint::*;
 use rustc::middle::ty;
 use rustc::middle::subst::Subst;
 use std::iter;
 use std::borrow::Cow;
+use syntax::ast::{Attribute, MetaWord};
 
 use utils::{snippet, span_lint, match_path, match_type, walk_ptrs_ty_depth};
 use utils::{OPTION_PATH, RESULT_PATH, STRING_PATH};
@@ -30,16 +33,37 @@ declare_lint!(pub WRONG_SELF_CONVENTION, Warn,
 declare_lint!(pub WRONG_PUB_SELF_CONVENTION, Allow,
               "defining a public method named with an established prefix (like \"into_\") that takes \
                `self` with the wrong convention");
+declare_lint!(pub CALLING_MAIN, Warn,
+              "calling into main detected");
 
 impl LintPass for MethodsPass {
     fn get_lints(&self) -> LintArray {
         lint_array!(OPTION_UNWRAP_USED, RESULT_UNWRAP_USED, STR_TO_STRING, STRING_TO_STRING,
-                    SHOULD_IMPLEMENT_TRAIT, WRONG_SELF_CONVENTION)
+                    SHOULD_IMPLEMENT_TRAIT, WRONG_SELF_CONVENTION, CALLING_MAIN)
     }
 }
 
 impl LateLintPass for MethodsPass {
     fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
+        fn no_std_present(cx: &LateContext) -> bool {
+        	let attrs : &[Attribute] = &cx.krate.attrs; // TODO replace these two...
+        	for attr in attrs { // lines with ...
+        	// for &attr in cx.krate.attrs { ... once type inf on nightly fixed
+                if let MetaWord(ref mword) = attr.node.value.node {
+                    if mword == &"no_std" { return true; }
+                }
+            }
+            false
+        }
+        if let ExprCall(ref func, ref args) = expr.node {
+            if args.is_empty() {
+                if let ExprPath(_, path) = func.node.clone() {
+                    if !path.global && path.segments[0].identifier.name.as_str() == "main" && !no_std_present(cx) {
+                        span_lint(cx, CALLING_MAIN, expr.span, "calling into main() detected");
+                    }
+                }
+            }
+        }
         if let ExprMethodCall(ref name, _, ref args) = expr.node {
             let (obj_ty, ptr_depth) = walk_ptrs_ty_depth(cx.tcx.expr_ty(&args[0]));
             if name.node.as_str() == "unwrap" {