split clippy into lints, plugin and cargo-clippy

clippy_lints/src/mut_reference.rs

@@ -0,0 +1,77 @@
+use rustc::lint::*;
+use rustc::ty::{TypeAndMut, TypeVariants, MethodCall, TyS};
+use rustc::hir::*;
+use syntax::ptr::P;
+use utils::span_lint;
+
+/// **What it does:** This lint detects giving a mutable reference to a function that only requires an immutable reference.
+///
+/// **Why is this bad?** The immutable reference rules out all other references to the value. Also the code misleads about the intent of the call site.
+///
+/// **Known problems:** None
+///
+/// **Example** `my_vec.push(&mut value)`
+declare_lint! {
+    pub UNNECESSARY_MUT_PASSED,
+    Warn,
+    "an argument is passed as a mutable reference although the function/method only demands an \
+     immutable reference"
+}
+
+
+#[derive(Copy,Clone)]
+pub struct UnnecessaryMutPassed;
+
+impl LintPass for UnnecessaryMutPassed {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(UNNECESSARY_MUT_PASSED)
+    }
+}
+
+impl LateLintPass for UnnecessaryMutPassed {
+    fn check_expr(&mut self, cx: &LateContext, e: &Expr) {
+        let borrowed_table = cx.tcx.tables.borrow();
+        match e.node {
+            ExprCall(ref fn_expr, ref arguments) => {
+                let function_type = borrowed_table.node_types
+                                                  .get(&fn_expr.id)
+                                                  .expect("A function with an unknown type is called. \
+                                                           If this happened, the compiler would have \
+                                                           aborted the compilation long ago");
+                if let ExprPath(_, ref path) = fn_expr.node {
+                    check_arguments(cx, arguments, function_type, &path.to_string());
+                }
+            }
+            ExprMethodCall(ref name, _, ref arguments) => {
+                let method_call = MethodCall::expr(e.id);
+                let method_type = borrowed_table.method_map.get(&method_call).expect("This should never happen.");
+                check_arguments(cx, arguments, method_type.ty, &name.node.as_str())
+            }
+            _ => (),
+        }
+    }
+}
+
+fn check_arguments(cx: &LateContext, arguments: &[P<Expr>], type_definition: &TyS, name: &str) {
+    match type_definition.sty {
+        TypeVariants::TyFnDef(_, _, ref fn_type) |
+        TypeVariants::TyFnPtr(ref fn_type) => {
+            let parameters = &fn_type.sig.skip_binder().inputs;
+            for (argument, parameter) in arguments.iter().zip(parameters.iter()) {
+                match parameter.sty {
+                    TypeVariants::TyRef(_, TypeAndMut { mutbl: MutImmutable, .. }) |
+                    TypeVariants::TyRawPtr(TypeAndMut { mutbl: MutImmutable, .. }) => {
+                        if let ExprAddrOf(MutMutable, _) = argument.node {
+                            span_lint(cx,
+                                      UNNECESSARY_MUT_PASSED,
+                                      argument.span,
+                                      &format!("The function/method \"{}\" doesn't need a mutable reference", name));
+                        }
+                    }
+                    _ => (),
+                }
+            }
+        }
+        _ => (),
+    }
+}