From ceb9a8bdd79e4c2081d88d40d3a8a2b6f080268f Mon Sep 17 00:00:00 2001
From: llogiq <bogusandre@gmail.com>
Date: Sun, 7 Feb 2016 22:50:54 +0100
Subject: [PATCH] regex macro lint

---
 src/regex.rs                | 56 +++++++++++++++++++++++++++++++++++--
 tests/compile-fail/regex.rs | 11 ++++++--
 2 files changed, 63 insertions(+), 4 deletions(-)

diff --git a/src/regex.rs b/src/regex.rs
index cf19c764361..e7abc9be876 100644
--- a/src/regex.rs
+++ b/src/regex.rs
@@ -1,14 +1,16 @@
 use regex_syntax;
 use std::error::Error;
 use syntax::ast::Lit_::LitStr;
+use syntax::ast::NodeId;
 use syntax::codemap::{Span, BytePos};
 use syntax::parse::token::InternedString;
 use rustc_front::hir::*;
+use rustc_front::intravisit::{Visitor, walk_block, FnKind};
 use rustc::middle::const_eval::{eval_const_expr_partial, ConstVal};
 use rustc::middle::const_eval::EvalHint::ExprTypeChecked;
 use rustc::lint::*;
 
-use utils::{match_path, REGEX_NEW_PATH, span_lint, span_help_and_lint};
+use utils::{is_expn_of, match_path, REGEX_NEW_PATH, span_lint, span_help_and_lint};
 
 /// **What it does:** This lint checks `Regex::new(_)` invocations for correct regex syntax.
 ///
@@ -37,16 +39,41 @@ declare_lint! {
     "finds trivial regular expressions in `Regex::new(_)` invocations"
 }
 
+/// **What it does:** This lint checks for usage of `regex!(_)` which as of now is usually slower than `Regex::new(_)` unless called in a loop (which is a bad idea anyway).
+///
+/// **Why is this bad?** Performance, at least for now. The macro version is likely to catch up long-term, but for now the dynamic version is faster.
+///
+/// **Known problems:** None
+///
+/// **Example:** `regex!("foo|bar")`
+declare_lint! {
+    pub REGEX_MACRO,
+    Allow,
+    "finds use of `regex!(_)`, suggests `Regex::new(_)` instead"
+}
+
 #[derive(Copy,Clone)]
 pub struct RegexPass;
 
 impl LintPass for RegexPass {
     fn get_lints(&self) -> LintArray {
-        lint_array!(INVALID_REGEX, TRIVIAL_REGEX)
+        lint_array!(INVALID_REGEX, REGEX_MACRO, TRIVIAL_REGEX)
     }
 }
 
 impl LateLintPass for RegexPass {
+    fn check_fn(&mut self, 
+                cx: &LateContext, 
+                _: FnKind, 
+                _: &FnDecl, 
+                block: &Block, 
+                _: Span, 
+                _: NodeId) {
+        let mut visitor = RegexVisitor { cx: cx, last: BytePos(0) };
+        visitor.visit_block(block);
+    }
+
+
     fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
         if_let_chain!{[
             let ExprCall(ref fun, ref args) = expr.node,
@@ -139,3 +166,28 @@ fn is_trivial_regex(s: &regex_syntax::Expr) -> Option<&'static str> {
         _ => None,
     }
 }
+
+struct RegexVisitor<'v, 't: 'v> {
+    cx: &'v LateContext<'v, 't>,
+    last: BytePos
+}
+
+impl<'v, 't: 'v> Visitor<'v> for RegexVisitor<'v, 't> {
+    fn visit_block(&mut self, block: &'v Block) {
+        if let Some(ref expr) = block.expr {
+            if let Some(span) = is_expn_of(self.cx, expr.span, "regex") {
+                if span.lo == BytePos(0) || span.lo == self.last {
+                    return;
+                }
+                span_lint(self.cx, 
+                          REGEX_MACRO, 
+                          span,
+                          &format!("regex!(_): {:?}, {:?}", self.last, span.lo));
+                          //"`regex!(_)` found. Use `Regex::new(_)`, which is faster for now.");
+                self.last = span.lo;
+                return;
+            }
+        }
+        walk_block(self, block);
+    }
+}
diff --git a/tests/compile-fail/regex.rs b/tests/compile-fail/regex.rs
index 2e8228a823d..df52cc3dff0 100644
--- a/tests/compile-fail/regex.rs
+++ b/tests/compile-fail/regex.rs
@@ -1,8 +1,8 @@
 #![feature(plugin)]
-#![plugin(clippy)]
+#![plugin(clippy, regex_macros)]
 
 #![allow(unused)]
-#![deny(invalid_regex, trivial_regex)]
+#![deny(invalid_regex, trivial_regex, regex_macro)]
 
 extern crate regex;
 
@@ -70,7 +70,14 @@ fn trivial_regex() {
     let non_trivial_ends_with = Regex::new("foo|bar");
 }
 
+fn regex_macro() {
+    let some_regex = regex!("for real!"); //~ERROR `regex!(_)`
+    let other_regex = regex!("[a-z]_[A-Z]"); //~ERROR `regex!(_)`
+}
+
+
 fn main() {
+    regex_macro();
     syntax_error();
     trivial_regex();
 }