Add lint for variable names that contain uppercase characters

Author: Palmer Cox

src/librustc/middle/lint.rs

@@ -80,6 +80,7 @@ pub enum Lint {
     NonCamelCaseTypes,
     NonUppercaseStatics,
     NonUppercasePatternStatics,
+    UppercaseVariables,
     UnnecessaryParens,
     TypeLimits,
     TypeOverflow,
@@ -208,7 +209,14 @@ static lint_table: &'static [(&'static str, LintSpec)] = &[
          default: warn
      }),
 
-    ("unnecessary_parens",
+    ("uppercase_variables",
+     LintSpec {
+         lint: UppercaseVariables,
+         desc: "variable names should start with a lowercase character",
+         default: warn
+     }),
+
+     ("unnecessary_parens",
      LintSpec {
         lint: UnnecessaryParens,
         desc: "`if`, `match`, `while` and `return` do not need parentheses",
@@ -1169,6 +1177,30 @@ fn check_pat_non_uppercase_statics(cx: &Context, p: &ast::Pat) {
     }
 }
 
+fn check_pat_uppercase_variable(cx: &Context, p: &ast::Pat) {
+    let def_map = cx.tcx.def_map.borrow();
+    match &p.node {
+        &ast::PatIdent(_, ref path, _) => {
+            match def_map.get().find(&p.id) {
+                Some(&ast::DefLocal(_, _)) | Some(&ast::DefBinding(_, _)) |
+                        Some(&ast::DefArg(_, _)) => {
+                    // last identifier alone is right choice for this lint.
+                    let ident = path.segments.last().unwrap().identifier;
+                    let s = token::get_ident(ident);
+                    if s.get().char_at(0).is_uppercase() {
+                        cx.span_lint(
+                            UppercaseVariables,
+                            path.span,
+                            "variable names should start with a lowercase character");
+                    }
+                }
+                _ => {}
+            }
+        }
+        _ => {}
+    }
+}
+
 fn check_unnecessary_parens_core(cx: &Context, value: &ast::Expr, msg: &str) {
     match value.node {
         ast::ExprParen(_) => {
@@ -1553,6 +1585,7 @@ impl<'a> Visitor<()> for Context<'a> {
 
     fn visit_pat(&mut self, p: &ast::Pat, _: ()) {
         check_pat_non_uppercase_statics(self, p);
+        check_pat_uppercase_variable(self, p);
         check_unused_mut_pat(self, p);
 
         visit::walk_pat(self, p, ());

src/test/compile-fail/lint-uppercase-variables.rs

@@ -0,0 +1,34 @@
+// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[deny(uppercase_variables)];
+
+use std::io::File;
+use std::io::IoError;
+
+fn test(Xx: uint) { //~ ERROR variable names should start with a lowercase character
+    println!("{}", Xx);
+}
+
+fn main() {
+    let Test: uint = 0; //~ ERROR variable names should start with a lowercase character
+    println!("{}", Test);
+
+    let mut f = File::open(&Path::new("something.txt"));
+    let mut buff = [0u8, ..16];
+    match f.read(buff) {
+        Ok(cnt) => println!("read this many bytes: {}", cnt),
+        Err(IoError{ kind: EndOfFile, .. }) => println!("Got end of file: {}", EndOfFile.to_str()),
+                        //~^ ERROR variable names should start with a lowercase character
+    }
+
+    test(1);
+}
+