Merge pull request #246 from Manishearth/macro

Improve macro checks

src/consts.rs

@@ -1,3 +1,5 @@
+#![allow(cast_possible_truncation)]
+
 use rustc::lint::Context;
 use rustc::middle::const_eval::lookup_const_by_id;
 use rustc::middle::def::PathResolution;

src/identity_op.rs

@@ -4,7 +4,7 @@
 
 use consts::{constant, is_negative};
 use consts::Constant::ConstantInt;
-use utils::{span_lint, snippet};
+use utils::{span_lint, snippet, in_external_macro};
 
 declare_lint! { pub IDENTITY_OP, Warn,
                 "using identity operations, e.g. `x + 0` or `y / 1`" }
@@ -53,6 +53,7 @@ fn check(cx: &Context, e: &Expr, m: i8, span: Span, arg: Span) {
                 1 => !is_negative(ty) && v == 1,
                 _ => unreachable!(),
             } {
+                if in_external_macro(cx, e.span) {return;}
                 span_lint(cx, IDENTITY_OP, span, &format!(
                     "the operation is ineffective. Consider reducing it to `{}`",
                    snippet(cx, arg, "..")));

src/matches.rs

@@ -3,7 +3,8 @@
 use syntax::ast::*;
 use std::borrow::Cow;
 
-use utils::{snippet, snippet_block, span_lint, span_help_and_lint};
+use utils::{snippet, snippet_block};
+use utils::{span_lint, span_help_and_lint, in_external_macro};
 
 declare_lint!(pub SINGLE_MATCH, Warn,
               "a match statement with a single nontrivial arm (i.e, where the other arm \
@@ -36,6 +37,7 @@ fn check_expr(&mut self, cx: &Context, expr: &Expr) {
                 // finally, we don't want any content in the second arm (unit or empty block)
                 is_unit_expr(&arms[1].body)
             {
+                if in_external_macro(cx, expr.span) {return;}
                 let body_code = snippet_block(cx, arms[0].body.span, "..");
                 let body_code = if let ExprBlock(_) = arms[0].body.node {
                     body_code

src/returns.rs

@@ -3,7 +3,7 @@
 use syntax::codemap::{Span, Spanned};
 use syntax::visit::FnKind;
 
-use utils::{span_lint, snippet, match_path};
+use utils::{span_lint, snippet, match_path, in_external_macro};
 
 declare_lint!(pub NEEDLESS_RETURN, Warn,
               "using a return statement like `return expr;` where an expression would suffice");
@@ -58,6 +58,7 @@ fn check_final_expr(&mut self, cx: &Context, expr: &Expr) {
     }
 
     fn emit_return_lint(&mut self, cx: &Context, spans: (Span, Span)) {
+        if in_external_macro(cx, spans.1) {return;}
         span_lint(cx, NEEDLESS_RETURN, spans.0, &format!(
             "unneeded return statement. Consider using `{}` \
              without the return and trailing semicolon",
@@ -84,6 +85,7 @@ fn check_let_return(&mut self, cx: &Context, block: &Block) {
     }
 
     fn emit_let_lint(&mut self, cx: &Context, lint_span: Span, note_span: Span) {
+        if in_external_macro(cx, note_span) {return;}
         span_lint(cx, LET_AND_RETURN, lint_span,
                   "returning the result of a let binding. \
                    Consider returning the expression directly.");

src/types.rs

@@ -5,9 +5,8 @@
 use syntax::codemap::Span;
 use syntax::visit::{FnKind, Visitor, walk_ty};
 use rustc::middle::ty;
-use syntax::codemap::ExpnInfo;
 
-use utils::{in_macro, match_type, snippet, span_lint, span_help_and_lint, in_external_macro};
+use utils::{match_type, snippet, span_lint, span_help_and_lint, in_external_macro};
 use utils::{LL_PATH, VEC_PATH};
 
 /// Handles all the linting of funky types
@@ -55,11 +54,11 @@ fn check_ty(&mut self, cx: &Context, ast_ty: &ast::Ty) {
               "creating a let binding to a value of unit type, which usually can't be used afterwards");
 
 
-fn check_let_unit(cx: &Context, decl: &Decl, info: Option<&ExpnInfo>) {
-    if in_macro(cx, info) { return; }
+fn check_let_unit(cx: &Context, decl: &Decl) {
     if let DeclLocal(ref local) = decl.node {
         let bindtype = &cx.tcx.pat_ty(&local.pat).sty;
         if *bindtype == ty::TyTuple(vec![]) {
+            if in_external_macro(cx, decl.span) { return; }
             span_lint(cx, LET_UNIT_VALUE, decl.span, &format!(
                 "this let-binding has unit value. Consider omitting `let {} =`",
                 snippet(cx, local.pat.span, "..")));
@@ -73,9 +72,7 @@ fn get_lints(&self) -> LintArray {
     }
 
     fn check_decl(&mut self, cx: &Context, decl: &Decl) {
-        cx.sess().codemap().with_expn_info(
-            decl.span.expn_id,
-            |info| check_let_unit(cx, decl, info));
+        check_let_unit(cx, decl)
     }
 }
 

src/utils.rs

@@ -1,6 +1,6 @@
 use rustc::lint::*;
 use syntax::ast::*;
-use syntax::codemap::{ExpnInfo, Span};
+use syntax::codemap::{ExpnInfo, Span, ExpnFormat};
 use rustc::ast_map::Node::NodeExpr;
 use rustc::middle::def_id::DefId;
 use rustc::middle::ty;
@@ -18,6 +18,14 @@
 pub fn in_macro(cx: &Context, opt_info: Option<&ExpnInfo>) -> bool {
     // no ExpnInfo = no macro
     opt_info.map_or(false, |info| {
+        if info.callee.format == ExpnFormat::CompilerExpansion {
+            if info.callee.name == "closure expansion" {
+                return false;
+            }
+        } else if info.callee.format == ExpnFormat::MacroAttribute {
+            // these are all plugins
+            return true;
+        }
         // no span for the callee = external macro
         info.callee.span.map_or(true, |span| {
             // no snippet = external macro or compiler-builtin expansion
@@ -31,6 +39,7 @@ pub fn in_macro(cx: &Context, opt_info: Option<&ExpnInfo>) -> bool {
 }
 
 /// invokes in_macro with the expansion info of the given span
+/// slightly heavy, try to use this after other checks have already happened
 pub fn in_external_macro(cx: &Context, span: Span) -> bool {
     cx.sess().codemap().with_expn_info(span.expn_id,
             |info| in_macro(cx, info))