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utils: extract utility method for matching trait method calls from loops

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This commit is contained in:
Georg Brandl 2015-08-23 16:32:50 +02:00
parent 5a5b1ba96b
commit c8a2e848ab
2 changed files with 18 additions and 12 deletions
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11
src/loops.rs
View File

@ -1,10 +1,9 @@
use rustc::lint::*; use rustc::lint::*;
use syntax::ast::*; use syntax::ast::*;
use syntax::visit::{Visitor, walk_expr}; use syntax::visit::{Visitor, walk_expr};
use rustc::middle::ty;
use std::collections::HashSet; use std::collections::HashSet;
use utils::{snippet, span_lint, get_parent_expr, match_def_path}; use utils::{snippet, span_lint, get_parent_expr, match_trait_method};
declare_lint!{ pub NEEDLESS_RANGE_LOOP, Warn, declare_lint!{ pub NEEDLESS_RANGE_LOOP, Warn,
"for-looping over a range of indices where an iterator over items would do" } "for-looping over a range of indices where an iterator over items would do" }
@ -68,12 +67,7 @@ impl LintPass for LoopsPass {
object, object)); object, object));
// check for looping over Iterator::next() which is not what you want // check for looping over Iterator::next() which is not what you want
} else if method_name == "next" { } else if method_name == "next" {
let method_call = ty::MethodCall::expr(arg.id); if match_trait_method(cx, arg, &["core", "iter", "Iterator"]) {
let trt_id = cx.tcx.tables
.borrow().method_map.get(&method_call)
.and_then(|callee| cx.tcx.trait_of_item(callee.def_id));
if let Some(trt_id) = trt_id {
if match_def_path(cx, trt_id, &["core", "iter", "Iterator"]) {
span_lint(cx, ITER_NEXT_LOOP, expr.span, span_lint(cx, ITER_NEXT_LOOP, expr.span,
"you are iterating over `Iterator::next()` which is an Option; \ "you are iterating over `Iterator::next()` which is an Option; \
this will compile but is probably not what you want"); this will compile but is probably not what you want");
@ -84,7 +78,6 @@ impl LintPass for LoopsPass {
} }
} }
} }
}
/// Recover the essential nodes of a desugared for loop: /// Recover the essential nodes of a desugared for loop:
/// `for pat in arg { body }` becomes `(pat, arg, body)`. /// `for pat in arg { body }` becomes `(pat, arg, body)`.

13
src/utils.rs
View File

@ -56,6 +56,19 @@ pub fn match_type(cx: &Context, ty: ty::Ty, path: &[&str]) -> bool {
} }
} }
/// check if method call given in "expr" belongs to given trait
pub fn match_trait_method(cx: &Context, expr: &Expr, path: &[&str]) -> bool {
let method_call = ty::MethodCall::expr(expr.id);
let trt_id = cx.tcx.tables
.borrow().method_map.get(&method_call)
.and_then(|callee| cx.tcx.trait_of_item(callee.def_id));
if let Some(trt_id) = trt_id {
match_def_path(cx, trt_id, path)
} else {
false
}
}
/// match a Path against a slice of segment string literals, e.g. /// match a Path against a slice of segment string literals, e.g.
/// `match_path(path, &["std", "rt", "begin_unwind"])` /// `match_path(path, &["std", "rt", "begin_unwind"])`
pub fn match_path(path: &Path, segments: &[&str]) -> bool { pub fn match_path(path: &Path, segments: &[&str]) -> bool {