81 lines
2.9 KiB
Rust
81 lines
2.9 KiB
Rust
//! This LintPass catches both string addition and string addition + assignment
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//!
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//! Note that since we have two lints where one subsumes the other, we try to
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//! disable the subsumed lint unless it has a higher level
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use rustc::lint::*;
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use syntax::ast::*;
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use syntax::codemap::Spanned;
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use eq_op::is_exp_equal;
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use utils::{match_type, span_help_and_lint, walk_ptrs_ty, get_parent_expr};
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use utils::STRING_PATH;
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declare_lint! {
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pub STRING_ADD_ASSIGN,
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Allow,
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"using `x = x + ..` where x is a `String`; suggests using `push_str()` instead"
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}
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declare_lint! {
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pub STRING_ADD,
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Allow,
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"using `x + ..` where x is a `String`; suggests using `push_str()` instead"
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}
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#[derive(Copy, Clone)]
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pub struct StringAdd;
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impl LintPass for StringAdd {
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fn get_lints(&self) -> LintArray {
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lint_array!(STRING_ADD, STRING_ADD_ASSIGN)
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}
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fn check_expr(&mut self, cx: &Context, e: &Expr) {
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if let &ExprBinary(Spanned{ node: BiAdd, .. }, ref left, _) = &e.node {
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if is_string(cx, left) {
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if let Allow = cx.current_level(STRING_ADD_ASSIGN) {
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// the string_add_assign is allow, so no duplicates
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} else {
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let parent = get_parent_expr(cx, e);
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if let Some(ref p) = parent {
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if let &ExprAssign(ref target, _) = &p.node {
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// avoid duplicate matches
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if is_exp_equal(cx, target, left) { return; }
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}
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}
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}
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span_help_and_lint(cx, STRING_ADD, e.span,
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"you added something to a string. \
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Consider using `String::push_str()` instead",
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"for further information see https://github.com/\
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Manishearth/rust-clippy/wiki#string_add")
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}
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} else if let &ExprAssign(ref target, ref src) = &e.node {
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if is_string(cx, target) && is_add(cx, src, target) {
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span_help_and_lint(cx, STRING_ADD_ASSIGN, e.span,
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"you assigned the result of adding something to this string. \
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Consider using `String::push_str()` instead",
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"for further information see https://github.com/\
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Manishearth/rust-clippy/wiki#string_add_assign")
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}
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}
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}
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}
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fn is_string(cx: &Context, e: &Expr) -> bool {
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match_type(cx, walk_ptrs_ty(cx.tcx.expr_ty(e)), &STRING_PATH)
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}
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fn is_add(cx: &Context, src: &Expr, target: &Expr) -> bool {
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match src.node {
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ExprBinary(Spanned{ node: BiAdd, .. }, ref left, _) =>
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is_exp_equal(cx, target, left),
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ExprBlock(ref block) => block.stmts.is_empty() &&
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block.expr.as_ref().map_or(false,
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|expr| is_add(cx, expr, target)),
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ExprParen(ref expr) => is_add(cx, expr, target),
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_ => false
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}
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}
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