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Make if_chain more readable

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This commit is contained in:
Matthias Seiffert 2019-10-06 20:10:30 +02:00
parent 72a5d7b612
commit d66acc23a9
1 changed files with 55 additions and 38 deletions
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93
clippy_lints/src/assertions_on_constants.rs
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@ -1,5 +1,6 @@
use crate::consts::{constant, Constant};
use crate::utils::{is_direct_expn_of, is_expn_of, match_qpath, span_help_and_lint};
use crate::utils::paths;
use crate::utils::{is_direct_expn_of, is_expn_of, match_def_path, resolve_node, span_help_and_lint};
use if_chain::if_chain;
use rustc::hir::*;
use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
@ -99,59 +100,75 @@ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
}
}
// fn get_assert_args(snip: String) -> Option<Vec<String>> {
//
// }
/// Check if the expression matches
///
/// ```rust,ignore
/// match { let _t = !c; _t } {
/// true => {
/// {
/// ::std::rt::begin_panic(message, _)
/// }
/// }
/// _ => { }
/// };
/// ```
///
/// where `message` is a string literal and `c` is a constant bool.
///
/// TODO extend this to match anything as message not just string literals
///
/// Returns the `message` argument of `begin_panic` and the value of `c` which is the
/// first argument of `assert!`.
fn assert_with_message<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) -> Option<(LocalInternedString, bool)> {
if_chain! {
if let ExprKind::Match(ref expr, ref arms, MatchSource::IfDesugar { contains_else_clause: false }) = expr.kind;
// match expr
if let ExprKind::Match(ref expr, ref arms, _) = expr.kind;
// matches { let _t = expr; _t }
if let ExprKind::DropTemps(ref expr) = expr.kind;
if let ExprKind::Unary(UnOp::UnNot, ref expr) = expr.kind;
//if let ExprKind::Lit(ref lit) = expr.kind;
// bind the first argument of the `assert!` macro
if let Some((Constant::Bool(is_true), _)) = constant(cx, cx.tables, expr);
//if is_true;
// match arms
// arm 1 pattern
if let PatKind::Lit(ref lit_expr) = arms[0].pat.kind;
if let ExprKind::Lit(ref lit) = lit_expr.kind;
if let LitKind::Bool(true) = lit.node;
//if let LitKind::Bool(true) = lit1.node;
// arm 1 block
if let ExprKind::Block(ref block1, _) = arms[0].body.kind;
if let Some(trailing_expr1) = &block1.expr;
if block1.stmts.len() == 0;
//
if let ExprKind::Block(ref actual_block1, _) = trailing_expr1.kind;
if let Some(block1_expr) = &actual_block1.expr;
if let ExprKind::Block(ref block, _) = arms[0].body.kind;
if block.stmts.len() == 0;
if let Some(block_expr) = &block.expr;
if let ExprKind::Block(ref inner_block, _) = block_expr.kind;
if let Some(begin_panic_call) = &inner_block.expr;
// function call
if let ExprKind::Call(ref func, ref args) = block1_expr.kind;
if let ExprKind::Path(ref path) = func.kind;
// ["{{root}}", "std", "rt", "begin_panic"] does not work
if match_qpath(path, &["$crate", "rt", "begin_panic"]);
// arguments
if let Some(args) = match_function_call(cx, begin_panic_call, &paths::BEGIN_PANIC);
if args.len() == 2;
if let ExprKind::Lit(ref lit) = args[0].kind;
if let LitKind::Str(ref s, _) = lit.node;
let panic_message = s.as_str(); // bind the panic message
if let ExprKind::AddrOf(MutImmutable, ref inner) = args[1].kind;
if let ExprKind::Tup(ref elements) = inner.kind;
if elements.len() == 3;
if let ExprKind::Lit(ref lit1) = elements[0].kind;
if let LitKind::Str(ref s1, _) = lit1.node;
if let ExprKind::Lit(ref lit2) = elements[1].kind;
if let LitKind::Int(_, _) = lit2.node;
if let ExprKind::Lit(ref lit3) = elements[2].kind;
if let LitKind::Int(_, _) = lit3.node;
// arm 2 block
if let PatKind::Wild = arms[1].pat.kind;
if let ExprKind::Block(ref block2, _) = arms[1].body.kind;
if let None = &block2.expr;
if block2.stmts.len() == 0;
// bind the second argument of the `assert!` macro
let panic_message = s.as_str();
// second argument of begin_panic is irrelevant
// as is the second match arm
then {
return Some((panic_message, is_true));
}
}
return None;
None
}
/// Matches a function call with the given path and returns the arguments.
///
/// Usage:
///
/// ```rust,ignore
/// if let Some(args) = match_function_call(cx, begin_panic_call, &paths::BEGIN_PANIC);
/// ```
fn match_function_call<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr, path: &[&str]) -> Option<&'a [Expr]> {
if_chain! {
if let ExprKind::Call(ref fun, ref args) = expr.kind;
if let ExprKind::Path(ref qpath) = fun.kind;
if let Some(fun_def_id) = resolve_node(cx, qpath, fun.hir_id).opt_def_id();
if match_def_path(cx, fun_def_id, path);
then {
return Some(&args)
}
};
None
}