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Added final lint and tests

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This commit is contained in:
pmk21 2020-04-06 23:40:41 +05:30
parent 7c52e51d79
commit 4d03b4d2f0
4 changed files with 660 additions and 44 deletions
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151
clippy_lints/src/implicit_saturating_sub.rs
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@ -1,4 +1,4 @@
use crate::utils::{higher, in_macro, span_lint_and_sugg};
use crate::utils::{higher, in_macro, match_qpath, span_lint_and_sugg, SpanlessEq};
use if_chain::if_chain;
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
@ -9,17 +9,17 @@ use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
/// **What it does:** Checks for implicit saturating subtraction.
///
/// **Why is this bad?** Simplicity and readability. Instead we can easily use an inbuilt function.
/// **Why is this bad?** Simplicity and readability. Instead we can easily use an builtin function.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust
/// let end = 10;
/// let start = 5;
/// let end: u32 = 10;
/// let start: u32 = 5;
///
/// let mut i = end - start;
/// let mut i: u32 = end - start;
///
/// // Bad
/// if i != 0 {
@ -28,13 +28,13 @@ declare_clippy_lint! {
/// ```
/// Use instead:
/// ```rust
/// let end = 10;
/// let start = 5;
/// let end: u32 = 10;
/// let start: u32 = 5;
///
/// let mut i = end - start;
/// let mut i: u32 = end - start;
///
/// // Good
/// i.saturating_sub(1);
/// i = i.saturating_sub(1);
/// ```
pub IMPLICIT_SATURATING_SUB,
pedantic,
@ -50,41 +50,124 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitSaturatingSub {
}
if_chain! {
if let Some((ref cond, ref then, None)) = higher::if_block(&expr);
// Check if the conditional expression is a binary operation
if let ExprKind::Binary(ref op, ref left, ref right) = cond.kind;
// Ensure that the binary operator is > or !=
if BinOpKind::Ne == op.node || BinOpKind::Gt == op.node;
if let ExprKind::Path(ref cond_path) = left.kind;
// Get the literal on the right hand side
if let ExprKind::Lit(ref lit) = right.kind;
if let LitKind::Int(0, _) = lit.node;
if let ExprKind::Binary(ref cond_op, ref cond_left, ref cond_right) = cond.kind;
// Ensure that the binary operator is >, != and <
if BinOpKind::Ne == cond_op.node || BinOpKind::Gt == cond_op.node || BinOpKind::Lt == cond_op.node;
// Check if the true condition block has only one statement
if let ExprKind::Block(ref block, _) = then.kind;
if block.stmts.len() == 1;
if block.stmts.len() == 1 && block.expr.is_none();
// Check if assign operation is done
if let StmtKind::Semi(ref e) = block.stmts[0].kind;
if let ExprKind::AssignOp(ref op1, ref target, ref value) = e.kind;
if BinOpKind::Sub == op1.node;
if let Some(target) = subtracts_one(cx, e);
// Extracting out the variable name
if let ExprKind::Path(ref assign_path) = target.kind;
// Check if the variable in the condition and assignment statement are the same
if let (QPath::Resolved(_, ref cres_path), QPath::Resolved(_, ref ares_path)) = (cond_path, assign_path);
if cres_path.res == ares_path.res;
if let ExprKind::Lit(ref lit1) = value.kind;
if let LitKind::Int(assign_lit, _) = lit1.node;
if let QPath::Resolved(_, ref ares_path) = assign_path;
then {
// Handle symmetric conditions in the if statement
let (cond_var, cond_num_val) = if SpanlessEq::new(cx).eq_expr(cond_left, target) {
if BinOpKind::Gt == cond_op.node || BinOpKind::Ne == cond_op.node {
(cond_left, cond_right)
} else {
return;
}
} else if SpanlessEq::new(cx).eq_expr(cond_right, target) {
if BinOpKind::Lt == cond_op.node || BinOpKind::Ne == cond_op.node {
(cond_right, cond_left)
} else {
return;
}
} else {
return;
};
// Check if the variable in the condition statement is an integer
if !cx.tables.expr_ty(cond_var).is_integral() {
return;
}
// Get the variable name
let var_name = ares_path.segments[0].ident.name.as_str();
let applicability = Applicability::MaybeIncorrect;
span_lint_and_sugg(
cx,
IMPLICIT_SATURATING_SUB,
expr.span,
"Implicitly performing saturating subtraction",
"try",
format!("{}.saturating_sub({});", var_name, assign_lit.to_string()),
applicability
);
const INT_TYPES: [&str; 5] = ["i8", "i16", "i32", "i64", "i128"];
match cond_num_val.kind {
ExprKind::Lit(ref cond_lit) => {
// Check if the constant is zero
if let LitKind::Int(0, _) = cond_lit.node {
if cx.tables.expr_ty(cond_left).is_signed() {
} else {
print_lint_and_sugg(cx, &var_name, expr);
};
}
},
ExprKind::Path(ref cond_num_path) => {
if INT_TYPES.iter().any(|int_type| match_qpath(cond_num_path, &[int_type, "MIN"])) {
print_lint_and_sugg(cx, &var_name, expr);
};
},
ExprKind::Call(ref func, _) => {
if let ExprKind::Path(ref cond_num_path) = func.kind {
if INT_TYPES.iter().any(|int_type| match_qpath(cond_num_path, &[int_type, "min_value"])) {
print_lint_and_sugg(cx, &var_name, expr);
}
};
},
_ => (),
}
}
}
}
}
fn subtracts_one<'a>(cx: &LateContext<'_, '_>, expr: &Expr<'a>) -> Option<&'a Expr<'a>> {
match expr.kind {
ExprKind::AssignOp(ref op1, ref target, ref value) => {
if_chain! {
if BinOpKind::Sub == op1.node;
// Check if literal being subtracted is one
if let ExprKind::Lit(ref lit1) = value.kind;
if let LitKind::Int(1, _) = lit1.node;
then {
Some(target)
} else {
None
}
}
},
ExprKind::Assign(ref target, ref value, _) => {
if_chain! {
if let ExprKind::Binary(ref op1, ref left1, ref right1) = value.kind;
if BinOpKind::Sub == op1.node;
if SpanlessEq::new(cx).eq_expr(left1, target);
if let ExprKind::Lit(ref lit1) = right1.kind;
if let LitKind::Int(1, _) = lit1.node;
then {
Some(target)
} else {
None
}
}
},
_ => None,
}
}
fn print_lint_and_sugg(cx: &LateContext<'_, '_>, var_name: &str, expr: &Expr<'_>) {
span_lint_and_sugg(
cx,
IMPLICIT_SATURATING_SUB,
expr.span,
"Implicitly performing saturating subtraction",
"try",
format!("{} = {}.saturating_sub({});", var_name, var_name, 1.to_string()),
Applicability::MachineApplicable,
);
}