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Auto merge of #7442 - camsteffen:format-args, r=xFrednet
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Refactor `format_args!` expansion parsing

Introduces `FormatExpn::parse` and `FormatArgsExpn::parse`. Motivated by rust-lang/rust#83302, so I only have to change Clippy in one place. Fixed an FP along the way.

I also allowed `needless_bool` in macros because I often want to do `if_chain! { .. then { true } else { false } }`.

changelog: Fix false positive in `useless_format` when some text is appended or prepended to a single string with some useless formatting params
changelog: Allow `needless_bool` in macros
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@bors
bors committed Jul 13, 2021
2 parents 94d6be4 + 306f9e8 commit bf4512e
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Showing 9 changed files with 238 additions and 265 deletions.
117 changes: 36 additions & 81 deletions clippy_lints/src/explicit_write.rs
View file
Original file line number Diff line number Diff line change
@@ -1,9 +1,9 @@
use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg};
use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_sugg};
use clippy_utils::higher::FormatArgsExpn;
use clippy_utils::{is_expn_of, match_function_call, paths};
use if_chain::if_chain;
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
use rustc_hir::{BorrowKind, Expr, ExprKind};
use rustc_hir::{Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::sym;
Expand Down Expand Up @@ -34,29 +34,26 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitWrite {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if_chain! {
// match call to unwrap
if let ExprKind::MethodCall(unwrap_fun, _, unwrap_args, _) = expr.kind;
if let ExprKind::MethodCall(unwrap_fun, _, [write_call], _) = expr.kind;
if unwrap_fun.ident.name == sym::unwrap;
// match call to write_fmt
if !unwrap_args.is_empty();
if let ExprKind::MethodCall(write_fun, _, write_args, _) =
unwrap_args[0].kind;
if let ExprKind::MethodCall(write_fun, _, [write_recv, write_arg], _) = write_call.kind;
if write_fun.ident.name == sym!(write_fmt);
// match calls to std::io::stdout() / std::io::stderr ()
if !write_args.is_empty();
if let Some(dest_name) = if match_function_call(cx, &write_args[0], &paths::STDOUT).is_some() {
if let Some(dest_name) = if match_function_call(cx, write_recv, &paths::STDOUT).is_some() {
Some("stdout")
} else if match_function_call(cx, &write_args[0], &paths::STDERR).is_some() {
} else if match_function_call(cx, write_recv, &paths::STDERR).is_some() {
Some("stderr")
} else {
None
};
if let Some(format_args) = FormatArgsExpn::parse(write_arg);
then {
let write_span = unwrap_args[0].span;
let calling_macro =
// ordering is important here, since `writeln!` uses `write!` internally
if is_expn_of(write_span, "writeln").is_some() {
if is_expn_of(write_call.span, "writeln").is_some() {
Some("writeln")
} else if is_expn_of(write_span, "write").is_some() {
} else if is_expn_of(write_call.span, "write").is_some() {
Some("write")
} else {
None
Expand All @@ -70,82 +67,40 @@ impl<'tcx> LateLintPass<'tcx> for ExplicitWrite {
// We need to remove the last trailing newline from the string because the
// underlying `fmt::write` function doesn't know whether `println!` or `print!` was
// used.
if let Some(mut write_output) = write_output_string(write_args) {
let (used, sugg_mac) = if let Some(macro_name) = calling_macro {
(
format!("{}!({}(), ...)", macro_name, dest_name),
macro_name.replace("write", "print"),
)
} else {
(
format!("{}().write_fmt(...)", dest_name),
"print".into(),
)
};
let msg = format!("use of `{}.unwrap()`", used);
if let [write_output] = *format_args.format_string_symbols {
let mut write_output = write_output.to_string();
if write_output.ends_with('\n') {
write_output.pop();
}

if let Some(macro_name) = calling_macro {
span_lint_and_sugg(
cx,
EXPLICIT_WRITE,
expr.span,
&format!(
"use of `{}!({}(), ...).unwrap()`",
macro_name,
dest_name
),
"try this",
format!("{}{}!(\"{}\")", prefix, macro_name.replace("write", "print"), write_output.escape_default()),
Applicability::MachineApplicable
);
} else {
span_lint_and_sugg(
cx,
EXPLICIT_WRITE,
expr.span,
&format!("use of `{}().write_fmt(...).unwrap()`", dest_name),
"try this",
format!("{}print!(\"{}\")", prefix, write_output.escape_default()),
Applicability::MachineApplicable
);
}
let sugg = format!("{}{}!(\"{}\")", prefix, sugg_mac, write_output.escape_default());
span_lint_and_sugg(
cx,
EXPLICIT_WRITE,
expr.span,
&msg,
"try this",
sugg,
Applicability::MachineApplicable
);
} else {
// We don't have a proper suggestion
if let Some(macro_name) = calling_macro {
span_lint(
cx,
EXPLICIT_WRITE,
expr.span,
&format!(
"use of `{}!({}(), ...).unwrap()`. Consider using `{}{}!` instead",
macro_name,
dest_name,
prefix,
macro_name.replace("write", "print")
)
);
} else {
span_lint(
cx,
EXPLICIT_WRITE,
expr.span,
&format!("use of `{}().write_fmt(...).unwrap()`. Consider using `{}print!` instead", dest_name, prefix),
);
}
let help = format!("consider using `{}{}!` instead", prefix, sugg_mac);
span_lint_and_help(cx, EXPLICIT_WRITE, expr.span, &msg, None, &help);
}

}
}
}
}

// Extract the output string from the given `write_args`.
fn write_output_string(write_args: &[Expr<'_>]) -> Option<String> {
if_chain! {
// Obtain the string that should be printed
if write_args.len() > 1;
if let ExprKind::Call(_, output_args) = write_args[1].kind;
if !output_args.is_empty();
if let ExprKind::AddrOf(BorrowKind::Ref, _, output_string_expr) = output_args[0].kind;
if let ExprKind::Array(string_exprs) = output_string_expr.kind;
// we only want to provide an automatic suggestion for simple (non-format) strings
if string_exprs.len() == 1;
if let ExprKind::Lit(ref lit) = string_exprs[0].kind;
if let LitKind::Str(ref write_output, _) = lit.node;
then {
return Some(write_output.to_string())
}
}
None
}
192 changes: 69 additions & 123 deletions clippy_lints/src/format.rs
View file
Original file line number Diff line number Diff line change
@@ -1,17 +1,16 @@
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::paths;
use clippy_utils::source::{snippet, snippet_opt};
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::higher::FormatExpn;
use clippy_utils::last_path_segment;
use clippy_utils::source::{snippet_opt, snippet_with_applicability};
use clippy_utils::sugg::Sugg;
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::{is_expn_of, last_path_segment, match_def_path, match_function_call};
use if_chain::if_chain;
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
use rustc_hir::{Arm, BorrowKind, Expr, ExprKind, MatchSource, PatKind};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_hir::{BorrowKind, Expr, ExprKind, QPath};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::Span;
use rustc_span::sym;
use rustc_span::symbol::kw;
use rustc_span::{sym, Span};

declare_clippy_lint! {
/// **What it does:** Checks for the use of `format!("string literal with no
Expand Down Expand Up @@ -44,130 +43,78 @@ declare_lint_pass!(UselessFormat => [USELESS_FORMAT]);

impl<'tcx> LateLintPass<'tcx> for UselessFormat {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
let span = match is_expn_of(expr.span, "format") {
Some(s) if !s.from_expansion() => s,
let FormatExpn { call_site, format_args } = match FormatExpn::parse(expr) {
Some(e) if !e.call_site.from_expansion() => e,
_ => return,
};

// Operate on the only argument of `alloc::fmt::format`.
if let Some(sugg) = on_new_v1(cx, expr) {
span_useless_format(cx, span, "consider using `.to_string()`", sugg);
} else if let Some(sugg) = on_new_v1_fmt(cx, expr) {
span_useless_format(cx, span, "consider using `.to_string()`", sugg);
}
}
}

fn span_useless_format<T: LintContext>(cx: &T, span: Span, help: &str, mut sugg: String) {
let to_replace = span.source_callsite();

// The callsite span contains the statement semicolon for some reason.
let snippet = snippet(cx, to_replace, "..");
if snippet.ends_with(';') {
sugg.push(';');
}

span_lint_and_then(cx, USELESS_FORMAT, span, "useless use of `format!`", |diag| {
diag.span_suggestion(
to_replace,
help,
sugg,
Applicability::MachineApplicable, // snippet
);
});
}

fn on_argumentv1_new<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) -> Option<String> {
if_chain! {
if let ExprKind::AddrOf(BorrowKind::Ref, _, format_args) = expr.kind;
if let ExprKind::Array(elems) = arms[0].body.kind;
if elems.len() == 1;
if let Some(args) = match_function_call(cx, &elems[0], &paths::FMT_ARGUMENTV1_NEW);
// matches `core::fmt::Display::fmt`
if args.len() == 2;
if let ExprKind::Path(ref qpath) = args[1].kind;
if let Some(did) = cx.qpath_res(qpath, args[1].hir_id).opt_def_id();
if match_def_path(cx, did, &paths::DISPLAY_FMT_METHOD);
// check `(arg0,)` in match block
if let PatKind::Tuple(pats, None) = arms[0].pat.kind;
if pats.len() == 1;
then {
let ty = cx.typeck_results().pat_ty(pats[0]).peel_refs();
if *ty.kind() != rustc_middle::ty::Str && !is_type_diagnostic_item(cx, ty, sym::string_type) {
return None;
}
if let ExprKind::Lit(ref lit) = format_args.kind {
if let LitKind::Str(ref s, _) = lit.node {
return Some(format!("{:?}.to_string()", s.as_str()));
let mut applicability = Applicability::MachineApplicable;
if format_args.value_args.is_empty() {
if_chain! {
if let [e] = &*format_args.format_string_parts;
if let ExprKind::Lit(lit) = &e.kind;
if let Some(s_src) = snippet_opt(cx, lit.span);
then {
// Simulate macro expansion, converting {{ and }} to { and }.
let s_expand = s_src.replace("{{", "{").replace("}}", "}");
let sugg = format!("{}.to_string()", s_expand);
span_useless_format(cx, call_site, sugg, applicability);
}
} else {
let sugg = Sugg::hir(cx, format_args, "<arg>");
if let ExprKind::MethodCall(path, _, _, _) = format_args.kind {
if path.ident.name == sym!(to_string) {
return Some(format!("{}", sugg));
}
} else if let ExprKind::Binary(..) = format_args.kind {
return Some(format!("{}", sugg));
}
} else if let [value] = *format_args.value_args {
if_chain! {
if format_args.format_string_symbols == [kw::Empty];
if match cx.typeck_results().expr_ty(value).peel_refs().kind() {
ty::Adt(adt, _) => cx.tcx.is_diagnostic_item(sym::string_type, adt.did),
ty::Str => true,
_ => false,
};
if format_args.args.iter().all(|e| is_display_arg(e));
if format_args.fmt_expr.map_or(true, |e| check_unformatted(e));
then {
let is_new_string = match value.kind {
ExprKind::Binary(..) => true,
ExprKind::MethodCall(path, ..) => path.ident.name.as_str() == "to_string",
_ => false,
};
let sugg = if is_new_string {
snippet_with_applicability(cx, value.span, "..", &mut applicability).into_owned()
} else {
let sugg = Sugg::hir_with_applicability(cx, value, "<arg>", &mut applicability);
format!("{}.to_string()", sugg.maybe_par())
};
span_useless_format(cx, call_site, sugg, applicability);
}
return Some(format!("{}.to_string()", sugg.maybe_par()));
}
}
};
}
None
}

fn on_new_v1<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<String> {
if_chain! {
if let Some(args) = match_function_call(cx, expr, &paths::FMT_ARGUMENTS_NEW_V1);
if args.len() == 2;
// Argument 1 in `new_v1()`
if let ExprKind::AddrOf(BorrowKind::Ref, _, arr) = args[0].kind;
if let ExprKind::Array(pieces) = arr.kind;
if pieces.len() == 1;
if let ExprKind::Lit(ref lit) = pieces[0].kind;
if let LitKind::Str(ref s, _) = lit.node;
// Argument 2 in `new_v1()`
if let ExprKind::AddrOf(BorrowKind::Ref, _, arg1) = args[1].kind;
if let ExprKind::Match(matchee, arms, MatchSource::Normal) = arg1.kind;
if arms.len() == 1;
if let ExprKind::Tup(tup) = matchee.kind;
then {
// `format!("foo")` expansion contains `match () { () => [], }`
if tup.is_empty() {
if let Some(s_src) = snippet_opt(cx, lit.span) {
// Simulate macro expansion, converting {{ and }} to { and }.
let s_expand = s_src.replace("{{", "{").replace("}}", "}");
return Some(format!("{}.to_string()", s_expand));
}
} else if s.as_str().is_empty() {
return on_argumentv1_new(cx, &tup[0], arms);
}
}
fn span_useless_format(cx: &LateContext<'_>, span: Span, mut sugg: String, mut applicability: Applicability) {
// The callsite span contains the statement semicolon for some reason.
if snippet_with_applicability(cx, span, "..", &mut applicability).ends_with(';') {
sugg.push(';');
}
None

span_lint_and_sugg(
cx,
USELESS_FORMAT,
span,
"useless use of `format!`",
"consider using `.to_string()`",
sugg,
applicability,
);
}

fn on_new_v1_fmt<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<String> {
fn is_display_arg(expr: &Expr<'_>) -> bool {
if_chain! {
if let Some(args) = match_function_call(cx, expr, &paths::FMT_ARGUMENTS_NEW_V1_FORMATTED);
if args.len() == 3;
if check_unformatted(&args[2]);
// Argument 1 in `new_v1_formatted()`
if let ExprKind::AddrOf(BorrowKind::Ref, _, arr) = args[0].kind;
if let ExprKind::Array(pieces) = arr.kind;
if pieces.len() == 1;
if let ExprKind::Lit(ref lit) = pieces[0].kind;
if let LitKind::Str(..) = lit.node;
// Argument 2 in `new_v1_formatted()`
if let ExprKind::AddrOf(BorrowKind::Ref, _, arg1) = args[1].kind;
if let ExprKind::Match(matchee, arms, MatchSource::Normal) = arg1.kind;
if arms.len() == 1;
if let ExprKind::Tup(tup) = matchee.kind;
then {
return on_argumentv1_new(cx, &tup[0], arms);
}
if let ExprKind::Call(_, [_, fmt]) = expr.kind;
if let ExprKind::Path(QPath::Resolved(_, path)) = fmt.kind;
if let [.., t, _] = path.segments;
if t.ident.name.as_str() == "Display";
then { true } else { false }
}
None
}

/// Checks if the expression matches
Expand All @@ -184,10 +131,9 @@ fn on_new_v1_fmt<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<S
fn check_unformatted(expr: &Expr<'_>) -> bool {
if_chain! {
if let ExprKind::AddrOf(BorrowKind::Ref, _, expr) = expr.kind;
if let ExprKind::Array(exprs) = expr.kind;
if exprs.len() == 1;
if let ExprKind::Array([expr]) = expr.kind;
// struct `core::fmt::rt::v1::Argument`
if let ExprKind::Struct(_, fields, _) = exprs[0].kind;
if let ExprKind::Struct(_, fields, _) = expr.kind;
if let Some(format_field) = fields.iter().find(|f| f.ident.name == sym::format);
// struct `core::fmt::rt::v1::FormatSpec`
if let ExprKind::Struct(_, fields, _) = format_field.expr.kind;
Expand Down
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