rebased

Author: merelymyself

CHANGELOG.md

@@ -3649,6 +3649,7 @@ Released 2018-09-13
 [`panicking_unwrap`]: https://rust-lang.github.io/rust-clippy/master/index.html#panicking_unwrap
 [`partialeq_ne_impl`]: https://rust-lang.github.io/rust-clippy/master/index.html#partialeq_ne_impl
 [`path_buf_push_overwrite`]: https://rust-lang.github.io/rust-clippy/master/index.html#path_buf_push_overwrite
+[`path_from_format`]: https://rust-lang.github.io/rust-clippy/master/index.html#path_from_format
 [`pattern_type_mismatch`]: https://rust-lang.github.io/rust-clippy/master/index.html#pattern_type_mismatch
 [`possible_missing_comma`]: https://rust-lang.github.io/rust-clippy/master/index.html#possible_missing_comma
 [`precedence`]: https://rust-lang.github.io/rust-clippy/master/index.html#precedence

clippy_lints/src/lib.register_lints.rs

@@ -435,6 +435,7 @@ store.register_lints(&[
     pass_by_ref_or_value::LARGE_TYPES_PASSED_BY_VALUE,
     pass_by_ref_or_value::TRIVIALLY_COPY_PASS_BY_REF,
     path_buf_push_overwrite::PATH_BUF_PUSH_OVERWRITE,
+    path_from_format::PATH_FROM_FORMAT,
     pattern_type_mismatch::PATTERN_TYPE_MISMATCH,
     precedence::PRECEDENCE,
     ptr::CMP_NULL,

clippy_lints/src/lib.register_pedantic.rs

@@ -76,6 +76,7 @@ store.register_group(true, "clippy::pedantic", Some("clippy_pedantic"), vec![
     LintId::of(non_expressive_names::SIMILAR_NAMES),
     LintId::of(pass_by_ref_or_value::LARGE_TYPES_PASSED_BY_VALUE),
     LintId::of(pass_by_ref_or_value::TRIVIALLY_COPY_PASS_BY_REF),
+    LintId::of(path_from_format::PATH_FROM_FORMAT),
     LintId::of(ranges::RANGE_MINUS_ONE),
     LintId::of(ranges::RANGE_PLUS_ONE),
     LintId::of(redundant_else::REDUNDANT_ELSE),

clippy_lints/src/lib.rs

@@ -339,6 +339,7 @@ mod panic_unimplemented;
 mod partialeq_ne_impl;
 mod pass_by_ref_or_value;
 mod path_buf_push_overwrite;
+mod path_from_format;
 mod pattern_type_mismatch;
 mod precedence;
 mod ptr;
@@ -906,6 +907,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|| Box::new(rc_clone_in_vec_init::RcCloneInVecInit));
     store.register_early_pass(|| Box::new(duplicate_mod::DuplicateMod::default()));
     store.register_late_pass(|| Box::new(get_first::GetFirst));
+    store.register_late_pass(|| Box::new(path_from_format::PathFromFormat));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }
 

clippy_lints/src/path_from_format.rs

@@ -0,0 +1,82 @@
+use clippy_utils::diagnostics::span_lint_and_help;
+use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::{match_qpath, paths, peel_hir_expr_refs};
+use rustc_hir::{StmtKind,BorrowKind, Mutability, BindingAnnotation, PatKind, Expr, ExprKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::sym;
+
+declare_clippy_lint! {
+    /// ### What it does
+    ///
+    /// ### Why is this bad?
+    ///
+    /// ### Example
+    /// ```rust
+    /// // example code where clippy issues a warning
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// // example code which does not raise clippy warning
+    /// ```
+    #[clippy::version = "1.62.0"]
+    pub PATH_FROM_FORMAT,
+    pedantic,
+    "default lint description"
+}
+
+declare_lint_pass!(PathFromFormat => [PATH_FROM_FORMAT]);
+
+impl<'tcx> LateLintPass<'tcx> for PathFromFormat {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+        if_chain! {
+            if let ExprKind::Call(func, args) = expr.kind;
+            if let ExprKind::Path(ref qpath) = func.kind;
+            if match_qpath(qpath, &["PathBuf", "from"]);
+            // if args.len() == 1;
+            if let Some(macro_def_id) = args[0].span.ctxt().outer_expn_data().macro_def_id;
+            if cx.tcx.get_diagnostic_name(macro_def_id) == Some(sym::format_macro);
+            // if let ExprKind::Block(block, None) = args[0].kind;
+            // if block.stmts.len() == 1;
+            // if let StmtKind::Local(local) = block.stmts[0].kind;
+            // if let Some(init) = local.init;
+            // if let ExprKind::Call(func1, args1) = init.kind;
+            // if let ExprKind::Path(ref qpath1) = func1.kind;
+            // if match_qpath(qpath1, &["$crate", "fmt", "format"]);
+            // if args1.len() == 1;
+            // if let ExprKind::Call(func2, args2) = args1[0].kind;
+            // if let ExprKind::Path(ref qpath2) = func2.kind;
+            // if match_qpath(qpath2, &["$crate", "fmt", "Arguments", "new_v1"]);
+            // if args2.len() == 2;
+            // if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner) = args2[0].kind;
+            // if let ExprKind::Array(elements) = inner.kind;
+            // if elements.len() == 2;
+            // if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner1) = args2[1].kind;
+            // if let ExprKind::Array(elements1) = inner1.kind;
+            // if elements1.len() == 1;
+            // if let ExprKind::Call(func3, args3) = elements1[0].kind;
+            // if let ExprKind::Path(ref qpath3) = func3.kind;
+            // if match_qpath(qpath3, &["$crate", "fmt", "ArgumentV1", "new_display"]);
+            // if args3.len() == 1;
+            // if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner2) = args3[0].kind;
+            // if let ExprKind::Path(ref qpath4) = inner2.kind;
+            // if match_qpath(qpath4, &["base_path"]);
+            // if let PatKind::Binding(BindingAnnotation::Unannotated, _, name, None) = local.pat.kind;
+            // if name.as_str() == "res";
+            // if let Some(trailing_expr) = block.expr;
+            // if let ExprKind::Path(ref qpath5) = trailing_expr.kind;
+            // if match_qpath(qpath5, &["res"]);
+            then {    
+                span_lint_and_help(
+                    cx,
+                    PATH_FROM_FORMAT,
+                    expr.span,
+                    "`format!(..)` used to form `PathBuf`",
+                    None,
+                    "consider using `.join()` or `.push()` to avoid the extra allocation",
+                );
+               // report your lint here
+            }
+        }
+    }
+}   

tests/ui/path_from_format.rs

@@ -0,0 +1,10 @@
+#![warn(clippy::path_from_format)]
+
+use std::path::PathBuf;
+
+fn main() {
+    // let base_path = "";
+    // PathBuf::from(format!("{}/foo/bar", base_path));  
+    let mut base_path1 = "";
+    PathBuf::from(format!("{}/foo/bar", base_path1)); 
+}

tests/ui/path_from_format.stderr

@@ -0,0 +1,11 @@
+error: `format!(..)` used to form `PathBuf`
+  --> $DIR/path_from_format.rs:9:5
+   |
+LL |     PathBuf::from(format!("{}/foo/bar", base_path1)); 
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::path-from-format` implied by `-D warnings`
+   = help: consider using `.join()` or `.push()` to avoid the extra allocation
+
+error: aborting due to previous error
+