Auto merge of rust-lang#9289 - mkrasnitski:9094, r=xFrednet

Extend `if_then_some_else_none` to also suggest `bool::then_some` Closes rust-lang#9094. changelog: Extend `if_then_some_else_none` to also suggest `bool::then_some`
Jarcho · Aug 12, 2022 · 05fc1c7 · 05fc1c7
2 parents 2b2190c + f7f60b8
commit 05fc1c7
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diff --git a/clippy_lints/src/if_then_some_else_none.rs b/clippy_lints/src/if_then_some_else_none.rs
@@ -1,7 +1,7 @@
 use clippy_utils::diagnostics::span_lint_and_help;
+use clippy_utils::eager_or_lazy::switch_to_eager_eval;
 use clippy_utils::source::snippet_with_macro_callsite;
 use clippy_utils::{contains_return, higher, is_else_clause, is_lang_ctor, meets_msrv, msrvs, peel_blocks};
-use if_chain::if_chain;
 use rustc_hir::LangItem::{OptionNone, OptionSome};
 use rustc_hir::{Expr, ExprKind, Stmt, StmtKind};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
@@ -11,10 +11,12 @@ use rustc_session::{declare_tool_lint, impl_lint_pass};
 
 declare_clippy_lint! {
     /// ### What it does
-    /// Checks for if-else that could be written to `bool::then`.
+    /// Checks for if-else that could be written using either `bool::then` or `bool::then_some`.
     ///
     /// ### Why is this bad?
-    /// Looks a little redundant. Using `bool::then` helps it have less lines of code.
+    /// Looks a little redundant. Using `bool::then` is more concise and incurs no loss of clarity.
+    /// For simple calculations and known values, use `bool::then_some`, which is eagerly evaluated
+    /// in comparison to `bool::then`.
     ///
     /// ### Example
     /// ```rust
@@ -39,7 +41,7 @@ declare_clippy_lint! {
     #[clippy::version = "1.53.0"]
     pub IF_THEN_SOME_ELSE_NONE,
     restriction,
-    "Finds if-else that could be written using `bool::then`"
+    "Finds if-else that could be written using either `bool::then` or `bool::then_some`"
 }
 
 pub struct IfThenSomeElseNone {
@@ -56,7 +58,7 @@ impl IfThenSomeElseNone {
 impl_lint_pass!(IfThenSomeElseNone => [IF_THEN_SOME_ELSE_NONE]);
 
 impl<'tcx> LateLintPass<'tcx> for IfThenSomeElseNone {
-    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &'tcx Expr<'_>) {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
         if !meets_msrv(self.msrv, msrvs::BOOL_THEN) {
             return;
         }
@@ -70,43 +72,47 @@ impl<'tcx> LateLintPass<'tcx> for IfThenSomeElseNone {
             return;
         }
 
-        if_chain! {
-            if let Some(higher::If { cond, then, r#else: Some(els) }) = higher::If::hir(expr);
-            if let ExprKind::Block(then_block, _) = then.kind;
-            if let Some(then_expr) = then_block.expr;
-            if let ExprKind::Call(then_call, [then_arg]) = then_expr.kind;
-            if let ExprKind::Path(ref then_call_qpath) = then_call.kind;
-            if is_lang_ctor(cx, then_call_qpath, OptionSome);
-            if let ExprKind::Path(ref qpath) = peel_blocks(els).kind;
-            if is_lang_ctor(cx, qpath, OptionNone);
-            if !stmts_contains_early_return(then_block.stmts);
-            then {
-                let cond_snip = snippet_with_macro_callsite(cx, cond.span, "[condition]");
-                let cond_snip = if matches!(cond.kind, ExprKind::Unary(_, _) | ExprKind::Binary(_, _, _)) {
-                    format!("({})", cond_snip)
-                } else {
-                    cond_snip.into_owned()
-                };
-                let arg_snip = snippet_with_macro_callsite(cx, then_arg.span, "");
-                let closure_body = if then_block.stmts.is_empty() {
-                    arg_snip.into_owned()
-                } else {
-                    format!("{{ /* snippet */ {} }}", arg_snip)
-                };
-                let help = format!(
-                    "consider using `bool::then` like: `{}.then(|| {})`",
-                    cond_snip,
-                    closure_body,
-                );
-                span_lint_and_help(
-                    cx,
-                    IF_THEN_SOME_ELSE_NONE,
-                    expr.span,
-                    "this could be simplified with `bool::then`",
-                    None,
-                    &help,
-                );
-            }
+        if let Some(higher::If { cond, then, r#else: Some(els) }) = higher::If::hir(expr)
+            && let ExprKind::Block(then_block, _) = then.kind
+            && let Some(then_expr) = then_block.expr
+            && let ExprKind::Call(then_call, [then_arg]) = then_expr.kind
+            && let ExprKind::Path(ref then_call_qpath) = then_call.kind
+            && is_lang_ctor(cx, then_call_qpath, OptionSome)
+            && let ExprKind::Path(ref qpath) = peel_blocks(els).kind
+            && is_lang_ctor(cx, qpath, OptionNone)
+            && !stmts_contains_early_return(then_block.stmts)
+        {
+            let cond_snip = snippet_with_macro_callsite(cx, cond.span, "[condition]");
+            let cond_snip = if matches!(cond.kind, ExprKind::Unary(_, _) | ExprKind::Binary(_, _, _)) {
+                format!("({})", cond_snip)
+            } else {
+                cond_snip.into_owned()
+            };
+            let arg_snip = snippet_with_macro_callsite(cx, then_arg.span, "");
+            let mut method_body = if then_block.stmts.is_empty() {
+                arg_snip.into_owned()
+            } else {
+                format!("{{ /* snippet */ {} }}", arg_snip)
+            };
+            let method_name = if switch_to_eager_eval(cx, expr) && meets_msrv(self.msrv, msrvs::BOOL_THEN_SOME) {
+                "then_some"
+            } else {
+                method_body.insert_str(0, "|| ");
+                "then"
+            };
+
+            let help = format!(
+                "consider using `bool::{}` like: `{}.{}({})`",
+                method_name, cond_snip, method_name, method_body,
+            );
+            span_lint_and_help(
+                cx,
+                IF_THEN_SOME_ELSE_NONE,
+                expr.span,
+                &format!("this could be simplified with `bool::{}`", method_name),
+                None,
+                &help,
+            );
         }
     }
 

diff --git a/tests/ui/if_then_some_else_none.stderr b/tests/ui/if_then_some_else_none.stderr
@@ -27,21 +27,21 @@ LL | |     };
    |
    = help: consider using `bool::then` like: `matches!(true, true).then(|| { /* snippet */ matches!(true, false) })`
 
-error: this could be simplified with `bool::then`
+error: this could be simplified with `bool::then_some`
   --> $DIR/if_then_some_else_none.rs:23:28
    |
 LL |     let _ = x.and_then(|o| if o < 32 { Some(o) } else { None });
    |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: consider using `bool::then` like: `(o < 32).then(|| o)`
+   = help: consider using `bool::then_some` like: `(o < 32).then_some(o)`
 
-error: this could be simplified with `bool::then`
+error: this could be simplified with `bool::then_some`
   --> $DIR/if_then_some_else_none.rs:27:13
    |
 LL |     let _ = if !x { Some(0) } else { None };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: consider using `bool::then` like: `(!x).then(|| 0)`
+   = help: consider using `bool::then_some` like: `(!x).then_some(0)`
 
 error: this could be simplified with `bool::then`
   --> $DIR/if_then_some_else_none.rs:82:13