let unnecessary_cast work for trivial non_literal expressions

clippy_lints/src/casts/unnecessary_cast.rs

@@ -31,8 +31,10 @@ pub(super) fn check<'tcx>(
         }
     }
 
+    let cast_str = snippet_opt(cx, cast_expr.span).unwrap_or_default();
+
     if let Some(lit) = get_numeric_literal(cast_expr) {
-        let literal_str = snippet_opt(cx, cast_expr.span).unwrap_or_default();
+        let literal_str = &cast_str;
 
         if_chain! {
             if let LitKind::Int(n, _) = lit.node;
@@ -50,39 +52,44 @@ pub(super) fn check<'tcx>(
 
         match lit.node {
             LitKind::Int(_, LitIntType::Unsuffixed) if cast_to.is_integral() => {
-                lint_unnecessary_cast(cx, expr, &literal_str, cast_from, cast_to);
+                lint_unnecessary_cast(cx, expr, literal_str, cast_from, cast_to);
+                return false;
             },
             LitKind::Float(_, LitFloatType::Unsuffixed) if cast_to.is_floating_point() => {
-                lint_unnecessary_cast(cx, expr, &literal_str, cast_from, cast_to);
+                lint_unnecessary_cast(cx, expr, literal_str, cast_from, cast_to);
+                return false;
+            },
+            LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::Float(_, LitFloatType::Unsuffixed) => {
+                return false;
             },
-            LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::Float(_, LitFloatType::Unsuffixed) => {},
             LitKind::Int(_, LitIntType::Signed(_) | LitIntType::Unsigned(_))
             | LitKind::Float(_, LitFloatType::Suffixed(_))
                 if cast_from.kind() == cast_to.kind() =>
             {
                 if let Some(src) = snippet_opt(cx, cast_expr.span) {
                     if let Some(num_lit) = NumericLiteral::from_lit_kind(&src, &lit.node) {
                         lint_unnecessary_cast(cx, expr, num_lit.integer, cast_from, cast_to);
+                        return true;
                     }
                 }
             },
-            _ => {
-                if cast_from.kind() == cast_to.kind() && !in_external_macro(cx.sess(), expr.span) {
-                    span_lint_and_sugg(
-                        cx,
-                        UNNECESSARY_CAST,
-                        expr.span,
-                        &format!("casting to the same type is unnecessary (`{cast_from}` -> `{cast_to}`)"),
-                        "try",
-                        literal_str,
-                        Applicability::MachineApplicable,
-                    );
-                    return true;
-                }
-            },
+            _ => {},
         }
     }
 
+    if cast_from.kind() == cast_to.kind() && !in_external_macro(cx.sess(), expr.span) {
+        span_lint_and_sugg(
+            cx,
+            UNNECESSARY_CAST,
+            expr.span,
+            &format!("casting to the same type is unnecessary (`{cast_from}` -> `{cast_to}`)"),
+            "try",
+            cast_str,
+            Applicability::MachineApplicable,
+        );
+        return true;
+    }
+
     false
 }
 

tests/ui/floating_point_exp.fixed

@@ -1,5 +1,6 @@
 // run-rustfix
 #![warn(clippy::imprecise_flops)]
+#![allow(clippy::unnecessary_cast)]
 
 fn main() {
     let x = 2f32;

tests/ui/floating_point_exp.rs

@@ -1,5 +1,6 @@
 // run-rustfix
 #![warn(clippy::imprecise_flops)]
+#![allow(clippy::unnecessary_cast)]
 
 fn main() {
     let x = 2f32;

tests/ui/floating_point_exp.stderr

@@ -1,31 +1,31 @@
 error: (e.pow(x) - 1) can be computed more accurately
-  --> $DIR/floating_point_exp.rs:6:13
+  --> $DIR/floating_point_exp.rs:7:13
    |
 LL |     let _ = x.exp() - 1.0;
    |             ^^^^^^^^^^^^^ help: consider using: `x.exp_m1()`
    |
    = note: `-D clippy::imprecise-flops` implied by `-D warnings`
 
 error: (e.pow(x) - 1) can be computed more accurately
-  --> $DIR/floating_point_exp.rs:7:13
+  --> $DIR/floating_point_exp.rs:8:13
    |
 LL |     let _ = x.exp() - 1.0 + 2.0;
    |             ^^^^^^^^^^^^^ help: consider using: `x.exp_m1()`
 
 error: (e.pow(x) - 1) can be computed more accurately
-  --> $DIR/floating_point_exp.rs:8:13
+  --> $DIR/floating_point_exp.rs:9:13
    |
 LL |     let _ = (x as f32).exp() - 1.0 + 2.0;
    |             ^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `(x as f32).exp_m1()`
 
 error: (e.pow(x) - 1) can be computed more accurately
-  --> $DIR/floating_point_exp.rs:14:13
+  --> $DIR/floating_point_exp.rs:15:13
    |
 LL |     let _ = x.exp() - 1.0;
    |             ^^^^^^^^^^^^^ help: consider using: `x.exp_m1()`
 
 error: (e.pow(x) - 1) can be computed more accurately
-  --> $DIR/floating_point_exp.rs:15:13
+  --> $DIR/floating_point_exp.rs:16:13
    |
 LL |     let _ = x.exp() - 1.0 + 2.0;
    |             ^^^^^^^^^^^^^ help: consider using: `x.exp_m1()`

tests/ui/floating_point_log.fixed

@@ -1,5 +1,5 @@
 // run-rustfix
-#![allow(dead_code, clippy::double_parens)]
+#![allow(dead_code, clippy::double_parens, clippy::unnecessary_cast)]
 #![warn(clippy::suboptimal_flops, clippy::imprecise_flops)]
 
 const TWO: f32 = 2.0;

tests/ui/floating_point_log.rs

@@ -1,5 +1,5 @@
 // run-rustfix
-#![allow(dead_code, clippy::double_parens)]
+#![allow(dead_code, clippy::double_parens, clippy::unnecessary_cast)]
 #![warn(clippy::suboptimal_flops, clippy::imprecise_flops)]
 
 const TWO: f32 = 2.0;

tests/ui/floating_point_logbase.fixed

@@ -1,5 +1,6 @@
 // run-rustfix
 #![warn(clippy::suboptimal_flops)]
+#![allow(clippy::unnecessary_cast)]
 
 fn main() {
     let x = 3f32;

tests/ui/floating_point_logbase.rs

@@ -1,5 +1,6 @@
 // run-rustfix
 #![warn(clippy::suboptimal_flops)]
+#![allow(clippy::unnecessary_cast)]
 
 fn main() {
     let x = 3f32;

tests/ui/floating_point_logbase.stderr

@@ -1,31 +1,31 @@
 error: log base can be expressed more clearly
-  --> $DIR/floating_point_logbase.rs:7:13
+  --> $DIR/floating_point_logbase.rs:8:13
    |
 LL |     let _ = x.ln() / y.ln();
    |             ^^^^^^^^^^^^^^^ help: consider using: `x.log(y)`
    |
    = note: `-D clippy::suboptimal-flops` implied by `-D warnings`
 
 error: log base can be expressed more clearly
-  --> $DIR/floating_point_logbase.rs:8:13
+  --> $DIR/floating_point_logbase.rs:9:13
    |
 LL |     let _ = (x as f32).ln() / y.ln();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `(x as f32).log(y)`
 
 error: log base can be expressed more clearly
-  --> $DIR/floating_point_logbase.rs:9:13
+  --> $DIR/floating_point_logbase.rs:10:13
    |
 LL |     let _ = x.log2() / y.log2();
    |             ^^^^^^^^^^^^^^^^^^^ help: consider using: `x.log(y)`
 
 error: log base can be expressed more clearly
-  --> $DIR/floating_point_logbase.rs:10:13
+  --> $DIR/floating_point_logbase.rs:11:13
    |
 LL |     let _ = x.log10() / y.log10();
    |             ^^^^^^^^^^^^^^^^^^^^^ help: consider using: `x.log(y)`
 
 error: log base can be expressed more clearly
-  --> $DIR/floating_point_logbase.rs:11:13
+  --> $DIR/floating_point_logbase.rs:12:13
    |
 LL |     let _ = x.log(5f32) / y.log(5f32);
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `x.log(y)`

tests/ui/floating_point_powf.fixed

@@ -1,5 +1,6 @@
 // run-rustfix
 #![warn(clippy::suboptimal_flops, clippy::imprecise_flops)]
+#![allow(clippy::unnecessary_cast)]
 
 fn main() {
     let x = 3f32;

tests/ui/floating_point_powf.rs

@@ -1,5 +1,6 @@
 // run-rustfix
 #![warn(clippy::suboptimal_flops, clippy::imprecise_flops)]
+#![allow(clippy::unnecessary_cast)]
 
 fn main() {
     let x = 3f32;