Auto merge of rust-lang#9404 - lukaslueg:issue9402, r=giraffate

Fix `suboptimal_float` not linting on `{const}.powf({const})`

There used to be an early return if the receiver was an effective const but the method was not linted, not taking into account later cases where the receiver and the arguments are both effective consts for different methods. Removed the early return.

Fixes rust-lang#9402
Fixes rust-lang#9201

changelog: Fix `suboptimal_flops`, `imprecise_flops` not linting on `{const}.powf({const})` et al

Author: bors

clippy_lints/src/floating_point_arithmetic.rs

@@ -238,23 +238,23 @@ fn get_integer_from_float_constant(value: &Constant) -> Option<i32> {
 fn check_powf(cx: &LateContext<'_>, expr: &Expr<'_>, args: &[Expr<'_>]) {
     // Check receiver
     if let Some((value, _)) = constant(cx, cx.typeck_results(), &args[0]) {
-        let method = if F32(f32_consts::E) == value || F64(f64_consts::E) == value {
-            "exp"
+        if let Some(method) = if F32(f32_consts::E) == value || F64(f64_consts::E) == value {
+            Some("exp")
         } else if F32(2.0) == value || F64(2.0) == value {
-            "exp2"
+            Some("exp2")
         } else {
-            return;
-        };
-
-        span_lint_and_sugg(
-            cx,
-            SUBOPTIMAL_FLOPS,
-            expr.span,
-            "exponent for bases 2 and e can be computed more accurately",
-            "consider using",
-            format!("{}.{}()", prepare_receiver_sugg(cx, &args[1]), method),
-            Applicability::MachineApplicable,
-        );
+            None
+        } {
+            span_lint_and_sugg(
+                cx,
+                SUBOPTIMAL_FLOPS,
+                expr.span,
+                "exponent for bases 2 and e can be computed more accurately",
+                "consider using",
+                format!("{}.{}()", prepare_receiver_sugg(cx, &args[1]), method),
+                Applicability::MachineApplicable,
+            );
+        }
     }
 
     // Check argument

tests/ui/floating_point_powf.fixed

@@ -18,6 +18,11 @@ fn main() {
     let _ = x.powi(-16_777_215);
     let _ = (x as f32).powi(-16_777_215);
     let _ = (x as f32).powi(3);
+    let _ = (1.5_f32 + 1.0).cbrt();
+    let _ = 1.5_f64.cbrt();
+    let _ = 1.5_f64.sqrt();
+    let _ = 1.5_f64.powi(3);
+
     // Cases where the lint shouldn't be applied
     let _ = x.powf(2.1);
     let _ = x.powf(-2.1);

tests/ui/floating_point_powf.rs

@@ -18,6 +18,11 @@ fn main() {
     let _ = x.powf(-16_777_215.0);
     let _ = (x as f32).powf(-16_777_215.0);
     let _ = (x as f32).powf(3.0);
+    let _ = (1.5_f32 + 1.0).powf(1.0 / 3.0);
+    let _ = 1.5_f64.powf(1.0 / 3.0);
+    let _ = 1.5_f64.powf(1.0 / 2.0);
+    let _ = 1.5_f64.powf(3.0);
+
     // Cases where the lint shouldn't be applied
     let _ = x.powf(2.1);
     let _ = x.powf(-2.1);

tests/ui/floating_point_powf.stderr

@@ -92,77 +92,101 @@ error: exponentiation with integer powers can be computed more efficiently
 LL |     let _ = (x as f32).powf(3.0);
    |             ^^^^^^^^^^^^^^^^^^^^ help: consider using: `(x as f32).powi(3)`
 
+error: cube-root of a number can be computed more accurately
+  --> $DIR/floating_point_powf.rs:21:13
+   |
+LL |     let _ = (1.5_f32 + 1.0).powf(1.0 / 3.0);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `(1.5_f32 + 1.0).cbrt()`
+
+error: cube-root of a number can be computed more accurately
+  --> $DIR/floating_point_powf.rs:22:13
+   |
+LL |     let _ = 1.5_f64.powf(1.0 / 3.0);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `1.5_f64.cbrt()`
+
+error: square-root of a number can be computed more efficiently and accurately
+  --> $DIR/floating_point_powf.rs:23:13
+   |
+LL |     let _ = 1.5_f64.powf(1.0 / 2.0);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `1.5_f64.sqrt()`
+
+error: exponentiation with integer powers can be computed more efficiently
+  --> $DIR/floating_point_powf.rs:24:13
+   |
+LL |     let _ = 1.5_f64.powf(3.0);
+   |             ^^^^^^^^^^^^^^^^^ help: consider using: `1.5_f64.powi(3)`
+
 error: exponent for bases 2 and e can be computed more accurately
-  --> $DIR/floating_point_powf.rs:28:13
+  --> $DIR/floating_point_powf.rs:33:13
    |
 LL |     let _ = 2f64.powf(x);
    |             ^^^^^^^^^^^^ help: consider using: `x.exp2()`
 
 error: exponent for bases 2 and e can be computed more accurately
-  --> $DIR/floating_point_powf.rs:29:13
+  --> $DIR/floating_point_powf.rs:34:13
    |
 LL |     let _ = 2f64.powf(3.1);
    |             ^^^^^^^^^^^^^^ help: consider using: `3.1f64.exp2()`
 
 error: exponent for bases 2 and e can be computed more accurately
-  --> $DIR/floating_point_powf.rs:30:13
+  --> $DIR/floating_point_powf.rs:35:13
    |
 LL |     let _ = 2f64.powf(-3.1);
    |             ^^^^^^^^^^^^^^^ help: consider using: `(-3.1f64).exp2()`
 
 error: exponent for bases 2 and e can be computed more accurately
-  --> $DIR/floating_point_powf.rs:31:13
+  --> $DIR/floating_point_powf.rs:36:13
    |
 LL |     let _ = std::f64::consts::E.powf(x);
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `x.exp()`
 
 error: exponent for bases 2 and e can be computed more accurately
-  --> $DIR/floating_point_powf.rs:32:13
+  --> $DIR/floating_point_powf.rs:37:13
    |
 LL |     let _ = std::f64::consts::E.powf(3.1);
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `3.1f64.exp()`
 
 error: exponent for bases 2 and e can be computed more accurately
-  --> $DIR/floating_point_powf.rs:33:13
+  --> $DIR/floating_point_powf.rs:38:13
    |
 LL |     let _ = std::f64::consts::E.powf(-3.1);
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `(-3.1f64).exp()`
 
 error: square-root of a number can be computed more efficiently and accurately
-  --> $DIR/floating_point_powf.rs:34:13
+  --> $DIR/floating_point_powf.rs:39:13
    |
 LL |     let _ = x.powf(1.0 / 2.0);
    |             ^^^^^^^^^^^^^^^^^ help: consider using: `x.sqrt()`
 
 error: cube-root of a number can be computed more accurately
-  --> $DIR/floating_point_powf.rs:35:13
+  --> $DIR/floating_point_powf.rs:40:13
    |
 LL |     let _ = x.powf(1.0 / 3.0);
    |             ^^^^^^^^^^^^^^^^^ help: consider using: `x.cbrt()`
 
 error: exponentiation with integer powers can be computed more efficiently
-  --> $DIR/floating_point_powf.rs:36:13
+  --> $DIR/floating_point_powf.rs:41:13
    |
 LL |     let _ = x.powf(3.0);
    |             ^^^^^^^^^^^ help: consider using: `x.powi(3)`
 
 error: exponentiation with integer powers can be computed more efficiently
-  --> $DIR/floating_point_powf.rs:37:13
+  --> $DIR/floating_point_powf.rs:42:13
    |
 LL |     let _ = x.powf(-2.0);
    |             ^^^^^^^^^^^^ help: consider using: `x.powi(-2)`
 
 error: exponentiation with integer powers can be computed more efficiently
-  --> $DIR/floating_point_powf.rs:38:13
+  --> $DIR/floating_point_powf.rs:43:13
    |
 LL |     let _ = x.powf(-2_147_483_648.0);
    |             ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `x.powi(-2_147_483_648)`
 
 error: exponentiation with integer powers can be computed more efficiently
-  --> $DIR/floating_point_powf.rs:39:13
+  --> $DIR/floating_point_powf.rs:44:13
    |
 LL |     let _ = x.powf(2_147_483_647.0);
    |             ^^^^^^^^^^^^^^^^^^^^^^^ help: consider using: `x.powi(2_147_483_647)`
 
-error: aborting due to 27 previous errors
+error: aborting due to 31 previous errors