Do not remove cast if it would make the expression type uncertain

Author: samueltardieu

clippy_lints/src/casts/unnecessary_cast.rs

@@ -1,6 +1,7 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::numeric_literal::NumericLiteral;
 use clippy_utils::source::{SpanRangeExt, snippet_opt};
+use clippy_utils::ty::expr_type_is_certain;
 use clippy_utils::visitors::{Visitable, for_each_expr_without_closures};
 use clippy_utils::{get_parent_expr, is_hir_ty_cfg_dependant, is_ty_alias, path_to_local};
 use rustc_ast::{LitFloatType, LitIntType, LitKind};
@@ -141,7 +142,10 @@ pub(super) fn check<'tcx>(
         }
     }
 
-    if cast_from.kind() == cast_to.kind() && !expr.span.in_external_macro(cx.sess().source_map()) {
+    if cast_from.kind() == cast_to.kind()
+        && !expr.span.in_external_macro(cx.sess().source_map())
+        && expr_type_is_certain(cx, cast_expr)
+    {
         if let Some(id) = path_to_local(cast_expr)
             && !cx.tcx.hir().span(id).eq_ctxt(cast_expr.span)
         {

tests/ui/unnecessary_cast.fixed

@@ -6,6 +6,7 @@
     clippy::no_effect,
     clippy::nonstandard_macro_braces,
     clippy::unnecessary_operation,
+    clippy::double_parens,
     nonstandard_style,
     unused
 )]
@@ -269,4 +270,24 @@ mod fixable {
         { *x }.pow(2)
         //~^ unnecessary_cast
     }
+
+    fn issue_14366(i: u32) {
+        // Do not remove the cast if it helps determining the type
+        let _ = ((1.0 / 8.0) as f64).powf(i as f64);
+
+        // But remove useless casts anyway
+        let _ = ((1.0 / 8.0) as f64).powf(i as f64);
+        //~^ unnecessary_cast
+    }
+
+    fn ambiguity() {
+        pub trait T {}
+        impl T for u32 {}
+        impl T for String {}
+        fn f(_: impl T) {}
+
+        f((1 + 2) as u32);
+        f((1 + 2u32));
+        //~^ unnecessary_cast
+    }
 }

tests/ui/unnecessary_cast.rs

@@ -6,6 +6,7 @@
     clippy::no_effect,
     clippy::nonstandard_macro_braces,
     clippy::unnecessary_operation,
+    clippy::double_parens,
     nonstandard_style,
     unused
 )]
@@ -269,4 +270,24 @@ mod fixable {
         (*x as usize).pow(2)
         //~^ unnecessary_cast
     }
+
+    fn issue_14366(i: u32) {
+        // Do not remove the cast if it helps determining the type
+        let _ = ((1.0 / 8.0) as f64).powf(i as f64);
+
+        // But remove useless casts anyway
+        let _ = (((1.0 / 8.0) as f64) as f64).powf(i as f64);
+        //~^ unnecessary_cast
+    }
+
+    fn ambiguity() {
+        pub trait T {}
+        impl T for u32 {}
+        impl T for String {}
+        fn f(_: impl T) {}
+
+        f((1 + 2) as u32);
+        f((1 + 2u32) as u32);
+        //~^ unnecessary_cast
+    }
 }

tests/ui/unnecessary_cast.stderr

@@ -1,5 +1,5 @@
 error: casting raw pointers to the same type and constness is unnecessary (`*const T` -> `*const T`)
-  --> tests/ui/unnecessary_cast.rs:19:5
+  --> tests/ui/unnecessary_cast.rs:20:5
    |
 LL |     ptr as *const T
    |     ^^^^^^^^^^^^^^^ help: try: `ptr`
@@ -8,244 +8,256 @@ LL |     ptr as *const T
    = help: to override `-D warnings` add `#[allow(clippy::unnecessary_cast)]`
 
 error: casting integer literal to `i32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:55:5
+  --> tests/ui/unnecessary_cast.rs:56:5
    |
 LL |     1i32 as i32;
    |     ^^^^^^^^^^^ help: try: `1_i32`
 
 error: casting float literal to `f32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:57:5
+  --> tests/ui/unnecessary_cast.rs:58:5
    |
 LL |     1f32 as f32;
    |     ^^^^^^^^^^^ help: try: `1_f32`
 
 error: casting to the same type is unnecessary (`bool` -> `bool`)
-  --> tests/ui/unnecessary_cast.rs:59:5
+  --> tests/ui/unnecessary_cast.rs:60:5
    |
 LL |     false as bool;
    |     ^^^^^^^^^^^^^ help: try: `false`
 
 error: casting integer literal to `i32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:63:5
+  --> tests/ui/unnecessary_cast.rs:64:5
    |
 LL |     -1_i32 as i32;
    |     ^^^^^^^^^^^^^ help: try: `-1_i32`
 
 error: casting integer literal to `i32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:65:5
+  --> tests/ui/unnecessary_cast.rs:66:5
    |
 LL |     - 1_i32 as i32;
    |     ^^^^^^^^^^^^^^ help: try: `- 1_i32`
 
 error: casting float literal to `f32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:67:5
+  --> tests/ui/unnecessary_cast.rs:68:5
    |
 LL |     -1f32 as f32;
    |     ^^^^^^^^^^^^ help: try: `-1_f32`
 
 error: casting integer literal to `i32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:69:5
+  --> tests/ui/unnecessary_cast.rs:70:5
    |
 LL |     1_i32 as i32;
    |     ^^^^^^^^^^^^ help: try: `1_i32`
 
 error: casting float literal to `f32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:71:5
+  --> tests/ui/unnecessary_cast.rs:72:5
    |
 LL |     1_f32 as f32;
    |     ^^^^^^^^^^^^ help: try: `1_f32`
 
 error: casting raw pointers to the same type and constness is unnecessary (`*const u8` -> `*const u8`)
-  --> tests/ui/unnecessary_cast.rs:74:22
+  --> tests/ui/unnecessary_cast.rs:75:22
    |
 LL |     let _: *mut u8 = [1u8, 2].as_ptr() as *const u8 as *mut u8;
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `[1u8, 2].as_ptr()`
 
 error: casting raw pointers to the same type and constness is unnecessary (`*const u8` -> `*const u8`)
-  --> tests/ui/unnecessary_cast.rs:77:5
+  --> tests/ui/unnecessary_cast.rs:78:5
    |
 LL |     [1u8, 2].as_ptr() as *const u8;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `[1u8, 2].as_ptr()`
 
 error: casting raw pointers to the same type and constness is unnecessary (`*mut u8` -> `*mut u8`)
-  --> tests/ui/unnecessary_cast.rs:80:5
+  --> tests/ui/unnecessary_cast.rs:81:5
    |
 LL |     [1u8, 2].as_mut_ptr() as *mut u8;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `[1u8, 2].as_mut_ptr()`
 
 error: casting raw pointers to the same type and constness is unnecessary (`*const u32` -> `*const u32`)
-  --> tests/ui/unnecessary_cast.rs:92:5
+  --> tests/ui/unnecessary_cast.rs:93:5
    |
 LL |     owo::<u32>([1u32].as_ptr()) as *const u32;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `owo::<u32>([1u32].as_ptr())`
 
 error: casting raw pointers to the same type and constness is unnecessary (`*const u8` -> `*const u8`)
-  --> tests/ui/unnecessary_cast.rs:94:5
+  --> tests/ui/unnecessary_cast.rs:95:5
    |
 LL |     uwu::<u32, u8>([1u32].as_ptr()) as *const u8;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `uwu::<u32, u8>([1u32].as_ptr())`
 
 error: casting raw pointers to the same type and constness is unnecessary (`*const u32` -> `*const u32`)
-  --> tests/ui/unnecessary_cast.rs:97:5
+  --> tests/ui/unnecessary_cast.rs:98:5
    |
 LL |     uwu::<u32, u32>([1u32].as_ptr()) as *const u32;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `uwu::<u32, u32>([1u32].as_ptr())`
 
 error: casting to the same type is unnecessary (`u32` -> `u32`)
-  --> tests/ui/unnecessary_cast.rs:133:5
+  --> tests/ui/unnecessary_cast.rs:134:5
    |
 LL |     aaa() as u32;
    |     ^^^^^^^^^^^^ help: try: `aaa()`
 
 error: casting to the same type is unnecessary (`u32` -> `u32`)
-  --> tests/ui/unnecessary_cast.rs:136:5
+  --> tests/ui/unnecessary_cast.rs:137:5
    |
 LL |     aaa() as u32;
    |     ^^^^^^^^^^^^ help: try: `aaa()`
 
 error: casting integer literal to `f32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:173:9
+  --> tests/ui/unnecessary_cast.rs:174:9
    |
 LL |         100 as f32;
    |         ^^^^^^^^^^ help: try: `100_f32`
 
 error: casting integer literal to `f64` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:175:9
+  --> tests/ui/unnecessary_cast.rs:176:9
    |
 LL |         100 as f64;
    |         ^^^^^^^^^^ help: try: `100_f64`
 
 error: casting integer literal to `f64` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:177:9
+  --> tests/ui/unnecessary_cast.rs:178:9
    |
 LL |         100_i32 as f64;
    |         ^^^^^^^^^^^^^^ help: try: `100_f64`
 
 error: casting integer literal to `f32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:179:17
+  --> tests/ui/unnecessary_cast.rs:180:17
    |
 LL |         let _ = -100 as f32;
    |                 ^^^^^^^^^^^ help: try: `-100_f32`
 
 error: casting integer literal to `f64` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:181:17
+  --> tests/ui/unnecessary_cast.rs:182:17
    |
 LL |         let _ = -100 as f64;
    |                 ^^^^^^^^^^^ help: try: `-100_f64`
 
 error: casting integer literal to `f64` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:183:17
+  --> tests/ui/unnecessary_cast.rs:184:17
    |
 LL |         let _ = -100_i32 as f64;
    |                 ^^^^^^^^^^^^^^^ help: try: `-100_f64`
 
 error: casting float literal to `f32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:185:9
+  --> tests/ui/unnecessary_cast.rs:186:9
    |
 LL |         100. as f32;
    |         ^^^^^^^^^^^ help: try: `100_f32`
 
 error: casting float literal to `f64` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:187:9
+  --> tests/ui/unnecessary_cast.rs:188:9
    |
 LL |         100. as f64;
    |         ^^^^^^^^^^^ help: try: `100_f64`
 
 error: casting integer literal to `u32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:200:9
+  --> tests/ui/unnecessary_cast.rs:201:9
    |
 LL |         1 as u32;
    |         ^^^^^^^^ help: try: `1_u32`
 
 error: casting integer literal to `i32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:202:9
+  --> tests/ui/unnecessary_cast.rs:203:9
    |
 LL |         0x10 as i32;
    |         ^^^^^^^^^^^ help: try: `0x10_i32`
 
 error: casting integer literal to `usize` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:204:9
+  --> tests/ui/unnecessary_cast.rs:205:9
    |
 LL |         0b10 as usize;
    |         ^^^^^^^^^^^^^ help: try: `0b10_usize`
 
 error: casting integer literal to `u16` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:206:9
+  --> tests/ui/unnecessary_cast.rs:207:9
    |
 LL |         0o73 as u16;
    |         ^^^^^^^^^^^ help: try: `0o73_u16`
 
 error: casting integer literal to `u32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:208:9
+  --> tests/ui/unnecessary_cast.rs:209:9
    |
 LL |         1_000_000_000 as u32;
    |         ^^^^^^^^^^^^^^^^^^^^ help: try: `1_000_000_000_u32`
 
 error: casting float literal to `f64` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:211:9
+  --> tests/ui/unnecessary_cast.rs:212:9
    |
 LL |         1.0 as f64;
    |         ^^^^^^^^^^ help: try: `1.0_f64`
 
 error: casting float literal to `f32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:213:9
+  --> tests/ui/unnecessary_cast.rs:214:9
    |
 LL |         0.5 as f32;
    |         ^^^^^^^^^^ help: try: `0.5_f32`
 
 error: casting integer literal to `i32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:218:17
+  --> tests/ui/unnecessary_cast.rs:219:17
    |
 LL |         let _ = -1 as i32;
    |                 ^^^^^^^^^ help: try: `-1_i32`
 
 error: casting float literal to `f32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:220:17
+  --> tests/ui/unnecessary_cast.rs:221:17
    |
 LL |         let _ = -1.0 as f32;
    |                 ^^^^^^^^^^^ help: try: `-1.0_f32`
 
 error: casting to the same type is unnecessary (`i32` -> `i32`)
-  --> tests/ui/unnecessary_cast.rs:227:18
+  --> tests/ui/unnecessary_cast.rs:228:18
    |
 LL |         let _ = &(x as i32);
    |                  ^^^^^^^^^^ help: try: `{ x }`
 
 error: casting integer literal to `i32` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:234:22
+  --> tests/ui/unnecessary_cast.rs:235:22
    |
 LL |         let _: i32 = -(1) as i32;
    |                      ^^^^^^^^^^^ help: try: `-1_i32`
 
 error: casting integer literal to `i64` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:237:22
+  --> tests/ui/unnecessary_cast.rs:238:22
    |
 LL |         let _: i64 = -(1) as i64;
    |                      ^^^^^^^^^^^ help: try: `-1_i64`
 
 error: casting float literal to `f64` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:245:22
+  --> tests/ui/unnecessary_cast.rs:246:22
    |
 LL |         let _: f64 = (-8.0 as f64).exp();
    |                      ^^^^^^^^^^^^^ help: try: `(-8.0_f64)`
 
 error: casting float literal to `f64` is unnecessary
-  --> tests/ui/unnecessary_cast.rs:248:23
+  --> tests/ui/unnecessary_cast.rs:249:23
    |
 LL |         let _: f64 = -(8.0 as f64).exp(); // should suggest `-8.0_f64.exp()` here not to change code behavior
    |                       ^^^^^^^^^^^^ help: try: `8.0_f64`
 
 error: casting to the same type is unnecessary (`f32` -> `f32`)
-  --> tests/ui/unnecessary_cast.rs:258:20
+  --> tests/ui/unnecessary_cast.rs:259:20
    |
 LL |         let _num = foo() as f32;
    |                    ^^^^^^^^^^^^ help: try: `foo()`
 
 error: casting to the same type is unnecessary (`usize` -> `usize`)
-  --> tests/ui/unnecessary_cast.rs:269:9
+  --> tests/ui/unnecessary_cast.rs:270:9
    |
 LL |         (*x as usize).pow(2)
    |         ^^^^^^^^^^^^^ help: try: `{ *x }`
 
-error: aborting due to 41 previous errors
+error: casting to the same type is unnecessary (`f64` -> `f64`)
+  --> tests/ui/unnecessary_cast.rs:279:17
+   |
+LL |         let _ = (((1.0 / 8.0) as f64) as f64).powf(i as f64);
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `((1.0 / 8.0) as f64)`
+
+error: casting to the same type is unnecessary (`u32` -> `u32`)
+  --> tests/ui/unnecessary_cast.rs:290:11
+   |
+LL |         f((1 + 2u32) as u32);
+   |           ^^^^^^^^^^^^^^^^^ help: try: `(1 + 2u32)`
+
+error: aborting due to 43 previous errors