Fix rust-lang#11738: allow cast lints in macros

Removed the `from_expansion` guard clause for cast lints, so that these warnings can be generated for internal macros.

Author: franciscoBSalgueiro

clippy_lints/src/casts/mod.rs

@@ -754,13 +754,10 @@ impl_lint_pass!(Casts => [
 
 impl<'tcx> LateLintPass<'tcx> for Casts {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
-        if !in_external_macro(cx.sess(), expr.span) {
-            ptr_as_ptr::check(cx, expr, &self.msrv);
-        }
-
-        if expr.span.from_expansion() {
+        if in_external_macro(cx.sess(), expr.span) {
             return;
         }
+        ptr_as_ptr::check(cx, expr, &self.msrv);
 
         if let ExprKind::Cast(cast_expr, cast_to_hir) = expr.kind {
             if is_hir_ty_cfg_dependant(cx, cast_to_hir) {
@@ -771,7 +768,7 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
                 cx.typeck_results().expr_ty(expr),
             );
 
-            if unnecessary_cast::check(cx, expr, cast_expr, cast_from, cast_to) {
+            if !expr.span.from_expansion() && unnecessary_cast::check(cx, expr, cast_expr, cast_from, cast_to) {
                 return;
             }
             cast_slice_from_raw_parts::check(cx, expr, cast_expr, cast_to, &self.msrv);
@@ -782,7 +779,7 @@ impl<'tcx> LateLintPass<'tcx> for Casts {
             fn_to_numeric_cast_with_truncation::check(cx, expr, cast_expr, cast_from, cast_to);
             zero_ptr::check(cx, expr, cast_expr, cast_to_hir);
 
-            if cast_to.is_numeric() && !in_external_macro(cx.sess(), expr.span) {
+            if cast_to.is_numeric() {
                 cast_possible_truncation::check(cx, expr, cast_expr, cast_from, cast_to, cast_to_hir.span);
                 if cast_from.is_numeric() {
                     cast_possible_wrap::check(cx, expr, cast_from, cast_to);

tests/ui/cast.rs

@@ -463,6 +463,18 @@ fn issue11642() {
     }
 }
 
+fn issue11738() {
+    macro_rules! m {
+        () => {
+            let _ = i32::MIN as u32; // cast_sign_loss
+            let _ = u32::MAX as u8; // cast_possible_truncation
+            let _ = std::f64::consts::PI as f32; // cast_possible_truncation
+            let _ = 0i8 as i32; // cast_lossless
+        };
+    }
+    m!();
+}
+
 fn issue12506() -> usize {
     let bar: Result<Option<i64>, u32> = Ok(Some(10));
     bar.unwrap().unwrap() as usize

tests/ui/cast.stderr

@@ -650,8 +650,47 @@ error: casting `i32` to `u32` may lose the sign of the value
 LL |         (a.abs() * b.pow(2) / c.abs()) as u32
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+error: casting `i32` to `u32` may lose the sign of the value
+  --> tests/ui/cast.rs:469:21
+   |
+LL |             let _ = i32::MIN as u32; // cast_sign_loss
+   |                     ^^^^^^^^^^^^^^^
+...
+LL |     m!();
+   |     ---- in this macro invocation
+   |
+   = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: casting `u32` to `u8` may truncate the value
+  --> tests/ui/cast.rs:470:21
+   |
+LL |             let _ = u32::MAX as u8; // cast_possible_truncation
+   |                     ^^^^^^^^^^^^^^
+...
+LL |     m!();
+   |     ---- in this macro invocation
+   |
+   = help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...
+   = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: ... or use `try_from` and handle the error accordingly
+   |
+LL |             let _ = u8::try_from(u32::MAX); // cast_possible_truncation
+   |                     ~~~~~~~~~~~~~~~~~~~~~~
+
+error: casting `f64` to `f32` may truncate the value
+  --> tests/ui/cast.rs:471:21
+   |
+LL |             let _ = std::f64::consts::PI as f32; // cast_possible_truncation
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL |     m!();
+   |     ---- in this macro invocation
+   |
+   = help: if this is intentional allow the lint with `#[allow(clippy::cast_possible_truncation)]` ...
+   = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
+
 error: casting `i64` to `usize` may truncate the value on targets with 32-bit wide pointers
-  --> tests/ui/cast.rs:468:5
+  --> tests/ui/cast.rs:480:5
    |
 LL |     bar.unwrap().unwrap() as usize
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -663,10 +702,10 @@ LL |     usize::try_from(bar.unwrap().unwrap())
    |
 
 error: casting `i64` to `usize` may lose the sign of the value
-  --> tests/ui/cast.rs:468:5
+  --> tests/ui/cast.rs:480:5
    |
 LL |     bar.unwrap().unwrap() as usize
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 87 previous errors
+error: aborting due to 90 previous errors