Fix invalid_upcast_comparisons wrongly unmangled macros (rust-lang#15663)

Closes rust-lang/rust-clippy#15662

changelog: [`invalid_upcast_comparisons`] fix wrong unmangle of macros

Author: samueltardieu

clippy_lints/src/invalid_upcast_comparisons.rs

@@ -1,3 +1,4 @@
+use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::layout::LayoutOf;
@@ -9,7 +10,7 @@ use clippy_utils::comparisons;
 use clippy_utils::comparisons::Rel;
 use clippy_utils::consts::{ConstEvalCtxt, FullInt};
 use clippy_utils::diagnostics::span_lint;
-use clippy_utils::source::snippet;
+use clippy_utils::source::snippet_with_context;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -69,13 +70,21 @@ fn numeric_cast_precast_bounds(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<
 
 fn err_upcast_comparison(cx: &LateContext<'_>, span: Span, expr: &Expr<'_>, always: bool) {
     if let ExprKind::Cast(cast_val, _) = expr.kind {
+        let mut applicability = Applicability::MachineApplicable;
+        let (cast_val_snip, _) = snippet_with_context(
+            cx,
+            cast_val.span,
+            expr.span.ctxt(),
+            "the expression",
+            &mut applicability,
+        );
         span_lint(
             cx,
             INVALID_UPCAST_COMPARISONS,
             span,
             format!(
                 "because of the numeric bounds on `{}` prior to casting, this expression is always {}",
-                snippet(cx, cast_val.span, "the expression"),
+                cast_val_snip,
                 if always { "true" } else { "false" },
             ),
         );

tests/ui/invalid_upcast_comparisons.rs

@@ -133,3 +133,15 @@ fn main() {
 
     -5 == (u32 as i32);
 }
+
+fn issue15662() {
+    macro_rules! add_one {
+        ($x:expr) => {
+            $x + 1
+        };
+    }
+
+    let x: u8 = 1;
+    (add_one!(x) as u32) > 300;
+    //~^ invalid_upcast_comparisons
+}

tests/ui/invalid_upcast_comparisons.stderr

@@ -163,5 +163,11 @@ error: because of the numeric bounds on `u8` prior to casting, this expression i
 LL |     -5 >= (u8 as i32);
    |     ^^^^^^^^^^^^^^^^^
 
-error: aborting due to 27 previous errors
+error: because of the numeric bounds on `add_one!(x)` prior to casting, this expression is always false
+  --> tests/ui/invalid_upcast_comparisons.rs:145:5
+   |
+LL |     (add_one!(x) as u32) > 300;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 28 previous errors