Fix str_to_string wrongly unmangled macros (#16276)

Closes rust-lang/rust-clippy#16271

changelog: [`str_to_string`] fix wrongly unmangled macros

clippy_lints/src/strings.rs

@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_and_then};
 use clippy_utils::res::{MaybeDef, MaybeQPath};
-use clippy_utils::source::{snippet, snippet_with_applicability};
+use clippy_utils::source::{snippet, snippet_with_applicability, snippet_with_context};
 use clippy_utils::{
     SpanlessEq, get_expr_use_or_unification_node, get_parent_expr, is_lint_allowed, method_calls, peel_blocks, sym,
 };
@@ -404,7 +404,8 @@ impl<'tcx> LateLintPass<'tcx> for StrToString {
                 "`to_string()` called on a `&str`",
                 |diag| {
                     let mut applicability = Applicability::MachineApplicable;
-                    let snippet = snippet_with_applicability(cx, self_arg.span, "..", &mut applicability);
+                    let (snippet, _) =
+                        snippet_with_context(cx, self_arg.span, expr.span.ctxt(), "..", &mut applicability);
                     diag.span_suggestion(expr.span, "try", format!("{snippet}.to_owned()"), applicability);
                 },
             );

tests/ui/str_to_string.fixed

@@ -8,3 +8,17 @@ fn main() {
     msg.to_owned();
     //~^ str_to_string
 }
+
+fn issue16271(key: &[u8]) {
+    macro_rules! t {
+        ($e:expr) => {
+            match $e {
+                Ok(e) => e,
+                Err(e) => panic!("{} failed with {}", stringify!($e), e),
+            }
+        };
+    }
+
+    let _value = t!(str::from_utf8(key)).to_owned();
+    //~^ str_to_string
+}

tests/ui/str_to_string.rs

@@ -8,3 +8,17 @@ fn main() {
     msg.to_string();
     //~^ str_to_string
 }
+
+fn issue16271(key: &[u8]) {
+    macro_rules! t {
+        ($e:expr) => {
+            match $e {
+                Ok(e) => e,
+                Err(e) => panic!("{} failed with {}", stringify!($e), e),
+            }
+        };
+    }
+
+    let _value = t!(str::from_utf8(key)).to_string();
+    //~^ str_to_string
+}

tests/ui/str_to_string.stderr

@@ -13,5 +13,11 @@ error: `to_string()` called on a `&str`
 LL |     msg.to_string();
    |     ^^^^^^^^^^^^^^^ help: try: `msg.to_owned()`
 
-error: aborting due to 2 previous errors
+error: `to_string()` called on a `&str`
+  --> tests/ui/str_to_string.rs:22:18
+   |
+LL |     let _value = t!(str::from_utf8(key)).to_string();
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `t!(str::from_utf8(key)).to_owned()`
+
+error: aborting due to 3 previous errors