fix: useless_let_if_seq wrongly unmangled macros

Author: profetia

clippy_lints/src/let_if_seq.rs

@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::span_lint_hir_and_then;
 use clippy_utils::res::MaybeResPath;
-use clippy_utils::source::snippet;
+use clippy_utils::source::{snippet, snippet_with_context};
 use clippy_utils::visitors::is_local_used;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
@@ -117,14 +117,16 @@ fn check_block_inner<'tcx>(cx: &LateContext<'tcx>, stmt: &'tcx hir::Stmt<'tcx>,
         // FIXME: this should not suggest `mut` if we can detect that the variable is not
         // use mutably after the `if`
 
+        let mut applicability = Applicability::HasPlaceholders;
+        let (cond_snip, _) = snippet_with_context(cx, cond.span, if_.span.ctxt(), "_", &mut applicability);
+        let (value_snip, _) = snippet_with_context(cx, value.span, if_.span.ctxt(), "<value>", &mut applicability);
+        let (default_snip, _) =
+            snippet_with_context(cx, default.span, if_.span.ctxt(), "<default>", &mut applicability);
         let sug = format!(
-            "let {mutability}{name} = if {cond} {{{then} {value} }} else {{{else} {default} }};",
+            "let {mutability}{name} = if {cond_snip} {{{then} {value_snip} }} else {{{else} {default_snip} }};",
             name=ident.name,
-            cond=snippet(cx, cond.span, "_"),
             then=if then.stmts.len() > 1 { " ..;" } else { "" },
             else=if default_multi_stmts { " ..;" } else { "" },
-            value=snippet(cx, value.span, "<value>"),
-            default=snippet(cx, default.span, "<default>"),
         );
         span_lint_hir_and_then(
             cx,
@@ -133,12 +135,7 @@ fn check_block_inner<'tcx>(cx: &LateContext<'tcx>, stmt: &'tcx hir::Stmt<'tcx>,
             span,
             "`if _ { .. } else { .. }` is an expression",
             |diag| {
-                diag.span_suggestion(
-                    span,
-                    "it is more idiomatic to write",
-                    sug,
-                    Applicability::HasPlaceholders,
-                );
+                diag.span_suggestion(span, "it is more idiomatic to write", sug, applicability);
                 if !mutability.is_empty() {
                     diag.note("you might not need `mut` at all");
                 }

tests/ui/let_if_seq.rs

@@ -149,3 +149,24 @@ fn issue16062(bar: fn() -> bool) {
         foo = 0;
     }
 }
+
+fn issue16064(bar: fn() -> bool) {
+    macro_rules! mac {
+        ($e:expr) => {
+            $e()
+        };
+        ($base:expr, $lit:expr) => {
+            $lit * $base + 2
+        };
+    }
+
+    let foo;
+    //~^ useless_let_if_seq
+    if mac!(bar) {
+        foo = mac!(10, 4);
+    } else {
+        foo = 0;
+    }
+
+    let bar = 1;
+}

tests/ui/let_if_seq.stderr

@@ -64,5 +64,17 @@ LL | |         foo = 0;
 LL | |     }
    | |_____^ help: it is more idiomatic to write: `let foo = if bar() { 42 } else { 0 };`
 
-error: aborting due to 5 previous errors
+error: `if _ { .. } else { .. }` is an expression
+  --> tests/ui/let_if_seq.rs:163:5
+   |
+LL | /     let foo;
+LL | |
+LL | |     if mac!(bar) {
+LL | |         foo = mac!(10, 4);
+LL | |     } else {
+LL | |         foo = 0;
+LL | |     }
+   | |_____^ help: it is more idiomatic to write: `let foo = if mac!(bar) { mac!(10, 4) } else { 0 };`
+
+error: aborting due to 6 previous errors