keep redundant_local from running in proc macros

Author: max-niederman

clippy_lints/src/redundant_local.rs

@@ -1,7 +1,8 @@
-use clippy_utils::diagnostics::span_lint_and_help;
+use clippy_utils::{diagnostics::span_lint_and_help, source::snippet_opt};
 use rustc_ast::{
     ast::{BindingAnnotation, Block, Expr, ExprKind, LocalKind, Mutability, Pat, PatKind, Path, StmtKind},
     visit::FnKind,
+    Local,
 };
 use rustc_data_structures::fx::FxHashMap;
 use rustc_lint::{EarlyContext, EarlyLintPass};
@@ -91,6 +92,7 @@ fn check_block_with_bindings(cx: &EarlyContext<'_>, bindings: &mut FxHashMap<Ide
                 if segments.len() == 1 && segments[0].ident == ident;
                 if let Some(prev) = bindings.get(&ident);
                 if mutability == prev.mutability;
+                if is_local_user_controlled(cx, local);
                 then {
                     span_lint_and_help(
                         cx,
@@ -123,3 +125,12 @@ fn collect_introduced_bindings(bindings: &mut FxHashMap<Ident, BindingInfo>, pat
         true
     });
 }
+
+// check if a local is actually controlled by the user
+// otherwise, (macro or compiler generated), we should not lint it
+fn is_local_user_controlled(cx: &EarlyContext<'_>, local: &Local) -> bool {
+    match snippet_opt(cx, local.span) {
+        Some(snippet) => snippet.starts_with("let") && snippet.ends_with(';'),
+        None => false,
+    }
+}