Fixed local shadowing the caller's argument issue

crates/ide-assists/src/handlers/inline_call.rs

@@ -1,3 +1,5 @@
+use std::collections::BTreeSet;
+
 use ast::make;
 use either::Either;
 use hir::{db::HirDatabase, PathResolution, Semantics, TypeInfo};
@@ -373,8 +375,44 @@ fn inline(
                 })
         }
     }
+
+    let mut func_let_vars: BTreeSet<String> = BTreeSet::new();
+
+    // grab all of the local variable declarations in the function
+    for stmt in fn_body.statements() {
+        if let Some(let_stmt) = ast::LetStmt::cast(stmt.syntax().to_owned()) {
+            for has_token in let_stmt.syntax().children_with_tokens() {
+                if let Some(node) = has_token.as_node() {
+                    if let Some(ident_pat) = ast::IdentPat::cast(node.to_owned()) {
+                        func_let_vars.insert(ident_pat.syntax().text().to_string());
+                    }
+                }
+            }
+        }
+    }
+
     // Inline parameter expressions or generate `let` statements depending on whether inlining works or not.
     for ((pat, param_ty, _), usages, expr) in izip!(params, param_use_nodes, arguments).rev() {
+        // izip confuses RA due to our lack of hygiene info currently losing us type info causing incorrect errors
+        let usages: &[ast::PathExpr] = &*usages;
+        let expr: &ast::Expr = expr;
+
+        let insert_let_stmt = || {
+            let ty = sema.type_of_expr(expr).filter(TypeInfo::has_adjustment).and(param_ty.clone());
+            if let Some(stmt_list) = body.stmt_list() {
+                stmt_list.push_front(
+                    make::let_stmt(pat.clone(), ty, Some(expr.clone())).clone_for_update().into(),
+                )
+            }
+        };
+
+        // check if there is a local var in the function that conflicts with parameter
+        // if it does then emit a let statement and continue
+        if func_let_vars.contains(&expr.syntax().text().to_string()) {
+            insert_let_stmt();
+            continue;
+        }
+
         let inline_direct = |usage, replacement: &ast::Expr| {
             if let Some(field) = path_expr_as_record_field(usage) {
                 cov_mark::hit!(inline_call_inline_direct_field);
@@ -383,9 +421,7 @@ fn inline(
                 ted::replace(usage.syntax(), &replacement.syntax().clone_for_update());
             }
         };
-        // izip confuses RA due to our lack of hygiene info currently losing us type info causing incorrect errors
-        let usages: &[ast::PathExpr] = &*usages;
-        let expr: &ast::Expr = expr;
+
         match usages {
             // inline single use closure arguments
             [usage]
@@ -408,18 +444,11 @@ fn inline(
             }
             // can't inline, emit a let statement
             _ => {
-                let ty =
-                    sema.type_of_expr(expr).filter(TypeInfo::has_adjustment).and(param_ty.clone());
-                if let Some(stmt_list) = body.stmt_list() {
-                    stmt_list.push_front(
-                        make::let_stmt(pat.clone(), ty, Some(expr.clone()))
-                            .clone_for_update()
-                            .into(),
-                    )
-                }
+                insert_let_stmt();
             }
         }
     }
+
     if let Some(generic_arg_list) = generic_arg_list.clone() {
         if let Some((target, source)) = &sema.scope(node.syntax()).zip(sema.scope(fn_body.syntax()))
         {
@@ -1256,4 +1285,37 @@ impl A {
 "#,
         )
     }
+
+    #[test]
+    fn local_variable_shadowing_callers_argument() {
+        check_assist(
+            inline_call,
+            r#"
+fn foo(bar: u32, baz: u32) -> u32 {
+    let a = 1;
+    bar * baz * a * 6
+}
+fn main() {
+    let a = 7;
+    let b = 1;
+    let res = foo$0(a, b);
+}
+"#,
+            r#"
+fn foo(bar: u32, baz: u32) -> u32 {
+    let a = 1;
+    bar * baz * a * 6
+}
+fn main() {
+    let a = 7;
+    let b = 1;
+    let res = {
+        let bar = a;
+        let a = 1;
+        bar * b * a * 6
+    };
+}
+"#,
+        );
+    }
 }