[gcc/devel/rust/master] Fix HIR::LetStmt Dref nullptr

[Thomas Schwinge <tschwinge@gcc.gnu.org>]

https://gcc.gnu.org/g:2128789a386d098eb2068514baf3c85782c6a74e

commit 2128789a386d098eb2068514baf3c85782c6a74e
Author: Philip Herron <philip.herron@embecosm.com>
Date:   Thu Jul 7 12:11:00 2022 +0100

    Fix HIR::LetStmt Dref nullptr
    
    HIR::LetStmts can have optional specifiedtrs or patterns. This patch
    updates the copy constructors to respect this properly to avoid nullptr
    deref.

Diff:
---
 gcc/rust/hir/tree/rust-hir-stmt.h | 35 ++++++++++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/gcc/rust/hir/tree/rust-hir-stmt.h b/gcc/rust/hir/tree/rust-hir-stmt.h
index 54d3e218015..5247b0aa0f0 100644
--- a/gcc/rust/hir/tree/rust-hir-stmt.h
+++ b/gcc/rust/hir/tree/rust-hir-stmt.h
@@ -91,20 +91,41 @@ public:
   // Copy constructor with clone
   LetStmt (LetStmt const &other)
     : Stmt (other.mappings), outer_attrs (other.outer_attrs),
-      variables_pattern (other.variables_pattern->clone_pattern ()),
-      type (other.type->clone_type ()),
-      init_expr (other.init_expr->clone_expr ()), locus (other.locus)
-  {}
+      locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.variables_pattern != nullptr)
+      variables_pattern = other.variables_pattern->clone_pattern ();
+
+    // guard to prevent null dereference (always required)
+    if (other.init_expr != nullptr)
+      init_expr = other.init_expr->clone_expr ();
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+  }
 
   // Overloaded assignment operator to clone
   LetStmt &operator= (LetStmt const &other)
   {
-    variables_pattern = other.variables_pattern->clone_pattern ();
-    init_expr = other.init_expr->clone_expr ();
-    type = other.type->clone_type ();
     outer_attrs = other.outer_attrs;
     locus = other.locus;
 
+    // guard to prevent null dereference (only required if error state)
+    if (other.variables_pattern != nullptr)
+      variables_pattern = other.variables_pattern->clone_pattern ();
+    else
+      variables_pattern = nullptr;
+
+    // guard to prevent null dereference (always required)
+    if (other.init_expr != nullptr)
+      init_expr = other.init_expr->clone_expr ();
+    else
+      init_expr = nullptr;
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+    else
+      type = nullptr;
+
     return *this;
   }