gccrs: implement the TuplePattern and use it for function patterns

In order to handle the tuple pattern of: fn test ((x _) : (i32, i32)) -> i32 { x }
we need to recognize that ABI wise this function still takes a tuple as the parameter
to this function its just how we can address the "pattern" of the tuple changes.

So reall if this was C it would look like:

  void test (struct tuple_type __prameter)
  {
    return __parameter.0
  }

The code here reuses our existing pattern code so that we generate these implicit
bindings of the paramter with a field access so any time x is referenced it's really
just emplacing __parameter.0 for the field access into the struct which is a tuple.

Fixes #2847

gcc/rust/ChangeLog:

	* backend/rust-compile-fnparam.cc (CompileFnParam::visit): compile tuple patterns
	(CompileSelfParam::compile): update return type
	(CompileFnParam::create_tmp_param_var): return Bvariable not tree to stop ICE
	* backend/rust-compile-fnparam.h: update prototype
	* backend/rust-compile-pattern.cc (CompilePatternBindings::visit): implement TuplePattern
	* backend/rust-compile-pattern.h: update prototype

gcc/testsuite/ChangeLog:

	* rust/compile/issue-2847.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>

Author: philberty

gcc/rust/backend/rust-compile-fnparam.cc

@@ -68,25 +68,36 @@ CompileFnParam::visit (HIR::WildcardPattern &pattern)
   compiled_param = Backend::parameter_variable (fndecl, "_", decl_type, locus);
 }
 
+void
+CompileFnParam::visit (HIR::TuplePattern &pattern)
+{
+  compiled_param = create_tmp_param_var (decl_type);
+  CompilePatternBindings::Compile (
+    pattern, Backend::var_expression (compiled_param, locus), ctx);
+}
+
 void
 CompileFnParam::visit (HIR::StructPattern &pattern)
 {
-  tree tmp_param_var = create_tmp_param_var (decl_type);
-  CompilePatternBindings::Compile (pattern, tmp_param_var, ctx);
+  compiled_param = create_tmp_param_var (decl_type);
+  CompilePatternBindings::Compile (
+    pattern, Backend::var_expression (compiled_param, locus), ctx);
 }
 
 void
 CompileFnParam::visit (HIR::TupleStructPattern &pattern)
 {
-  tree tmp_param_var = create_tmp_param_var (decl_type);
-  CompilePatternBindings::Compile (pattern, tmp_param_var, ctx);
+  compiled_param = create_tmp_param_var (decl_type);
+  CompilePatternBindings::Compile (
+    pattern, Backend::var_expression (compiled_param, locus), ctx);
 }
 
 void
 CompileFnParam::visit (HIR::ReferencePattern &pattern)
 {
-  tree tmp_param_var = create_tmp_param_var (decl_type);
-  CompilePatternBindings::Compile (pattern, tmp_param_var, ctx);
+  compiled_param = create_tmp_param_var (decl_type);
+  CompilePatternBindings::Compile (
+    pattern, Backend::var_expression (compiled_param, locus), ctx);
 }
 
 Bvariable *
@@ -102,18 +113,16 @@ CompileSelfParam::compile (Context *ctx, tree fndecl, HIR::SelfParam &self,
   return Backend::parameter_variable (fndecl, "self", decl_type, locus);
 }
 
-tree
+Bvariable *
 CompileFnParam::create_tmp_param_var (tree decl_type)
 {
   // generate the anon param
   tree tmp_ident = create_tmp_var_name ("RSTPRM");
   std::string cpp_str_identifier = std::string (IDENTIFIER_POINTER (tmp_ident));
 
   decl_type = Backend::immutable_type (decl_type);
-  compiled_param = Backend::parameter_variable (fndecl, cpp_str_identifier,
-						decl_type, locus);
-
-  return Backend::var_expression (compiled_param, locus);
+  return Backend::parameter_variable (fndecl, cpp_str_identifier, decl_type,
+				      locus);
 }
 
 } // namespace Compile

gcc/rust/backend/rust-compile-fnparam.h

@@ -47,12 +47,12 @@ class CompileFnParam : private HIRCompileBase, protected HIR::HIRPatternVisitor
   void visit (HIR::QualifiedPathInExpression &) override {}
   void visit (HIR::RangePattern &) override {}
   void visit (HIR::SlicePattern &) override {}
-  void visit (HIR::TuplePattern &) override {}
+  void visit (HIR::TuplePattern &) override;
 
 private:
   CompileFnParam (Context *ctx, tree fndecl, tree decl_type, location_t locus);
 
-  tree create_tmp_param_var (tree decl_type);
+  Bvariable *create_tmp_param_var (tree decl_type);
 
   tree fndecl;
   tree decl_type;

gcc/rust/backend/rust-compile-pattern.cc

@@ -613,6 +613,92 @@ CompilePatternBindings::visit (HIR::IdentifierPattern &pattern)
 			       match_scrutinee_expr);
 }
 
+void
+CompilePatternBindings::visit (HIR::TuplePattern &pattern)
+{
+  rust_assert (pattern.has_tuple_pattern_items ());
+
+  // lookup the type
+  TyTy::BaseType *ty = nullptr;
+  bool ok
+    = ctx->get_tyctx ()->lookup_type (pattern.get_mappings ().get_hirid (),
+				      &ty);
+  rust_assert (ok);
+
+  switch (pattern.get_items ().get_item_type ())
+    {
+      case HIR::TuplePatternItems::ItemType::RANGED: {
+	size_t tuple_idx = 0;
+	auto &items
+	  = static_cast<HIR::TuplePatternItemsRanged &> (pattern.get_items ());
+
+	auto &items_lower = items.get_lower_patterns ();
+	auto &items_upper = items.get_upper_patterns ();
+
+	for (auto &sub : items_lower)
+	  {
+	    TyTy::BaseType *ty_sub = nullptr;
+	    HirId sub_id = sub->get_mappings ().get_hirid ();
+	    bool ok = ctx->get_tyctx ()->lookup_type (sub_id, &ty_sub);
+	    rust_assert (ok);
+
+	    tree sub_init
+	      = Backend::struct_field_expression (match_scrutinee_expr,
+						  tuple_idx, sub->get_locus ());
+
+	    CompilePatternBindings::Compile (*sub.get (), sub_init, ctx);
+	    tuple_idx++;
+	  }
+
+	rust_assert (ty->get_kind () == TyTy::TypeKind::TUPLE);
+	tuple_idx = static_cast<TyTy::TupleType &> (*ty).num_fields ()
+		    - items_upper.size ();
+
+	for (auto &sub : items_upper)
+	  {
+	    TyTy::BaseType *ty_sub = nullptr;
+	    HirId sub_id = sub->get_mappings ().get_hirid ();
+	    bool ok = ctx->get_tyctx ()->lookup_type (sub_id, &ty_sub);
+	    rust_assert (ok);
+
+	    tree sub_init
+	      = Backend::struct_field_expression (match_scrutinee_expr,
+						  tuple_idx, sub->get_locus ());
+	    CompilePatternBindings::Compile (*sub.get (), sub_init, ctx);
+	    tuple_idx++;
+	  }
+
+	return;
+      }
+      case HIR::TuplePatternItems::ItemType::MULTIPLE: {
+	size_t tuple_idx = 0;
+	auto &items = static_cast<HIR::TuplePatternItemsMultiple &> (
+	  pattern.get_items ());
+
+	for (auto &sub : items.get_patterns ())
+	  {
+	    TyTy::BaseType *ty_sub = nullptr;
+	    HirId sub_id = sub->get_mappings ().get_hirid ();
+	    bool ok = ctx->get_tyctx ()->lookup_type (sub_id, &ty_sub);
+	    rust_assert (ok);
+
+	    tree sub_init
+	      = Backend::struct_field_expression (match_scrutinee_expr,
+						  tuple_idx, sub->get_locus ());
+	    CompilePatternBindings::Compile (*sub.get (), sub_init, ctx);
+	    tuple_idx++;
+	  }
+
+	return;
+      }
+      default: {
+	rust_unreachable ();
+      }
+    }
+}
+
+//
+
 void
 CompilePatternLet::visit (HIR::IdentifierPattern &pattern)
 {

gcc/rust/backend/rust-compile-pattern.h

@@ -82,6 +82,7 @@ class CompilePatternBindings : public HIRCompileBase,
   void visit (HIR::TupleStructPattern &pattern) override;
   void visit (HIR::ReferencePattern &pattern) override;
   void visit (HIR::IdentifierPattern &) override;
+  void visit (HIR::TuplePattern &pattern) override;
 
   // Empty visit for unused Pattern HIR nodes.
   void visit (HIR::AltPattern &) override {}
@@ -90,7 +91,6 @@ class CompilePatternBindings : public HIRCompileBase,
   void visit (HIR::QualifiedPathInExpression &) override {}
   void visit (HIR::RangePattern &) override {}
   void visit (HIR::SlicePattern &) override {}
-  void visit (HIR::TuplePattern &) override {}
   void visit (HIR::WildcardPattern &) override {}
 
 protected:

gcc/testsuite/rust/compile/issue-2847.rs

@@ -0,0 +1,8 @@
+pub fn myfun1((x, _): (i32, i32)) -> i32 {
+    x
+}
+
+pub fn myfun2() -> i32 {
+    let (x, _) = (1, 2);
+    x
+}