Commit f6cbb73c74

Andrew Kelley <superjoe30@gmail.com>
2016-12-02 03:08:12
rewrite scope implementation
* now there are not extra unused hash tables * each variable declaration opens a new scope inside a function
1 parent c6ace97
src/all_types.hpp
@@ -31,6 +31,7 @@ struct ConstExprValue;
 struct IrInstruction;
 struct IrInstructionCast;
 struct IrBasicBlock;
+struct ScopeDecls;
 
 struct IrExecutable {
     ZigList<IrBasicBlock *> basic_block_list;
@@ -251,8 +252,8 @@ struct AstNodeFnDef {
 
     // populated by semantic analyzer
     TypeTableEntry *implicit_return_type;
-    // the first child block context
-    Scope *scope;
+    Scope *containing_scope;
+    Scope *child_scope;
 };
 
 struct AstNodeFnDecl {
@@ -638,7 +639,7 @@ struct AstNodeStructDecl {
     ZigList<AstNode *> decls;
 
     // populated by semantic analyzer
-    Scope *scope;
+    ScopeDecls *decls_scope;
     TypeTableEntry *type_entry;
     TypeTableEntry *generic_fn_type;
     bool skip;
@@ -884,7 +885,7 @@ struct TypeTableEntryStruct {
     uint64_t size_bytes;
     bool is_invalid; // true if any fields are invalid
     bool is_slice;
-    Scope *scope;
+    ScopeDecls *decls_scope;
 
     // set this flag temporarily to detect infinite loops
     bool embedded_in_current;
@@ -910,7 +911,7 @@ struct TypeTableEntryEnum {
     TypeTableEntry *tag_type;
     TypeTableEntry *union_type;
 
-    Scope *scope;
+    ScopeDecls *decls_scope;
 
     // set this flag temporarily to detect infinite loops
     bool embedded_in_current;
@@ -926,7 +927,7 @@ struct TypeTableEntryUnion {
     TypeStructField *fields;
     uint64_t size_bytes;
     bool is_invalid; // true if any fields are invalid
-    Scope *scope;
+    ScopeDecls *decls_scope;
 
     // set this flag temporarily to detect infinite loops
     bool embedded_in_current;
@@ -1044,7 +1045,7 @@ struct ImportTableEntry {
     ZigLLVMDIFile *di_file;
     Buf *source_code;
     ZigList<size_t> *line_offsets;
-    Scope *scope;
+    ScopeDecls *decls_scope;
     AstNode *c_import_node;
     bool any_imports_failed;
 
@@ -1070,8 +1071,6 @@ struct FnTableEntry {
     AstNode *proto_node;
     AstNode *fn_def_node;
     ImportTableEntry *import_entry;
-    // Required to be a pre-order traversal of the AST. (parents must come before children)
-    ZigList<Scope *> all_block_contexts;
     Buf symbol_name;
     TypeTableEntry *type_entry; // function type
     bool internal_linkage;
@@ -1310,7 +1309,8 @@ struct VariableTableEntry {
     ZigLLVMDILocalVariable *di_loc_var;
     size_t src_arg_index;
     size_t gen_arg_index;
-    Scope *scope;
+    Scope *parent_scope;
+    Scope *child_scope;
     LLVMValueRef param_value_ref;
     bool force_depends_on_compile_var;
     ImportTableEntry *import;
@@ -1334,26 +1334,77 @@ struct LabelTableEntry {
 struct Scope {
     AstNode *node;
 
-    // any variables that are introduced by this scope
+    // if the scope has a parent, this is it. Every scope has a parent except
+    // ScopeIdGlobal
+    Scope *parent;
+
+    ZigLLVMDIScope *di_scope;
+
+    bool safety_off;
+    AstNode *safety_set_node;
+};
+
+// This scope comes from global declarations or from
+// declarations in a container declaration
+// NodeTypeRoot, NodeTypeContainerDecl
+struct ScopeDecls {
+    Scope base;
+
+    HashMap<Buf *, AstNode *, buf_hash, buf_eql_buf> decl_table;
+};
+
+// This scope comes from a container declaration such as a struct,
+// enum, or union.
+struct ScopeContainer {
+    Scope base;
+
     HashMap<Buf *, AstNode *, buf_hash, buf_eql_buf> decl_table;
-    HashMap<Buf *, VariableTableEntry *, buf_hash, buf_eql_buf> var_table;
+};
+
+// This scope comes from a block expression in user code.
+// NodeTypeBlock
+struct ScopeBlock {
+    Scope base;
+
     HashMap<Buf *, LabelTableEntry *, buf_hash, buf_eql_buf> label_table; 
+};
 
-    // if the block is inside a function, this is the function it is in:
-    FnTableEntry *fn_entry;
+// This scope is created from every defer expression.
+// NodeTypeDefer
+struct ScopeDefer {
+    Scope base;
+};
 
-    // if the block has a parent, this is it
-    Scope *parent;
+// This scope is created for every variable declaration inside an IrExecutable
+// NodeTypeVariableDeclaration, NodeTypeParamDecl
+struct ScopeVarDecl {
+    Scope base;
 
-    // if break or continue is valid in this context, this is the loop node that
-    // it would pertain to
-    AstNode *parent_loop_node;
+    // The variable that creates this scope
+    VariableTableEntry *var;
+};
 
-    ZigLLVMDIScope *di_scope;
-    Buf *c_import_buf;
+// This scope is created for a @cImport
+// NodeTypeFnCallExpr
+struct ScopeCImport {
+    Scope base;
 
-    bool safety_off;
-    AstNode *safety_set_node;
+    Buf c_import_buf;
+};
+
+// This scope is created for a loop such as for or while in order to
+// make break and continue statements work.
+// NodeTypeForExpr or NodeTypeWhileExpr
+struct ScopeLoop {
+    Scope base;
+};
+
+// This scope is created for a function definition.
+// NodeTypeFnDef
+struct ScopeFnBody {
+    Scope base;
+
+    FnTableEntry *fn_entry;
 };
 
 enum AtomicOrder {
src/analyze.cpp
@@ -115,26 +115,24 @@ TypeTableEntry *new_type_table_entry(TypeTableEntryId id) {
     return entry;
 }
 
-static Scope **get_container_block_context_ptr(TypeTableEntry *type_entry) {
+static ScopeDecls **get_container_scope_ptr(TypeTableEntry *type_entry) {
     if (type_entry->id == TypeTableEntryIdStruct) {
-        return &type_entry->data.structure.scope;
+        return &type_entry->data.structure.decls_scope;
     } else if (type_entry->id == TypeTableEntryIdEnum) {
-        return &type_entry->data.enumeration.scope;
+        return &type_entry->data.enumeration.decls_scope;
     } else if (type_entry->id == TypeTableEntryIdUnion) {
-        return &type_entry->data.unionation.scope;
+        return &type_entry->data.unionation.decls_scope;
     }
     zig_unreachable();
 }
 
-Scope *get_container_block_context(TypeTableEntry *type_entry) {
-    return *get_container_block_context_ptr(type_entry);
+ScopeDecls *get_container_scope(TypeTableEntry *type_entry) {
+    return *get_container_scope_ptr(type_entry);
 }
 
-static TypeTableEntry *new_container_type_entry(TypeTableEntryId id, AstNode *source_node,
-        Scope *parent_context)
-{
+static TypeTableEntry *new_container_type_entry(TypeTableEntryId id, AstNode *source_node, Scope *parent_scope) {
     TypeTableEntry *entry = new_type_table_entry(id);
-    *get_container_block_context_ptr(entry) = new_scope(source_node, parent_context);
+    *get_container_scope_ptr(entry) = create_decls_scope(source_node, parent_scope);
     return entry;
 }
 
@@ -766,11 +764,11 @@ static TypeTableEntryId container_to_type(ContainerKind kind) {
     zig_unreachable();
 }
 
-TypeTableEntry *get_partial_container_type(CodeGen *g, ImportTableEntry *import, Scope *context,
+TypeTableEntry *get_partial_container_type(CodeGen *g, ImportTableEntry *import, Scope *scope,
         ContainerKind kind, AstNode *decl_node, const char *name)
 {
     TypeTableEntryId type_id = container_to_type(kind);
-    TypeTableEntry *entry = new_container_type_entry(type_id, decl_node, context);
+    TypeTableEntry *entry = new_container_type_entry(type_id, decl_node, scope);
 
     switch (kind) {
         case ContainerKindStruct:
@@ -844,10 +842,10 @@ static IrInstruction *analyze_const_value(CodeGen *g, Scope *scope, AstNode *nod
     return result;
 }
 
-static TypeTableEntry *analyze_type_expr(CodeGen *g, ImportTableEntry *import, Scope *context,
+static TypeTableEntry *analyze_type_expr(CodeGen *g, ImportTableEntry *import, Scope *scope,
         AstNode *node)
 {
-    IrInstruction *result = analyze_const_value(g, context, node, g->builtin_types.entry_type);
+    IrInstruction *result = analyze_const_value(g, scope, node, g->builtin_types.entry_type);
     if (result->type_entry->id == TypeTableEntryIdInvalid)
         return g->builtin_types.entry_invalid;
 
@@ -861,7 +859,7 @@ static bool fn_wants_full_static_eval(FnTableEntry *fn_table_entry) {
 }
 
 // fn_table_entry is populated if and only if there is a function definition for this prototype
-static TypeTableEntry *analyze_fn_proto_type(CodeGen *g, ImportTableEntry *import, Scope *context,
+static TypeTableEntry *analyze_fn_proto_type(CodeGen *g, ImportTableEntry *import, Scope *scope,
         TypeTableEntry *expected_type, AstNode *node, bool is_naked, bool is_cold, FnTableEntry *fn_table_entry)
 {
     assert(node->type == NodeTypeFnProto);
@@ -888,7 +886,7 @@ static TypeTableEntry *analyze_fn_proto_type(CodeGen *g, ImportTableEntry *impor
         if (fn_proto->skip) {
             type_entry = g->builtin_types.entry_invalid;
         } else {
-            type_entry = analyze_type_expr(g, import, context, child->data.param_decl.type);
+            type_entry = analyze_type_expr(g, import, scope, child->data.param_decl.type);
         }
 
         switch (type_entry->id) {
@@ -951,7 +949,7 @@ static TypeTableEntry *analyze_fn_proto_type(CodeGen *g, ImportTableEntry *impor
     if (fn_proto->skip) {
         fn_type_id.return_type = g->builtin_types.entry_invalid;
     } else {
-        fn_type_id.return_type = analyze_type_expr(g, import, context, fn_proto->return_type);
+        fn_type_id.return_type = analyze_type_expr(g, import, scope, fn_proto->return_type);
     }
     switch (fn_type_id.return_type->id) {
         case TypeTableEntryIdInvalid:
@@ -1022,7 +1020,7 @@ static TypeTableEntry *analyze_fn_proto_type(CodeGen *g, ImportTableEntry *impor
 }
 
 static void resolve_function_proto(CodeGen *g, AstNode *node, FnTableEntry *fn_table_entry,
-        ImportTableEntry *import, Scope *containing_context)
+        ImportTableEntry *import, Scope *containing_scope)
 {
     assert(node->type == NodeTypeFnProto);
     AstNodeFnProto *fn_proto = &node->data.fn_proto;
@@ -1037,7 +1035,7 @@ static void resolve_function_proto(CodeGen *g, AstNode *node, FnTableEntry *fn_t
 
 
 
-    TypeTableEntry *fn_type = analyze_fn_proto_type(g, import, containing_context, nullptr, node,
+    TypeTableEntry *fn_type = analyze_fn_proto_type(g, import, containing_scope, nullptr, node,
             fn_proto->is_nakedcc, fn_proto->is_coldcc, fn_table_entry);
 
     fn_table_entry->type_entry = fn_type;
@@ -1060,8 +1058,8 @@ static void resolve_function_proto(CodeGen *g, AstNode *node, FnTableEntry *fn_t
     }
 
     if (fn_table_entry->fn_def_node) {
-        Scope *context = new_scope(fn_table_entry->fn_def_node, containing_context);
-        fn_table_entry->fn_def_node->data.fn_def.scope = context;
+        fn_table_entry->fn_def_node->data.fn_def.containing_scope = create_fndef_scope(
+            fn_table_entry->fn_def_node, containing_scope, fn_table_entry);
     }
 
     if (!fn_wants_full_static_eval(fn_table_entry)) {
@@ -1095,23 +1093,6 @@ static void resolve_function_proto(CodeGen *g, AstNode *node, FnTableEntry *fn_t
             ZigLLVMAddFunctionAttr(fn_table_entry->fn_value, "no-frame-pointer-elim", "true");
             ZigLLVMAddFunctionAttr(fn_table_entry->fn_value, "no-frame-pointer-elim-non-leaf", nullptr);
         }
-
-        if (fn_table_entry->fn_def_node) {
-            // Add debug info.
-            unsigned line_number = node->line + 1;
-            unsigned scope_line = line_number;
-            bool is_definition = fn_table_entry->fn_def_node != nullptr;
-            unsigned flags = 0;
-            bool is_optimized = g->is_release_build;
-            ZigLLVMDISubprogram *subprogram = ZigLLVMCreateFunction(g->dbuilder,
-                containing_context->di_scope, buf_ptr(&fn_table_entry->symbol_name), "",
-                import->di_file, line_number,
-                fn_type->di_type, fn_table_entry->internal_linkage,
-                is_definition, scope_line, flags, is_optimized, nullptr);
-
-            fn_table_entry->fn_def_node->data.fn_def.scope->di_scope = ZigLLVMSubprogramToScope(subprogram);
-            ZigLLVMFnSetSubprogram(fn_table_entry->fn_value, subprogram);
-        }
     }
 }
 
@@ -1151,7 +1132,7 @@ static void resolve_enum_type(CodeGen *g, ImportTableEntry *import, TypeTableEnt
     uint64_t biggest_align_in_bits = 0;
     uint64_t biggest_union_member_size_in_bits = 0;
 
-    Scope *context = enum_type->data.enumeration.scope;
+    Scope *scope = &enum_type->data.enumeration.decls_scope->base;
 
     // set temporary flag
     enum_type->data.enumeration.embedded_in_current = true;
@@ -1161,7 +1142,7 @@ static void resolve_enum_type(CodeGen *g, ImportTableEntry *import, TypeTableEnt
         AstNode *field_node = decl_node->data.struct_decl.fields.at(i);
         TypeEnumField *type_enum_field = &enum_type->data.enumeration.fields[i];
         type_enum_field->name = field_node->data.struct_field.name;
-        TypeTableEntry *field_type = analyze_type_expr(g, import, context,
+        TypeTableEntry *field_type = analyze_type_expr(g, import, scope,
                 field_node->data.struct_field.type);
         type_enum_field->type_entry = field_type;
         type_enum_field->value = i;
@@ -1337,14 +1318,14 @@ static void resolve_struct_type(CodeGen *g, ImportTableEntry *import, TypeTableE
     // this field should be set to true only during the recursive calls to resolve_struct_type
     struct_type->data.structure.embedded_in_current = true;
 
-    Scope *context = struct_type->data.structure.scope;
+    Scope *scope = &struct_type->data.structure.decls_scope->base;
 
     size_t gen_field_index = 0;
     for (size_t i = 0; i < field_count; i += 1) {
         AstNode *field_node = decl_node->data.struct_decl.fields.at(i);
         TypeStructField *type_struct_field = &struct_type->data.structure.fields[i];
         type_struct_field->name = field_node->data.struct_field.name;
-        TypeTableEntry *field_type = analyze_type_expr(g, import, context,
+        TypeTableEntry *field_type = analyze_type_expr(g, import, scope,
                 field_node->data.struct_field.type);
         type_struct_field->type_entry = field_type;
         type_struct_field->src_index = i;
@@ -1463,7 +1444,7 @@ static bool get_is_generic_fn(AstNode *proto_node) {
 }
 
 static void preview_fn_proto_instance(CodeGen *g, ImportTableEntry *import, AstNode *proto_node,
-        Scope *containing_context)
+        Scope *containing_scope)
 {
     assert(proto_node->type == NodeTypeFnProto);
 
@@ -1515,7 +1496,7 @@ static void preview_fn_proto_instance(CodeGen *g, ImportTableEntry *import, AstN
 
 
     } else {
-        resolve_function_proto(g, proto_node, fn_table_entry, import, containing_context);
+        resolve_function_proto(g, proto_node, fn_table_entry, import, containing_scope);
 
         if (!fn_wants_full_static_eval(fn_table_entry)) {
             g->fn_protos.append(fn_table_entry);
@@ -1546,7 +1527,7 @@ static void preview_fn_proto_instance(CodeGen *g, ImportTableEntry *import, AstN
     }
 }
 
-static void add_top_level_decl(CodeGen *g, ImportTableEntry *import, Scope *scope,
+static void add_top_level_decl(CodeGen *g, ImportTableEntry *import, ScopeDecls *decls_scope,
         AstNode *node, Buf *name)
 {
     assert(import);
@@ -1562,19 +1543,17 @@ static void add_top_level_decl(CodeGen *g, ImportTableEntry *import, Scope *scop
         g->resolve_queue.append(node);
     }
 
-    node->scope = scope;
+    node->scope = &decls_scope->base;
 
-    auto entry = scope->decl_table.maybe_get(name);
+    auto entry = decls_scope->decl_table.put_unique(name, node);
     if (entry) {
         AstNode *other_decl_node = entry->value;
         ErrorMsg *msg = add_node_error(g, node, buf_sprintf("redefinition of '%s'", buf_ptr(name)));
         add_error_note(g, msg, other_decl_node, buf_sprintf("previous definition is here"));
-    } else {
-        scope->decl_table.put(name, node);
     }
 }
 
-static void scan_struct_decl(CodeGen *g, ImportTableEntry *import, Scope *context, AstNode *node) {
+static void scan_struct_decl(CodeGen *g, ImportTableEntry *import, ScopeDecls *decls_scope, AstNode *node) {
     assert(node->type == NodeTypeContainerDecl);
 
     if (node->data.struct_decl.type_entry) {
@@ -1583,7 +1562,7 @@ static void scan_struct_decl(CodeGen *g, ImportTableEntry *import, Scope *contex
     }
 
     Buf *name = node->data.struct_decl.name;
-    TypeTableEntry *container_type = get_partial_container_type(g, import, context,
+    TypeTableEntry *container_type = get_partial_container_type(g, import, &decls_scope->base,
             node->data.struct_decl.kind, node, buf_ptr(name));
     node->data.struct_decl.type_entry = container_type;
 
@@ -1591,8 +1570,8 @@ static void scan_struct_decl(CodeGen *g, ImportTableEntry *import, Scope *contex
     for (size_t i = 0; i < node->data.struct_decl.decls.length; i += 1) {
         AstNode *child_node = node->data.struct_decl.decls.at(i);
         get_as_top_level_decl(child_node)->parent_decl = node;
-        Scope *child_context = get_container_block_context(container_type);
-        scan_decls(g, import, child_context, child_node);
+        ScopeDecls *child_scope = get_container_scope(container_type);
+        scan_decls(g, import, child_scope, child_node);
     }
 }
 
@@ -1644,37 +1623,37 @@ static void preview_error_value_decl(CodeGen *g, AstNode *node) {
     node->data.error_value_decl.top_level_decl.resolution = TldResolutionOk;
 }
 
-void scan_decls(CodeGen *g, ImportTableEntry *import, Scope *context, AstNode *node) {
+void scan_decls(CodeGen *g, ImportTableEntry *import, ScopeDecls *decls_scope, AstNode *node) {
     switch (node->type) {
         case NodeTypeRoot:
             for (size_t i = 0; i < import->root->data.root.top_level_decls.length; i += 1) {
                 AstNode *child = import->root->data.root.top_level_decls.at(i);
-                scan_decls(g, import, context, child);
+                scan_decls(g, import, decls_scope, child);
             }
             break;
         case NodeTypeContainerDecl:
             {
                 Buf *name = node->data.struct_decl.name;
-                add_top_level_decl(g, import, context, node, name);
+                add_top_level_decl(g, import, decls_scope, node, name);
                 if (node->data.struct_decl.generic_params.length == 0) {
-                    scan_struct_decl(g, import, context, node);
+                    scan_struct_decl(g, import, decls_scope, node);
                 }
             }
             break;
         case NodeTypeFnDef:
             node->data.fn_def.fn_proto->data.fn_proto.fn_def_node = node;
-            scan_decls(g, import, context, node->data.fn_def.fn_proto);
+            scan_decls(g, import, decls_scope, node->data.fn_def.fn_proto);
             break;
         case NodeTypeVariableDeclaration:
             {
                 Buf *name = node->data.variable_declaration.symbol;
-                add_top_level_decl(g, import, context, node, name);
+                add_top_level_decl(g, import, decls_scope, node, name);
                 break;
             }
         case NodeTypeTypeDecl:
             {
                 Buf *name = node->data.type_decl.symbol;
-                add_top_level_decl(g, import, context, node, name);
+                add_top_level_decl(g, import, decls_scope, node, name);
                 break;
             }
         case NodeTypeFnProto:
@@ -1688,14 +1667,14 @@ void scan_decls(CodeGen *g, ImportTableEntry *import, Scope *context, AstNode *n
                 }
                 count_inline_and_var_args(node);
 
-                add_top_level_decl(g, import, context, node, fn_name);
+                add_top_level_decl(g, import, decls_scope, node, fn_name);
                 break;
             }
         case NodeTypeUse:
             {
                 TopLevelDecl *tld = get_as_top_level_decl(node);
                 tld->import = import;
-                node->scope = context;
+                node->scope = &decls_scope->base;
                 g->use_queue.append(node);
                 tld->import->use_decls.append(node);
                 break;
@@ -1816,70 +1795,65 @@ TypeTableEntry *validate_var_type(CodeGen *g, AstNode *source_node, TypeTableEnt
 
 // Set name to nullptr to make the variable anonymous (not visible to programmer).
 // TODO merge with definition of add_local_var in ir.cpp
-static VariableTableEntry *add_local_var_shadowable(CodeGen *g, AstNode *source_node, ImportTableEntry *import,
-        Scope *context, Buf *name, TypeTableEntry *type_entry, bool is_const, AstNode *val_node,
-        bool shadowable)
+static VariableTableEntry *add_local_var(CodeGen *g, AstNode *source_node, ImportTableEntry *import,
+        Scope *parent_scope, Buf *name, TypeTableEntry *type_entry, bool is_const, AstNode *val_node)
 {
     VariableTableEntry *variable_entry = allocate<VariableTableEntry>(1);
     variable_entry->type = type_entry;
-    variable_entry->scope = context;
+    variable_entry->parent_scope = parent_scope;
     variable_entry->import = import;
-    variable_entry->shadowable = shadowable;
+    variable_entry->shadowable = false;
     variable_entry->mem_slot_index = SIZE_MAX;
 
-    if (name) {
-        buf_init_from_buf(&variable_entry->name, name);
+    assert(name);
 
-        if (type_entry->id != TypeTableEntryIdInvalid) {
-            VariableTableEntry *existing_var = find_variable(g, context, name);
-            if (existing_var && !existing_var->shadowable) {
-                ErrorMsg *msg = add_node_error(g, source_node,
-                        buf_sprintf("redeclaration of variable '%s'", buf_ptr(name)));
-                add_error_note(g, msg, existing_var->decl_node, buf_sprintf("previous declaration is here"));
+    buf_init_from_buf(&variable_entry->name, name);
+
+    if (type_entry->id != TypeTableEntryIdInvalid) {
+        VariableTableEntry *existing_var = find_variable(g, parent_scope, name);
+        if (existing_var && !existing_var->shadowable) {
+            ErrorMsg *msg = add_node_error(g, source_node,
+                    buf_sprintf("redeclaration of variable '%s'", buf_ptr(name)));
+            add_error_note(g, msg, existing_var->decl_node, buf_sprintf("previous declaration is here"));
+            variable_entry->type = g->builtin_types.entry_invalid;
+        } else {
+            auto primitive_table_entry = g->primitive_type_table.maybe_get(name);
+            if (primitive_table_entry) {
+                TypeTableEntry *type = primitive_table_entry->value;
+                add_node_error(g, source_node,
+                        buf_sprintf("variable shadows type '%s'", buf_ptr(&type->name)));
                 variable_entry->type = g->builtin_types.entry_invalid;
             } else {
-                auto primitive_table_entry = g->primitive_type_table.maybe_get(name);
-                if (primitive_table_entry) {
-                    TypeTableEntry *type = primitive_table_entry->value;
-                    add_node_error(g, source_node,
-                            buf_sprintf("variable shadows type '%s'", buf_ptr(&type->name)));
+                AstNode *decl_node = find_decl(parent_scope, name);
+                if (decl_node && decl_node->type != NodeTypeVariableDeclaration) {
+                    ErrorMsg *msg = add_node_error(g, source_node,
+                            buf_sprintf("redefinition of '%s'", buf_ptr(name)));
+                    add_error_note(g, msg, decl_node, buf_sprintf("previous definition is here"));
                     variable_entry->type = g->builtin_types.entry_invalid;
-                } else {
-                    AstNode *decl_node = find_decl(context, name);
-                    if (decl_node && decl_node->type != NodeTypeVariableDeclaration) {
-                        ErrorMsg *msg = add_node_error(g, source_node,
-                                buf_sprintf("redefinition of '%s'", buf_ptr(name)));
-                        add_error_note(g, msg, decl_node, buf_sprintf("previous definition is here"));
-                        variable_entry->type = g->builtin_types.entry_invalid;
-                    }
                 }
             }
         }
+    }
 
-        context->var_table.put(&variable_entry->name, variable_entry);
+    Scope *child_scope;
+    if (source_node->type == NodeTypeParamDecl) {
+        child_scope = create_var_scope(source_node, parent_scope, variable_entry);
     } else {
-        // TODO replace _anon with @anon and make sure all tests still pass
-        buf_init_from_str(&variable_entry->name, "_anon");
-    }
-    if (context->fn_entry) {
-        context->fn_entry->variable_list.append(variable_entry);
+        // it's already in the decls table
+        child_scope = parent_scope;
     }
 
+
     variable_entry->src_is_const = is_const;
     variable_entry->gen_is_const = is_const;
     variable_entry->decl_node = source_node;
     variable_entry->val_node = val_node;
+    variable_entry->child_scope = child_scope;
 
 
     return variable_entry;
 }
 
-static VariableTableEntry *add_local_var(CodeGen *g, AstNode *source_node, ImportTableEntry *import,
-        Scope *context, Buf *name, TypeTableEntry *type_entry, bool is_const, AstNode *val_node)
-{
-    return add_local_var_shadowable(g, source_node, import, context, name, type_entry, is_const, val_node, false);
-}
-
 static void resolve_var_decl(CodeGen *g, ImportTableEntry *import, AstNode *node) {
     assert(node->type == NodeTypeVariableDeclaration);
 
@@ -1889,8 +1863,6 @@ static void resolve_var_decl(CodeGen *g, ImportTableEntry *import, AstNode *node
     bool is_export = (var_decl->top_level_decl.visib_mod == VisibModExport);
     bool is_extern = var_decl->is_extern;
 
-    assert(!scope->fn_entry);
-
     TypeTableEntry *explicit_type = nullptr;
     if (var_decl->type) {
         TypeTableEntry *proposed_type = analyze_type_expr(g, import, scope, var_decl->type);
@@ -1980,7 +1952,7 @@ void resolve_top_level_decl(CodeGen *g, AstNode *node, bool pointer_only) {
                 if (node->data.type_decl.override_type) {
                     entry = node->data.type_decl.override_type;
                 } else {
-                    TypeTableEntry *child_type = analyze_type_expr(g, import, import->scope, type_node);
+                    TypeTableEntry *child_type = analyze_type_expr(g, import, &import->decls_scope->base, type_node);
                     if (child_type->id == TypeTableEntryIdInvalid) {
                         entry = child_type;
                     } else {
@@ -2170,52 +2142,105 @@ bool types_match_const_cast_only(TypeTableEntry *expected_type, TypeTableEntry *
     return false;
 }
 
-Scope *new_scope(AstNode *node, Scope *parent) {
-    Scope *context = allocate<Scope>(1);
-    context->node = node;
-    context->parent = parent;
-    context->decl_table.init(1);
-    context->var_table.init(1);
-    context->label_table.init(1);
+ScopeDecls *create_decls_scope(AstNode *node, Scope *parent) {
+    assert(node->type == NodeTypeRoot || node->type == NodeTypeContainerDecl);
+    ScopeDecls *scope = allocate<ScopeDecls>(1);
+    scope->base.node = node;
+    scope->base.parent = parent;
+    scope->decl_table.init(4);
+    return scope;
+}
+
+Scope *create_block_scope(AstNode *node, Scope *parent) {
+    assert(node->type == NodeTypeBlock);
+    ScopeBlock *scope = allocate<ScopeBlock>(1);
+    scope->base.node = node;
+    scope->base.parent = parent;
+    scope->label_table.init(1);
+    return &scope->base;
+}
 
-    if (parent) {
-        context->parent_loop_node = parent->parent_loop_node;
-        context->c_import_buf = parent->c_import_buf;
-    }
+Scope *create_defer_scope(AstNode *node, Scope *parent) {
+    assert(node->type == NodeTypeDefer);
+    ScopeDefer *scope = allocate<ScopeDefer>(1);
+    scope->base.node = node;
+    scope->base.parent = parent;
+    return &scope->base;
+}
 
-    if (node && node->type == NodeTypeFnDef) {
-        AstNode *fn_proto_node = node->data.fn_def.fn_proto;
-        context->fn_entry = fn_proto_node->data.fn_proto.fn_table_entry;
-    } else if (parent) {
-        context->fn_entry = parent->fn_entry;
-    }
+Scope *create_var_scope(AstNode *node, Scope *parent, VariableTableEntry *var) {
+    assert(node->type == NodeTypeVariableDeclaration || node->type == NodeTypeParamDecl);
+    ScopeVarDecl *scope = allocate<ScopeVarDecl>(1);
+    scope->base.node = node;
+    scope->base.parent = parent;
+    scope->var = var;
+    return &scope->base;
+}
 
-    if (context->fn_entry) {
-        context->fn_entry->all_block_contexts.append(context);
-    }
+Scope *create_cimport_scope(AstNode *node, Scope *parent) {
+    assert(node->type == NodeTypeFnCallExpr);
+    ScopeCImport *scope = allocate<ScopeCImport>(1);
+    scope->base.node = node;
+    scope->base.parent = parent;
+    buf_resize(&scope->c_import_buf, 0);
+    return &scope->base;
+}
+
+Scope *create_loop_scope(AstNode *node, Scope *parent) {
+    assert(node->type == NodeTypeWhileExpr || node->type == NodeTypeForExpr);
+    ScopeLoop *scope = allocate<ScopeLoop>(1);
+    scope->base.node = node;
+    scope->base.parent = parent;
+    return &scope->base;
+}
 
-    return context;
+Scope *create_fndef_scope(AstNode *node, Scope *parent, FnTableEntry *fn_entry) {
+    assert(node->type == NodeTypeFnDef);
+    ScopeFnBody *scope = allocate<ScopeFnBody>(1);
+    scope->base.node = node;
+    scope->base.parent = parent;
+    scope->fn_entry = fn_entry;
+    return &scope->base;
 }
 
-AstNode *find_decl(Scope *context, Buf *name) {
-    while (context) {
-        auto entry = context->decl_table.maybe_get(name);
-        if (entry) {
-            return entry->value;
+AstNode *find_decl(Scope *scope, Buf *name) {
+    while (scope) {
+        if (scope->node->type == NodeTypeRoot ||
+            scope->node->type == NodeTypeContainerDecl)
+        {
+            ScopeDecls *decls_scope = (ScopeDecls *)scope;
+            auto entry = decls_scope->decl_table.maybe_get(name);
+            if (entry)
+                return entry->value;
         }
-        context = context->parent;
+        scope = scope->parent;
     }
     return nullptr;
 }
 
-VariableTableEntry *find_variable(CodeGen *g, Scope *orig_context, Buf *name) {
-    Scope *context = orig_context;
-    while (context) {
-        auto entry = context->var_table.maybe_get(name);
-        if (entry) {
-            return entry->value;
+VariableTableEntry *find_variable(CodeGen *g, Scope *scope, Buf *name) {
+    while (scope) {
+        if (scope->node->type == NodeTypeVariableDeclaration ||
+            scope->node->type == NodeTypeParamDecl)
+        {
+            ScopeVarDecl *var_scope = (ScopeVarDecl *)scope;
+            if (buf_eql_buf(name, &var_scope->var->name))
+                return var_scope->var;
+        } else if (scope->node->type == NodeTypeRoot ||
+                   scope->node->type == NodeTypeContainerDecl)
+        {
+            ScopeDecls *decls_scope = (ScopeDecls *)scope;
+            auto entry = decls_scope->decl_table.maybe_get(name);
+            if (entry) {
+                AstNode *decl_node = entry->value;
+                if (decl_node->type == NodeTypeVariableDeclaration) {
+                    VariableTableEntry *var = decl_node->data.variable_declaration.variable;
+                    if (var)
+                        return var;
+                }
+            }
         }
-        context = context->parent;
+        scope = scope->parent;
     }
 
     return nullptr;
@@ -2355,7 +2380,7 @@ static void analyze_fn_body(CodeGen *g, FnTableEntry *fn_table_entry) {
     }
     fn_table_entry->anal_state = FnAnalStateProbing;
 
-    Scope *context = node->data.fn_def.scope;
+    Scope *child_scope = node->data.fn_def.containing_scope;
 
     TypeTableEntry *fn_type = fn_table_entry->type_entry;
     FnTypeId *fn_type_id = &fn_type->data.fn.fn_type_id;
@@ -2381,16 +2406,20 @@ static void analyze_fn_body(CodeGen *g, FnTableEntry *fn_table_entry) {
             add_node_error(g, param_decl_node, buf_sprintf("missing parameter name"));
         }
 
-        VariableTableEntry *var = add_local_var(g, param_decl_node, import, context, param_decl->name,
+        VariableTableEntry *var = add_local_var(g, param_decl_node, import, child_scope, param_decl->name,
                 type, true, nullptr);
         var->src_arg_index = i;
         param_decl_node->data.param_decl.variable = var;
+        child_scope = var->child_scope;
+        fn_table_entry->variable_list.append(var);
 
         if (fn_type->data.fn.gen_param_info) {
             var->gen_arg_index = fn_type->data.fn.gen_param_info[i].gen_index;
         }
     }
 
+    node->data.fn_def.child_scope = child_scope;
+
     TypeTableEntry *expected_type = fn_type->data.fn.fn_type_id.return_type;
 
     if (fn_type->data.fn.fn_type_id.is_extern && handle_is_ptr(expected_type)) {
@@ -2456,7 +2485,7 @@ static void add_symbols_from_import(CodeGen *g, AstNode *src_use_node, AstNode *
             continue;
         }
         if (target_tld->visib_mod != VisibModPrivate) {
-            auto existing_entry = tld->import->scope->decl_table.maybe_get(target_tld->name);
+            auto existing_entry = tld->import->decls_scope->decl_table.put_unique(target_tld->name, decl_node);
             if (existing_entry) {
                 AstNode *existing_decl = existing_entry->value;
                 if (existing_decl != decl_node) {
@@ -2466,8 +2495,6 @@ static void add_symbols_from_import(CodeGen *g, AstNode *src_use_node, AstNode *
                     add_error_note(g, msg, existing_decl, buf_sprintf("previous definition here"));
                     add_error_note(g, msg, decl_node, buf_sprintf("imported definition here"));
                 }
-            } else {
-                tld->import->scope->decl_table.put(target_tld->name, decl_node);
             }
         }
     }
@@ -2494,7 +2521,7 @@ void preview_use_decl(CodeGen *g, AstNode *node) {
     assert(node->type == NodeTypeUse);
     TopLevelDecl *tld = get_as_top_level_decl(node);
 
-    IrInstruction *result = analyze_const_value(g, tld->import->scope, node->data.use.expr,
+    IrInstruction *result = analyze_const_value(g, &tld->import->decls_scope->base, node->data.use.expr,
             g->builtin_types.entry_namespace);
     if (result->type_entry->id == TypeTableEntryIdInvalid)
         tld->import->any_imports_failed = true;
@@ -2553,8 +2580,7 @@ ImportTableEntry *add_source_file(CodeGen *g, PackageTableEntry *package,
     g->import_table.put(abs_full_path, import_entry);
     g->import_queue.append(import_entry);
 
-    import_entry->scope = new_scope(import_entry->root, nullptr);
-    import_entry->scope->di_scope = ZigLLVMFileToScope(import_entry->di_file);
+    import_entry->decls_scope = create_decls_scope(import_entry->root, nullptr);
 
 
     assert(import_entry->root->type == NodeTypeRoot);
@@ -2581,7 +2607,7 @@ ImportTableEntry *add_source_file(CodeGen *g, PackageTableEntry *package,
 void semantic_analyze(CodeGen *g) {
     for (; g->import_queue_index < g->import_queue.length; g->import_queue_index += 1) {
         ImportTableEntry *import = g->import_queue.at(g->import_queue_index);
-        scan_decls(g, import, import->scope, import->root);
+        scan_decls(g, import, import->decls_scope, import->root);
     }
 
     for (; g->use_queue_index < g->use_queue.length; g->use_queue_index += 1) {
src/analyze.hpp
@@ -15,7 +15,6 @@ ErrorMsg *add_node_error(CodeGen *g, AstNode *node, Buf *msg);
 ErrorMsg *add_error_note(CodeGen *g, ErrorMsg *parent_msg, AstNode *node, Buf *msg);
 TypeTableEntry *new_type_table_entry(TypeTableEntryId id);
 TypeTableEntry *get_pointer_to_type(CodeGen *g, TypeTableEntry *child_type, bool is_const);
-Scope *new_scope(AstNode *node, Scope *parent);
 bool is_node_void_expr(AstNode *node);
 uint64_t type_size(CodeGen *g, TypeTableEntry *type_entry);
 TypeTableEntry **get_int_type_ptr(CodeGen *g, bool is_signed, size_t size_in_bits);
@@ -59,11 +58,19 @@ TypeTableEntry *container_ref_type(TypeTableEntry *type_entry);
 bool type_is_complete(TypeTableEntry *type_entry);
 void resolve_container_type(CodeGen *g, TypeTableEntry *type_entry);
 TypeStructField *find_struct_type_field(TypeTableEntry *type_entry, Buf *name);
-Scope *get_container_block_context(TypeTableEntry *type_entry);
+ScopeDecls *get_container_scope(TypeTableEntry *type_entry);
 TypeEnumField *find_enum_type_field(TypeTableEntry *enum_type, Buf *name);
 bool is_container_ref(TypeTableEntry *type_entry);
-void scan_decls(CodeGen *g, ImportTableEntry *import, Scope *context, AstNode *node);
+void scan_decls(CodeGen *g, ImportTableEntry *import, ScopeDecls *decls_scope, AstNode *node);
 void preview_use_decl(CodeGen *g, AstNode *node);
 void resolve_use_decl(CodeGen *g, AstNode *node);
 
+ScopeDecls *create_decls_scope(AstNode *node, Scope *parent);
+Scope *create_block_scope(AstNode *node, Scope *parent);
+Scope *create_defer_scope(AstNode *node, Scope *parent);
+Scope *create_var_scope(AstNode *node, Scope *parent, VariableTableEntry *var);
+Scope *create_cimport_scope(AstNode *node, Scope *parent);
+Scope *create_loop_scope(AstNode *node, Scope *parent);
+Scope *create_fndef_scope(AstNode *node, Scope *parent, FnTableEntry *fn_entry);
+
 #endif
src/codegen.cpp
@@ -227,9 +227,47 @@ void codegen_set_rdynamic(CodeGen *g, bool rdynamic) {
 static void render_const_val(CodeGen *g, TypeTableEntry *type_entry, ConstExprValue *const_val);
 static void render_const_val_global(CodeGen *g, TypeTableEntry *type_entry, ConstExprValue *const_val);
 
+static ZigLLVMDIScope *get_di_scope(CodeGen *g, Scope *scope) {
+    if (scope->di_scope)
+        return scope->di_scope;
+
+    if (scope->node->type == NodeTypeFnDef) {
+        assert(scope->parent);
+        ScopeFnBody *fn_scope = (ScopeFnBody *)scope;
+        FnTableEntry *fn_table_entry = fn_scope->fn_entry;
+        unsigned line_number = fn_table_entry->proto_node->line + 1;
+        unsigned scope_line = line_number;
+        bool is_definition = fn_table_entry->fn_def_node != nullptr;
+        unsigned flags = 0;
+        bool is_optimized = g->is_release_build;
+        ZigLLVMDISubprogram *subprogram = ZigLLVMCreateFunction(g->dbuilder,
+            get_di_scope(g, scope->parent), buf_ptr(&fn_table_entry->symbol_name), "",
+            scope->node->owner->di_file, line_number,
+            fn_table_entry->type_entry->di_type, fn_table_entry->internal_linkage,
+            is_definition, scope_line, flags, is_optimized, nullptr);
+
+        scope->di_scope = ZigLLVMSubprogramToScope(subprogram);
+        ZigLLVMFnSetSubprogram(fn_table_entry->fn_value, subprogram);
+    } else if (scope->node->type == NodeTypeRoot ||
+               scope->node->type == NodeTypeContainerDecl)
+    {
+        scope->di_scope = ZigLLVMFileToScope(scope->node->owner->di_file);
+    } else {
+        assert(scope->parent);
+        ZigLLVMDILexicalBlock *di_block = ZigLLVMCreateLexicalBlock(g->dbuilder,
+            get_di_scope(g, scope->parent),
+            scope->node->owner->di_file,
+            scope->node->line + 1,
+            scope->node->column + 1);
+        scope->di_scope = ZigLLVMLexicalBlockToScope(di_block);
+    }
+
+    return scope->di_scope;
+}
+
 static void set_debug_source_node(CodeGen *g, AstNode *node) {
     assert(node->scope);
-    ZigLLVMSetCurrentDebugLocation(g->builder, node->line + 1, node->column + 1, node->scope->di_scope);
+    ZigLLVMSetCurrentDebugLocation(g->builder, node->line + 1, node->column + 1, get_di_scope(g, node->scope));
 }
 
 static void clear_debug_source_node(CodeGen *g) {
@@ -558,10 +596,9 @@ static LLVMValueRef gen_assign_raw(CodeGen *g, AstNode *source_node,
 }
 
 static void gen_var_debug_decl(CodeGen *g, VariableTableEntry *var) {
-    Scope *scope = var->scope;
     AstNode *source_node = var->decl_node;
     ZigLLVMDILocation *debug_loc = ZigLLVMGetDebugLoc(source_node->line + 1, source_node->column + 1,
-            scope->di_scope);
+        get_di_scope(g, var->parent_scope));
     ZigLLVMInsertDeclareAtEnd(g->dbuilder, var->value_ref, var->di_loc_var, debug_loc,
             LLVMGetInsertBlock(g->builder));
 }
@@ -2133,8 +2170,7 @@ static void gen_global_var(CodeGen *g, VariableTableEntry *var, LLVMValueRef ini
     assert(var->import);
     assert(type_entry);
     bool is_local_to_unit = true;
-    ZigLLVMCreateGlobalVariable(g->dbuilder,
-        var->scope->di_scope, buf_ptr(&var->name),
+    ZigLLVMCreateGlobalVariable(g->dbuilder, get_di_scope(g, var->parent_scope), buf_ptr(&var->name),
         buf_ptr(&var->name), var->import->di_file, var->decl_node->line + 1,
         type_entry->di_type, is_local_to_unit, init_val);
 }
@@ -2328,24 +2364,6 @@ static void do_code_gen(CodeGen *g) {
         AstNodeFnProto *fn_proto = &proto_node->data.fn_proto;
 
         build_all_basic_blocks(g, fn_table_entry);
-
-
-        // Set up debug info for blocks
-        for (size_t bc_i = 0; bc_i < fn_table_entry->all_block_contexts.length; bc_i += 1) {
-            Scope *scope = fn_table_entry->all_block_contexts.at(bc_i);
-
-            if (!scope->di_scope) {
-                ZigLLVMDILexicalBlock *di_block = ZigLLVMCreateLexicalBlock(g->dbuilder,
-                    scope->parent->di_scope,
-                    import->di_file,
-                    scope->node->line + 1,
-                    scope->node->column + 1);
-                scope->di_scope = ZigLLVMLexicalBlockToScope(di_block);
-            }
-
-
-        }
-
         clear_debug_source_node(g);
 
         // allocate temporary stack data
@@ -2383,7 +2401,7 @@ static void do_code_gen(CodeGen *g) {
             if (var->is_inline)
                 continue;
 
-            if (var->scope->node->type == NodeTypeFnDef) {
+            if (var->parent_scope->node->type == NodeTypeFnDef) {
                 assert(var->gen_arg_index != SIZE_MAX);
                 TypeTableEntry *gen_type;
                 if (handle_is_ptr(var->type)) {
@@ -2395,7 +2413,7 @@ static void do_code_gen(CodeGen *g) {
                     unsigned align_bytes = ZigLLVMGetPrefTypeAlignment(g->target_data_ref, var->type->type_ref);
                     LLVMSetAlignment(var->value_ref, align_bytes);
                 }
-                var->di_loc_var = ZigLLVMCreateParameterVariable(g->dbuilder, var->scope->di_scope,
+                var->di_loc_var = ZigLLVMCreateParameterVariable(g->dbuilder, get_di_scope(g, var->parent_scope),
                         buf_ptr(&var->name), import->di_file, var->decl_node->line + 1,
                         gen_type->di_type, !g->strip_debug_symbols, 0, var->gen_arg_index + 1);
 
@@ -2406,7 +2424,7 @@ static void do_code_gen(CodeGen *g) {
                 unsigned align_bytes = ZigLLVMGetPrefTypeAlignment(g->target_data_ref, var->type->type_ref);
                 LLVMSetAlignment(var->value_ref, align_bytes);
 
-                var->di_loc_var = ZigLLVMCreateAutoVariable(g->dbuilder, var->scope->di_scope,
+                var->di_loc_var = ZigLLVMCreateAutoVariable(g->dbuilder, get_di_scope(g, var->parent_scope),
                         buf_ptr(&var->name), import->di_file, var->decl_node->line + 1,
                         var->type->di_type, !g->strip_debug_symbols, 0);
             }
src/hash_map.hpp
@@ -61,6 +61,15 @@ public:
         }
     }
 
+    Entry *put_unique(const K &key, const V &value) {
+        // TODO make this more efficient
+        Entry *entry = internal_get(key);
+        if (entry)
+            return entry;
+        put(key, value);
+        return nullptr;
+    }
+
     const V &get(const K &key) const {
         Entry *entry = internal_get(key);
         if (!entry)
src/ir.cpp
@@ -1211,28 +1211,39 @@ static IrInstruction *ir_build_ref_from(IrBuilder *irb, IrInstruction *old_instr
     return new_instruction;
 }
 
-static void ir_gen_defers_for_block(IrBuilder *irb, Scope *inner_block, Scope *outer_block,
+static void ir_gen_defers_for_block(IrBuilder *irb, Scope *inner_scope, Scope *outer_scope,
         bool gen_error_defers, bool gen_maybe_defers)
 {
-    while (inner_block != outer_block) {
-        if (inner_block->node->type == NodeTypeDefer &&
-           ((inner_block->node->data.defer.kind == ReturnKindUnconditional) ||
-            (gen_error_defers && inner_block->node->data.defer.kind == ReturnKindError) ||
-            (gen_maybe_defers && inner_block->node->data.defer.kind == ReturnKindMaybe)))
+    while (inner_scope != outer_scope) {
+        if (inner_scope->node->type == NodeTypeDefer &&
+           ((inner_scope->node->data.defer.kind == ReturnKindUnconditional) ||
+            (gen_error_defers && inner_scope->node->data.defer.kind == ReturnKindError) ||
+            (gen_maybe_defers && inner_scope->node->data.defer.kind == ReturnKindMaybe)))
         {
-            AstNode *defer_expr_node = inner_block->node->data.defer.expr;
+            AstNode *defer_expr_node = inner_scope->node->data.defer.expr;
             ir_gen_node(irb, defer_expr_node, defer_expr_node->scope);
         }
-        inner_block = inner_block->parent;
+        inner_scope = inner_scope->parent;
     }
 }
 
+static FnTableEntry *scope_fn_entry(Scope *scope) {
+    while (scope) {
+        if (scope->node->type == NodeTypeFnDef) {
+            ScopeFnBody *fn_scope = (ScopeFnBody *)scope;
+            return fn_scope->fn_entry;
+        }
+        scope = scope->parent;
+    }
+    return nullptr;
+}
+
 static IrInstruction *ir_gen_return(IrBuilder *irb, AstNode *node) {
     assert(node->type == NodeTypeReturnExpr);
 
     Scope *scope = node->scope;
 
-    if (!scope->fn_entry) {
+    if (!scope_fn_entry(scope)) {
         add_node_error(irb->codegen, node, buf_sprintf("return expression outside function definition"));
         return irb->codegen->invalid_instruction;
     }
@@ -1243,7 +1254,7 @@ static IrInstruction *ir_gen_return(IrBuilder *irb, AstNode *node) {
             {
                 IrInstruction *return_value;
                 if (expr_node) {
-                    return_value = ir_gen_node(irb, expr_node, scope);
+                    return_value = ir_gen_node(irb, expr_node, node->scope);
                 } else {
                     return_value = ir_build_const_void(irb, node);
                 }
@@ -1264,11 +1275,11 @@ static void ir_set_cursor_at_end(IrBuilder *irb, IrBasicBlock *basic_block) {
     irb->current_basic_block = basic_block;
 }
 
-static VariableTableEntry *add_local_var(CodeGen *codegen, AstNode *node, Scope *scope,
+static VariableTableEntry *add_local_var(CodeGen *codegen, AstNode *node, Scope *parent_scope,
         Buf *name, bool src_is_const, bool gen_is_const, bool is_shadowable, bool is_inline)
 {
     VariableTableEntry *variable_entry = allocate<VariableTableEntry>(1);
-    variable_entry->scope = scope;
+    variable_entry->parent_scope = parent_scope;
     variable_entry->import = node->owner;
     variable_entry->shadowable = is_shadowable;
     variable_entry->mem_slot_index = SIZE_MAX;
@@ -1277,7 +1288,7 @@ static VariableTableEntry *add_local_var(CodeGen *codegen, AstNode *node, Scope
     if (name) {
         buf_init_from_buf(&variable_entry->name, name);
 
-        VariableTableEntry *existing_var = find_variable(codegen, scope, name);
+        VariableTableEntry *existing_var = find_variable(codegen, parent_scope, name);
         if (existing_var && !existing_var->shadowable) {
             ErrorMsg *msg = add_node_error(codegen, node,
                     buf_sprintf("redeclaration of variable '%s'", buf_ptr(name)));
@@ -1291,7 +1302,7 @@ static VariableTableEntry *add_local_var(CodeGen *codegen, AstNode *node, Scope
                         buf_sprintf("variable shadows type '%s'", buf_ptr(&type->name)));
                 variable_entry->type = codegen->builtin_types.entry_invalid;
             } else {
-                AstNode *decl_node = find_decl(scope, name);
+                AstNode *decl_node = find_decl(parent_scope, name);
                 if (decl_node && decl_node->type != NodeTypeVariableDeclaration) {
                     ErrorMsg *msg = add_node_error(codegen, node,
                             buf_sprintf("redefinition of '%s'", buf_ptr(name)));
@@ -1301,28 +1312,32 @@ static VariableTableEntry *add_local_var(CodeGen *codegen, AstNode *node, Scope
             }
         }
 
-        scope->var_table.put(&variable_entry->name, variable_entry);
     } else {
         assert(is_shadowable);
-        // TODO replace _anon with @anon and make sure all tests still pass
+        // TODO make this name not actually be in scope. user should be able to make a variable called "_anon"
+        // might already be solved, let's just make sure it has test coverage
+        // maybe we put a prefix on this so the debug info doesn't clobber user debug info for same named variables
         buf_init_from_str(&variable_entry->name, "_anon");
     }
 
     variable_entry->src_is_const = src_is_const;
     variable_entry->gen_is_const = gen_is_const;
     variable_entry->decl_node = node;
+    variable_entry->child_scope = create_var_scope(node, parent_scope, variable_entry);
 
     return variable_entry;
 }
 
 // Set name to nullptr to make the variable anonymous (not visible to programmer).
-static VariableTableEntry *ir_add_local_var(IrBuilder *irb, AstNode *node, Scope *scope, Buf *name,
+// After you call this function var->child_scope has the variable in scope
+static VariableTableEntry *ir_create_var(IrBuilder *irb, AstNode *node, Scope *scope, Buf *name,
         bool src_is_const, bool gen_is_const, bool is_shadowable, bool is_inline)
 {
     VariableTableEntry *var = add_local_var(irb->codegen, node, scope, name,
             src_is_const, gen_is_const, is_shadowable, is_inline);
     if (is_inline || gen_is_const)
         var->mem_slot_index = exec_next_mem_slot(irb->exec);
+    assert(var->child_scope);
     return var;
 }
 
@@ -1330,7 +1345,7 @@ static IrInstruction *ir_gen_block(IrBuilder *irb, AstNode *block_node) {
     assert(block_node->type == NodeTypeBlock);
 
     Scope *parent_scope = block_node->scope;
-    Scope *outer_block_scope = new_scope(block_node, parent_scope);
+    Scope *outer_block_scope = create_block_scope(block_node, parent_scope);
     Scope *child_scope = outer_block_scope;
 
     IrInstruction *return_value = nullptr;
@@ -1341,6 +1356,9 @@ static IrInstruction *ir_gen_block(IrBuilder *irb, AstNode *block_node) {
             // defer starts a new block context
             child_scope = statement_node->data.defer.child_block;
             assert(child_scope);
+        } else if (return_value->id == IrInstructionIdDeclVar) {
+            IrInstructionDeclVar *decl_var_instruction = (IrInstructionDeclVar *)return_value;
+            child_scope = decl_var_instruction->var->child_scope;
         }
     }
 
@@ -1760,7 +1778,7 @@ static IrInstruction *ir_gen_builtin_fn_call(IrBuilder *irb, AstNode *node) {
                 if (arg0_value == irb->codegen->invalid_instruction)
                     return arg0_value;
 
-                if (node->scope->fn_entry) {
+                if (scope_fn_entry(node->scope)) {
                     add_node_error(irb->codegen, node, buf_sprintf("import valid only at top level scope"));
                     return irb->codegen->invalid_instruction;
                 }
@@ -1999,8 +2017,10 @@ static IrInstruction *ir_gen_var_decl(IrBuilder *irb, AstNode *node) {
     bool is_const = variable_declaration->is_const;
     bool is_extern = variable_declaration->is_extern;
     bool is_inline = ir_should_inline(irb) || variable_declaration->is_inline;
-    VariableTableEntry *var = ir_add_local_var(irb, node, node->scope,
+    VariableTableEntry *var = ir_create_var(irb, node, node->scope,
             variable_declaration->symbol, is_const, is_const, is_shadowable, is_inline);
+    // we detect IrInstructionIdDeclVar in gen_block to make sure the next node
+    // is inside var->child_scope
 
     if (!is_extern && !variable_declaration->expr) {
         var->type = irb->codegen->builtin_types.entry_invalid;
@@ -2079,14 +2099,15 @@ static IrInstruction *ir_gen_for_expr(IrBuilder *irb, AstNode *node) {
     }
     bool is_inline = ir_should_inline(irb) || node->data.for_expr.is_inline;
 
-    Scope *child_scope = new_scope(node, parent_scope);
-    child_scope->parent_loop_node = node;
+    Scope *child_scope = create_loop_scope(node, parent_scope);
     elem_node->scope = child_scope;
 
     // TODO make it an error to write to element variable or i variable.
     Buf *elem_var_name = elem_node->data.symbol_expr.symbol;
-    node->data.for_expr.elem_var = ir_add_local_var(irb, elem_node, child_scope, elem_var_name,
+    node->data.for_expr.elem_var = ir_create_var(irb, elem_node, child_scope, elem_var_name,
             true, false, false, is_inline);
+    child_scope = node->data.for_expr.elem_var->child_scope;
+
     IrInstruction *undefined_value = ir_build_const_undefined(irb, elem_node);
     ir_build_var_decl(irb, elem_node, node->data.for_expr.elem_var, elem_var_type, undefined_value); 
     IrInstruction *elem_var_ptr = ir_build_var_ptr(irb, node, node->data.for_expr.elem_var);
@@ -2096,13 +2117,15 @@ static IrInstruction *ir_gen_for_expr(IrBuilder *irb, AstNode *node) {
         index_var_source_node = index_node;
         Buf *index_var_name = index_node->data.symbol_expr.symbol;
         index_node->scope = child_scope;
-        node->data.for_expr.index_var = ir_add_local_var(irb, index_node, child_scope, index_var_name,
+        node->data.for_expr.index_var = ir_create_var(irb, index_node, child_scope, index_var_name,
                 true, false, false, is_inline);
     } else {
         index_var_source_node = node;
-        node->data.for_expr.index_var = ir_add_local_var(irb, node, child_scope, nullptr,
+        node->data.for_expr.index_var = ir_create_var(irb, node, child_scope, nullptr,
                 true, false, true, is_inline);
     }
+    child_scope = node->data.for_expr.index_var->child_scope;
+
     IrInstruction *usize = ir_build_const_type(irb, node, irb->codegen->builtin_types.entry_usize);
     IrInstruction *zero = ir_build_const_usize(irb, node, 0);
     IrInstruction *one = ir_build_const_usize(irb, node, 1);
@@ -2159,10 +2182,11 @@ static IrInstruction *ir_gen_this_literal(IrBuilder *irb, AstNode *node) {
     if (!scope->parent)
         return ir_build_const_import(irb, node, node->owner);
 
-    if (scope->fn_entry && (!scope->parent->fn_entry ||
-        (scope->parent->parent && !scope->parent->parent->fn_entry)))
+    FnTableEntry *fn_entry = scope_fn_entry(scope);
+    if (fn_entry && scope->parent && scope->parent->parent &&
+        !scope_fn_entry(scope->parent->parent))
     {
-        return ir_build_const_fn(irb, node, scope->fn_entry);
+        return ir_build_const_fn(irb, node, fn_entry);
     }
 
     if (scope->node->type == NodeTypeContainerDecl) {
@@ -2308,15 +2332,15 @@ static IrInstruction *ir_gen_if_var_expr(IrBuilder *irb, AstNode *node) {
         if (var_type == irb->codegen->invalid_instruction)
             return irb->codegen->invalid_instruction;
     }
-    Scope *child_scope = new_scope(node, node->scope);
     bool is_shadowable = false;
     bool is_const = var_decl->is_const;
-    VariableTableEntry *var = ir_add_local_var(irb, node, child_scope,
+    VariableTableEntry *var = ir_create_var(irb, node, node->scope,
             var_decl->symbol, is_const, is_const, is_shadowable, is_inline);
+
     IrInstruction *var_ptr_value = ir_build_unwrap_maybe(irb, node, expr_value, false);
     IrInstruction *var_value = var_is_ptr ? var_ptr_value : ir_build_load_ptr(irb, node, var_ptr_value);
     ir_build_var_decl(irb, node, var, var_type, var_value); 
-    IrInstruction *then_expr_result = ir_gen_node(irb, then_node, child_scope);
+    IrInstruction *then_expr_result = ir_gen_node(irb, then_node, var->child_scope);
     if (then_expr_result == irb->codegen->invalid_instruction)
         return then_expr_result;
     IrBasicBlock *after_then_block = irb->current_basic_block;
@@ -2360,11 +2384,11 @@ static bool ir_gen_switch_prong_expr(IrBuilder *irb, AstNode *switch_node, AstNo
         Buf *var_name = var_symbol_node->data.symbol_expr.symbol;
         bool var_is_ptr = prong_node->data.switch_prong.var_is_ptr;
 
-        child_scope = new_scope(switch_node, switch_node->scope);
         bool is_shadowable = false;
         bool is_const = true;
-        VariableTableEntry *var = ir_add_local_var(irb, var_symbol_node, child_scope,
+        VariableTableEntry *var = ir_create_var(irb, var_symbol_node, switch_node->scope,
                 var_name, is_const, is_const, is_shadowable, is_inline);
+        child_scope = var->child_scope;
         IrInstruction *var_value;
         if (prong_value) {
             IrInstruction *var_ptr_value = ir_build_switch_var(irb, var_symbol_node, target_value_ptr, prong_value);
@@ -2542,14 +2566,25 @@ static IrInstruction *ir_gen_switch_expr(IrBuilder *irb, AstNode *node) {
     return ir_build_phi(irb, node, incoming_blocks.length, incoming_blocks.items, incoming_values.items);
 }
 
-static LabelTableEntry *find_label(IrExecutable *exec, Scope *orig_context, Buf *name) {
-    Scope *context = orig_context;
-    while (context) {
-        auto entry = context->label_table.maybe_get(name);
-        if (entry) {
-            return entry->value;
+static LabelTableEntry *find_label(IrExecutable *exec, Scope *scope, Buf *name) {
+    while (scope) {
+        if (scope->node->type == NodeTypeBlock) {
+            ScopeBlock *block_scope = (ScopeBlock *)scope;
+            auto entry = block_scope->label_table.maybe_get(name);
+            if (entry)
+                return entry->value;
         }
-        context = context->parent;
+        scope = scope->parent;
+    }
+
+    return nullptr;
+}
+
+static ScopeBlock *find_block_scope(IrExecutable *exec, Scope *scope) {
+    while (scope) {
+        if (scope->node->type == NodeTypeBlock)
+            return (ScopeBlock *)scope;
+        scope = scope->parent;
     }
     return nullptr;
 }
@@ -2571,7 +2606,8 @@ static IrInstruction *ir_gen_label(IrBuilder *irb, AstNode *node) {
         add_error_note(irb->codegen, msg, existing_label->decl_node, buf_sprintf("other label here"));
         return irb->codegen->invalid_instruction;
     } else {
-        node->scope->label_table.put(label_name, label);
+        ScopeBlock *scope_block = find_block_scope(irb->exec, node->scope);
+        scope_block->label_table.put(label_name, label);
     }
 
     bool is_inline = ir_should_inline(irb);
@@ -2778,9 +2814,9 @@ IrInstruction *ir_gen_fn(CodeGen *codegn, FnTableEntry *fn_entry) {
     assert(fn_def_node->type == NodeTypeFnDef);
 
     AstNode *body_node = fn_def_node->data.fn_def.body;
-    Scope *scope = fn_def_node->data.fn_def.scope;
+    Scope *child_scope = fn_def_node->data.fn_def.child_scope;
 
-    return ir_gen(codegn, body_node, scope, ir_executable);
+    return ir_gen(codegn, body_node, child_scope, ir_executable);
 }
 
 static IrInstruction *ir_eval_fn(IrAnalyze *ira, IrInstruction *source_instruction,
@@ -3023,8 +3059,10 @@ static IrInstruction *ir_resolve_cast(IrAnalyze *ira, IrInstruction *source_inst
     } else {
         IrInstruction *result = ir_build_cast(&ira->new_irb, source_instr->source_node, wanted_type, value, cast_op);
         result->type_entry = wanted_type;
-        if (need_alloca && source_instr->source_node->scope->fn_entry) {
-            source_instr->source_node->scope->fn_entry->alloca_list.append(result);
+        if (need_alloca) {
+            FnTableEntry *fn_entry = scope_fn_entry(source_instr->source_node->scope);
+            if (fn_entry)
+                fn_entry->alloca_list.append(result);
         }
         return result;
     }
@@ -3550,7 +3588,8 @@ static TypeTableEntry *ir_analyze_ref(IrAnalyze *ira, IrInstruction *source_inst
         ir_link_new_instruction(value, source_instruction);
         return ptr_type;
     } else {
-        FnTableEntry *fn_entry = source_instruction->source_node->scope->fn_entry;
+        FnTableEntry *fn_entry = scope_fn_entry(source_instruction->source_node->scope);
+        assert(fn_entry);
         IrInstruction *new_instruction = ir_build_ref_from(&ira->new_irb, source_instruction, value);
         fn_entry->alloca_list.append(new_instruction);
         return ptr_type;
@@ -4098,8 +4137,9 @@ static TypeTableEntry *ir_analyze_instruction_decl_var(IrAnalyze *ira, IrInstruc
     ir_build_var_decl_from(&ira->new_irb, &decl_var_instruction->base, var, var_type, casted_init_value);
 
     Scope *scope = decl_var_instruction->base.source_node->scope;
-    if (scope->fn_entry)
-        scope->fn_entry->variable_list.append(var);
+    FnTableEntry *fn_entry = scope_fn_entry(scope);
+    if (fn_entry)
+        fn_entry->variable_list.append(var);
 
     return ira->codegen->builtin_types.entry_void;
 }
@@ -4200,8 +4240,11 @@ static TypeTableEntry *ir_analyze_fn_call(IrAnalyze *ira, IrInstructionCall *cal
     IrInstruction *new_call_instruction = ir_build_call_from(&ira->new_irb, &call_instruction->base,
             fn_entry, fn_ref, call_param_count, casted_args);
 
-    if (type_has_bits(return_type) && handle_is_ptr(return_type))
-        call_instruction->base.source_node->scope->fn_entry->alloca_list.append(new_call_instruction);
+    if (type_has_bits(return_type) && handle_is_ptr(return_type)) {
+        FnTableEntry *fn_entry = scope_fn_entry(call_instruction->base.source_node->scope);
+        assert(fn_entry);
+        fn_entry->alloca_list.append(new_call_instruction);
+    }
 
     return ir_finish_anal(ira, return_type);
 }
@@ -4732,7 +4775,8 @@ static TypeTableEntry *ir_analyze_var_ptr(IrAnalyze *ira, IrInstruction *instruc
         return var->type;
 
     ConstExprValue *mem_slot = nullptr;
-    if (var->scope->fn_entry) {
+    FnTableEntry *fn_entry = scope_fn_entry(var->parent_scope);
+    if (fn_entry) {
         // TODO once the analyze code is fully ported over to IR we won't need this SIZE_MAX thing.
         if (var->mem_slot_index != SIZE_MAX)
             mem_slot = &ira->exec_context.mem_slot_list[var->mem_slot_index];
@@ -4879,9 +4923,8 @@ static TypeTableEntry *ir_analyze_container_member_access_inner(IrAnalyze *ira,
     IrInstruction *container_ptr, TypeTableEntry *container_type)
 {
     if (!is_slice(bare_struct_type)) {
-        Scope *container_block_context = get_container_block_context(bare_struct_type);
-        assert(container_block_context);
-        auto entry = container_block_context->decl_table.maybe_get(field_name);
+        ScopeDecls *container_scope = get_container_scope(bare_struct_type);
+        auto entry = container_scope->decl_table.maybe_get(field_name);
         AstNode *fn_decl_node = entry ? entry->value : nullptr;
         if (fn_decl_node && fn_decl_node->type == NodeTypeFnProto) {
             resolve_top_level_decl(ira->codegen, fn_decl_node, false);
@@ -5023,8 +5066,8 @@ static TypeTableEntry *ir_analyze_instruction_field_ptr(IrAnalyze *ira, IrInstru
         } else if (child_type->id == TypeTableEntryIdEnum) {
             zig_panic("TODO enum type field");
         } else if (child_type->id == TypeTableEntryIdStruct) {
-            Scope *container_block_context = get_container_block_context(child_type);
-            auto entry = container_block_context->decl_table.maybe_get(field_name);
+            ScopeDecls *container_scope = get_container_scope(child_type);
+            auto entry = container_scope->decl_table.maybe_get(field_name);
             AstNode *decl_node = entry ? entry->value : nullptr;
             if (decl_node) {
                 bool depends_on_compile_var = container_ptr->static_value.depends_on_compile_var;
@@ -5055,7 +5098,7 @@ static TypeTableEntry *ir_analyze_instruction_field_ptr(IrAnalyze *ira, IrInstru
         ImportTableEntry *namespace_import = namespace_val->data.x_import;
 
         bool depends_on_compile_var = container_ptr->static_value.depends_on_compile_var;
-        AstNode *decl_node = find_decl(namespace_import->scope, field_name);
+        AstNode *decl_node = find_decl(&namespace_import->decls_scope->base, field_name);
         if (!decl_node) {
             // we must now resolve all the use decls
             for (size_t i = 0; i < namespace_import->use_decls.length; i += 1) {
@@ -5066,7 +5109,7 @@ static TypeTableEntry *ir_analyze_instruction_field_ptr(IrAnalyze *ira, IrInstru
                 }
                 resolve_use_decl(ira->codegen, use_decl_node);
             }
-            decl_node = find_decl(namespace_import->scope, field_name);
+            decl_node = find_decl(&namespace_import->decls_scope->base, field_name);
         }
         if (decl_node) {
             TopLevelDecl *tld = get_as_top_level_decl(decl_node);
@@ -5327,15 +5370,15 @@ static TypeTableEntry *ir_analyze_instruction_set_debug_safety(IrAnalyze *ira,
     if (target_type->id == TypeTableEntryIdBlock) {
         target_context = target_val->data.x_block;
     } else if (target_type->id == TypeTableEntryIdFn) {
-        target_context = target_val->data.x_fn->fn_def_node->data.fn_def.scope;
+        target_context = target_val->data.x_fn->fn_def_node->data.fn_def.child_scope;
     } else if (target_type->id == TypeTableEntryIdMetaType) {
         TypeTableEntry *type_arg = target_val->data.x_type;
         if (type_arg->id == TypeTableEntryIdStruct) {
-            target_context = type_arg->data.structure.scope;
+            target_context = &type_arg->data.structure.decls_scope->base;
         } else if (type_arg->id == TypeTableEntryIdEnum) {
-            target_context = type_arg->data.enumeration.scope;
+            target_context = &type_arg->data.enumeration.decls_scope->base;
         } else if (type_arg->id == TypeTableEntryIdUnion) {
-            target_context = type_arg->data.unionation.scope;
+            target_context = &type_arg->data.unionation.decls_scope->base;
         } else {
             add_node_error(ira->codegen, target_instruction->source_node,
                 buf_sprintf("expected scope reference, found type '%s'", buf_ptr(&type_arg->name)));
@@ -5966,7 +6009,7 @@ static TypeTableEntry *ir_analyze_instruction_import(IrAnalyze *ira, IrInstructi
     ImportTableEntry *target_import = add_source_file(ira->codegen, target_package,
             abs_full_path, search_dir, import_target_path, import_code);
 
-    scan_decls(ira->codegen, target_import, target_import->scope, target_import->root);
+    scan_decls(ira->codegen, target_import, target_import->decls_scope, target_import->root);
 
     ConstExprValue *out_val = ir_build_const_from(ira, &import_instruction->base, depends_on_compile_var);
     out_val->data.x_import = target_import;
@@ -6021,7 +6064,7 @@ static TypeTableEntry *ir_analyze_container_init_fields(IrAnalyze *ira, IrInstru
 
     IrInstructionStructInitField *new_fields = allocate<IrInstructionStructInitField>(actual_field_count);
 
-    FnTableEntry *fn_entry = instruction->source_node->scope->fn_entry;
+    FnTableEntry *fn_entry = scope_fn_entry(instruction->source_node->scope);
     bool outside_fn = (fn_entry == nullptr);
 
     ConstExprValue const_val = {};
@@ -6124,7 +6167,7 @@ static TypeTableEntry *ir_analyze_instruction_container_init_list(IrAnalyze *ira
         const_val.data.x_array.elements = allocate<ConstExprValue>(elem_count);
         const_val.data.x_array.size = elem_count;
 
-        FnTableEntry *fn_entry = instruction->base.source_node->scope->fn_entry;
+        FnTableEntry *fn_entry = scope_fn_entry(instruction->base.source_node->scope);
         bool outside_fn = (fn_entry == nullptr);
 
         IrInstruction **new_items = allocate<IrInstruction *>(elem_count);
src/parseh.cpp
@@ -817,7 +817,7 @@ static TypeTableEntry *resolve_enum_decl(Context *c, const EnumDecl *enum_decl)
     const EnumDecl *enum_def = enum_decl->getDefinition();
     if (!enum_def) {
         TypeTableEntry *enum_type = get_partial_container_type(c->codegen, c->import,
-                c->import->scope,
+                &c->import->decls_scope->base,
                 ContainerKindEnum, c->source_node, buf_ptr(full_type_name));
         c->enum_type_table.put(bare_name, enum_type);
         c->decl_table.put(enum_decl, enum_type);
@@ -842,7 +842,7 @@ static TypeTableEntry *resolve_enum_decl(Context *c, const EnumDecl *enum_decl)
 
     if (pure_enum) {
         TypeTableEntry *enum_type = get_partial_container_type(c->codegen, c->import,
-                c->import->scope,
+                &c->import->decls_scope->base,
                 ContainerKindEnum, c->source_node, buf_ptr(full_type_name));
         c->enum_type_table.put(bare_name, enum_type);
         c->decl_table.put(enum_decl, enum_type);
@@ -1002,7 +1002,7 @@ static TypeTableEntry *resolve_record_decl(Context *c, const RecordDecl *record_
 
 
     TypeTableEntry *struct_type = get_partial_container_type(c->codegen, c->import,
-            c->import->scope, ContainerKindStruct, c->source_node, buf_ptr(full_type_name));
+            &c->import->decls_scope->base, ContainerKindStruct, c->source_node, buf_ptr(full_type_name));
 
     c->struct_type_table.put(bare_name, struct_type);
     c->decl_table.put(record_decl, struct_type);