From c9e7390f06ff3b03b7d2a79acc14204ff13acd1a Mon Sep 17 00:00:00 2001
From: Sasha Koshka <sashakoshka@tebibyte.media>
Date: Sat, 23 Sep 2023 00:48:50 -0400
Subject: [PATCH] Added scope information to some entities

---
 entity/expression.go |  4 ++++
 entity/scope.go      | 31 +++++++++++++++++++++++++++++++
 entity/toplevel.go   |  6 ++++++
 3 files changed, 41 insertions(+)
 create mode 100644 entity/scope.go

diff --git a/entity/expression.go b/entity/expression.go
index c69b81d..7fc3461 100644
--- a/entity/expression.go
+++ b/entity/expression.go
@@ -192,8 +192,12 @@ func (this *Operation) String () string {
 // equivalent to those of its last expression. A block is never a valid location
 // expression.
 type Block struct {
+	// Syntax
 	Pos lexer.Position
 	Steps []Statement `parser:" '{' @@* '}' "`
+
+	// Semantics
+	Scope
 }
 func (*Block) expression(){}
 func (*Block) statement(){}
diff --git a/entity/scope.go b/entity/scope.go
new file mode 100644
index 0000000..ee13d10
--- /dev/null
+++ b/entity/scope.go
@@ -0,0 +1,31 @@
+package entity
+
+// Scoped represents any entity that has its own scope.
+type Scoped interface {
+	// Variable returns the declaration of the variable with the given name.
+	// If no variable is found in this scope, it returns nil. Only the scope
+	// in this entity is searched.
+	Variable (name string) *Declaration
+
+	// AddVariable adds a variable to this entity's scope.
+	AddVariable (name string, declaration *Declaration)
+}
+
+// Scope implements a scope.
+type Scope struct {
+	variables map[string] *Declaration
+}
+
+func (this *Scope) Variable (name string) *Declaration {
+	if this.variables == nil {
+		return nil
+	}
+	return this.variables[name]
+}
+
+func (this *Scope) AddVariable (name string, declaration *Declaration) {
+	if this.variables == nil {
+		this.variables = make(map[string] *Declaration)
+	}
+	this.variables[name] = declaration
+}
diff --git a/entity/toplevel.go b/entity/toplevel.go
index 5e5f41e..e8df198 100644
--- a/entity/toplevel.go
+++ b/entity/toplevel.go
@@ -41,6 +41,9 @@ type Function struct {
 	Public     bool       `parser:" @'+'?       "`
 	Signature  *Signature `parser:" @@          "`
 	Body       Expression `parser:" ( '=' @@ )? "`
+
+	// Semantics
+	Scope
 }
 func (*Function) topLevel(){}
 func (this *Function) String () string {
@@ -62,6 +65,9 @@ type Method struct {
 	TypeName   string     `parser:" @Ident      "`
 	Signature  *Signature `parser:" '.' @@      "`
 	Body       Expression `parser:" ( '=' @@ )? "`
+
+	// Semantics
+	Scope
 }
 func (*Method) topLevel(){}
 func (this *Method) String () string {