reassign values

compiler/compiler.go

@@ -198,6 +198,25 @@ func (c *Compiler) Compile(node ast.Node) error {
 			}
 		}
 
+	case *ast.AssignmentStatement:
+		symbol, ok := c.symbolTable.Resolve(node.Name.Value)
+		if !ok {
+			return fmt.Errorf("undefined variable %s", node.Value)
+		}
+
+		err := c.Compile(node.Value)
+		if err != nil {
+			return err
+		}
+
+		if symbol.Scope == GlobalScope {
+			c.emit(code.OpGetGlobal, symbol.Index)
+		} else {
+			c.emit(code.OpGetLocal, symbol.Index)
+		}
+
+		c.emit(code.OpAssign)
+
 	case *ast.LetStatement:
 		symbol, ok := c.symbolTable.Resolve(node.Name.Value)
 		if !ok {

compiler/compiler_test.go

@@ -767,6 +767,102 @@ func TestFunctionCalls(t *testing.T) {
 	runCompilerTests(t, tests)
 }
 
+func TestAssignmentStatementScopes(t *testing.T) {
+	tests := []compilerTestCase{
+		{
+			input: `
+            let num = 0;
+            fn() { num  = 55; }
+            `,
+			expectedConstants: []interface{}{
+				0,
+				55,
+				[]code.Instructions{
+					code.Make(code.OpConstant, 1),
+					code.Make(code.OpGetGlobal, 0),
+					code.Make(code.OpAssign),
+					code.Make(code.OpReturn),
+				},
+			},
+			expectedInstructions: []code.Instructions{
+				code.Make(code.OpConstant, 0),
+				code.Make(code.OpSetGlobal, 0),
+				code.Make(code.OpClosure, 2, 0),
+				code.Make(code.OpPop),
+			},
+		},
+
+		{
+			input: `
+			            fn() {
+			                let num = 55;
+			                num
+			            }
+			            `,
+			expectedConstants: []interface{}{
+				55,
+				[]code.Instructions{
+					code.Make(code.OpConstant, 0),
+					code.Make(code.OpSetLocal, 0),
+					code.Make(code.OpGetLocal, 0),
+					code.Make(code.OpReturnValue),
+				},
+			},
+			expectedInstructions: []code.Instructions{
+				code.Make(code.OpClosure, 1, 0),
+				code.Make(code.OpPop),
+			},
+		},
+		{
+			input: `
+			            fn() {
+			                let a = 55;
+			                let b = 77;
+			                a + b
+			            }
+			            `,
+			expectedConstants: []interface{}{
+				55,
+				77,
+				[]code.Instructions{
+					code.Make(code.OpConstant, 0),
+					code.Make(code.OpSetLocal, 0),
+					code.Make(code.OpConstant, 1),
+					code.Make(code.OpSetLocal, 1),
+					code.Make(code.OpGetLocal, 0),
+					code.Make(code.OpGetLocal, 1),
+					code.Make(code.OpAdd),
+					code.Make(code.OpReturnValue),
+				},
+			},
+			expectedInstructions: []code.Instructions{
+				code.Make(code.OpClosure, 2, 0),
+				code.Make(code.OpPop),
+			},
+		},
+		{
+			input: `
+						let a = 0;
+						let a = a + 1;
+						`,
+			expectedConstants: []interface{}{
+				0,
+				1,
+			},
+			expectedInstructions: []code.Instructions{
+				code.Make(code.OpConstant, 0),
+				code.Make(code.OpSetGlobal, 0),
+				code.Make(code.OpGetGlobal, 0),
+				code.Make(code.OpConstant, 1),
+				code.Make(code.OpAdd),
+				code.Make(code.OpSetGlobal, 0),
+			},
+		},
+	}
+
+	runCompilerTests(t, tests)
+}
+
 func TestLetStatementScopes(t *testing.T) {
 	tests := []compilerTestCase{
 		{