Variable reassignment

Nub.Lang/Nub.Lang/Generation/Generator.cs

@@ -10,7 +10,7 @@ public class Generator
     private readonly IReadOnlyCollection<DefinitionNode> _definitions;
     private readonly SymbolTable _symbolTable;
     private readonly StringBuilder _builder;
-    private Dictionary<string, string> _strings;
+    private readonly Dictionary<string, string> _strings;
     private int _stringIndex;
     
     public Generator(IReadOnlyCollection<DefinitionNode> definitions)
@@ -73,13 +73,13 @@ public class Generator
                             strlen:
                                 push rcx            ; save and clear out counter
                                 xor rcx, rcx
-                            .strlen_next:
+                            strlen_next:
                                 cmp [rdi], byte 0   ; null byte yet?
-                                jz .strlen_null     ; yes, get out
+                                jz strlen_null     ; yes, get out
                                 inc rcx             ; char is ok, count it
                                 inc rdi             ; move to next char
-                                jmp .strlen_next    ; process again
-                            .strlen_null:
+                                jmp strlen_next    ; process again
+                            strlen_null:
                                 mov rax, rcx        ; rcx = the length (put in rax)
                                 pop rcx             ; restore rcx
                                 ret                 ; get out
@@ -154,6 +154,9 @@ public class Generator
             case VariableAssignmentNode variableAssignment:
                 GenerateVariableAssignment(func, variableAssignment);
                 break;
+            case VariableReassignmentNode variableReassignment:
+                GenerateVariableReassignment(variableReassignment, func);
+                break;
             default:
                 throw new ArgumentOutOfRangeException(nameof(statement));
         }
@@ -171,8 +174,15 @@ public class Generator
 
     private void GenerateVariableAssignment(Func func, VariableAssignmentNode variableAssignment)
     {
-        GenerateExpression(variableAssignment.Value, func);
         var variable = func.ResolveLocalVariable(variableAssignment.Name);
+        GenerateExpression(variableAssignment.Value, func);
+        _builder.AppendLine($"    mov [rbp - {variable.Offset}], rax");
+    }
+
+    private void GenerateVariableReassignment(VariableReassignmentNode variableReassignment, Func func)
+    {
+        var variable = func.ResolveLocalVariable(variableReassignment.Name);
+        GenerateExpression(variableReassignment.Value, func);
         _builder.AppendLine($"    mov [rbp - {variable.Offset}], rax");
     }
 

Nub.Lang/Nub.Lang/Input/program.nub

@@ -4,9 +4,12 @@ let STD_OUT = 1;
 let STD_ERR = 2;
 
 func main() {
-    write("test\n");
+    let x = "test\n";
+    write(x);
+    x = "uwu\n";
+    write(x);
 }
 
-func write(msg: String): int64 {
-    return syscall(SYS_WRITE, STD_OUT, msg, strlen(msg));
+func write(msg: String) {
+    syscall(SYS_WRITE, STD_OUT, msg, strlen(msg));
 }

Nub.Lang/Nub.Lang/Parsing/Parser.cs

@@ -109,11 +109,17 @@ public class Parser
                         return new FuncCallStatementNode(new FuncCall(identifier.Value, parameters));
                     }
                     case Symbol.Assign:
-                        throw new NotImplementedException();
+                    {
+                        var value = ParseExpression();
+                        ExpectSymbol(Symbol.Semicolon);
+                        return new VariableReassignmentNode(identifier.Value, value);
+                    }
                     default:
+                    {
                         throw new Exception($"Unexpected symbol {symbol.Symbol}");
                     }
                 }
+            }
             case SymbolToken symbol:
             {
                 switch (symbol.Symbol)
@@ -144,9 +150,11 @@ public class Parser
                 }   
             }
             default:
+            {
                 throw new Exception($"Unexpected token type {token.GetType().Name}");
             }
         }
+    }
 
     private ExpressionNode ParseExpression()
     {

Nub.Lang/Nub.Lang/Parsing/VariableReassignmentNode.cs

@@ -0,0 +1,7 @@
+namespace Nub.Lang.Parsing;
+
+public class VariableReassignmentNode(string name, ExpressionNode value) : StatementNode
+{
+    public string Name { get; } = name;
+    public ExpressionNode Value { get; } = value;
+}

Nub.Lang/Nub.Lang/Typing/ExpressionTyper.cs

@@ -68,6 +68,9 @@ public class ExpressionTyper
             case VariableAssignmentNode variableAssignment:
                 PopulateVariableAssignment(variableAssignment);
                 break;
+            case VariableReassignmentNode variableReassignment:
+                PopulateVariableReassignment(variableReassignment);
+                break;
             default:
                 throw new ArgumentOutOfRangeException(nameof(statement));
         }
@@ -103,6 +106,11 @@ public class ExpressionTyper
         _variables.Push(new Variable(variableAssignment.Name, variableAssignment.Value.Type));
     }
 
+    private void PopulateVariableReassignment(VariableReassignmentNode variableReassignment)
+    {
+        PopulateExpression(variableReassignment.Value);
+    }
+
     private void PopulateExpression(ExpressionNode expression)
     {
         switch (expression)