analysis: add analysis of Assign expressions

examples/hello.ry

@@ -1,6 +1,7 @@
 fn f() i32 {
     var a = 3;
-    return a;
+    a = 2;
+    return a + 23;
 }
 
 fn f2() i32 {

src/analysis.zig

@@ -339,10 +339,17 @@ pub const TypeSolver = struct {
                 }
             },
 
-            else => {
-                std.debug.warn("TODO resolve expr {}\n", ast.ExprType(expr.*));
-                unreachable;
+            .Assign => |assign| {
+                var var_type = ctx.current_scope.?.env.get(
+                    assign.name.lexeme,
+                ).?.value;
+
+                var value_type = try self.resolveExprType(ctx, assign.value);
+                try self.expectSymUnTypeEqual(var_type, value_type);
+                return var_type;
             },
+
+            .Set => @panic("TODO analysis of Set exprs"),
         }
     }
 

src/codegen.zig

@@ -220,6 +220,8 @@ pub const Codegen = struct {
                 // we will also need to repeat the step for the type resolver
 
                 //var typ = self.findCurrent(assign.name);
+                @panic("TODO finish Assign emitting");
+
                 var assign_expr = try self.emitExpr(builder, assign.value);
 
                 // TODO rm null