codegen: add emitting of const declarations

src/codegen.zig

@@ -316,6 +316,25 @@ pub const Codegen = struct {
             // NOTE: enums don't have specific llvm ir code generated for them
             .Enum => {},
 
+            .ConstDecl => |constdecls| {
+                for (constdecls.toSlice()) |constdecl| {
+                    const name = constdecl.name.lexeme;
+
+                    var const_type = self.ctx.symbol_table.get(name).?.value;
+                    var const_llvm_type = try self.typeToLLVM(const_type.Const);
+
+                    const const_name = try std.cstr.addNullByte(self.allocator, name);
+                    errdefer self.allocator.free(const_name);
+
+                    var global = llvm.LLVMAddGlobal(mod, const_llvm_type, const_name.ptr);
+
+                    var builder = llvm.LLVMCreateBuilder();
+                    var expr_llvm_val = try self.emitExpr(builder, constdecl.expr);
+
+                    llvm.LLVMSetInitializer(global, expr_llvm_val);
+                }
+            },
+
             else => {
                 std.debug.warn("TODO handle node type {}\n", @tagName(node.*));
                 return;