codegen: add incomplete generation of expressions

src/codegen.zig

@@ -16,6 +16,43 @@ pub const Codegen = struct {
         return Codegen{ .allocator = allocator };
     }
 
+    fn genExpr(self: *Codegen, builder: var, expr: *const ast.Expr) !llvm.LLVMValueRef {
+        // TODO if expr is Variable, we should do a variable lookup
+        // in a symbol table, going up in scope, etc.
+
+        // TODO VarDecl add things to the symbol table
+        // TODO Assign modify symbol table
+
+        // TODO Calls fetch symbol table, check arity of it at codegen level
+        switch (expr.*) {
+
+            // TODO handle all literals, construct llvm values for them
+            .Literal => |literal| {},
+            .Binary => |binary| {
+                var left = try self.genExpr(builder, binary.left);
+                var right = try self.genExpr(builder, binary.right);
+
+                return switch (binary.op.lexeme[0]) {
+                    // TODO other operators
+                    '+' => llvm.LLVMBuildAdd(builder, left, right, c"addtmp"),
+
+                    // TODO codegen errors
+                    else => @panic("invalid binary operator"),
+                };
+            },
+
+            // TODO codegen errors
+            else => @panic("invalid expr"),
+        }
+    }
+
+    fn genFuncStmt(self: *Codegen, builder: var, stmt: *const ast.Stmt) !void {
+        switch (stmt.*) {
+            .Expr => |expr| try self.genExpr(builder, expr),
+            else => unreachable,
+        }
+    }
+
     fn genNode(
         self: *Codegen,
         mod: llvm.LLVMModuleRef,
@@ -50,6 +87,11 @@ pub const Codegen = struct {
                 var builder = llvm.LLVMCreateBuilder();
                 llvm.LLVMPositionBuilderAtEnd(builder, entry);
 
+                for (decl.body.toSlice()) |stmt| {
+                    // TODO custom function context for us
+                    try self.genFuncStmt(builder, stmt);
+                }
+
                 // TODO codegen decl.body
                 var tmp = llvm.LLVMBuildAdd(
                     builder,

src/main.zig

@@ -46,6 +46,9 @@ pub fn run(allocator: *std.mem.Allocator, slice: []const u8) !Result {
     std.debug.warn("parse tree\n");
     printer.printNode(root.?, 0);
 
+    // TODO type pass
+    // TODO variable pass
+
     var cgen = codegen.Codegen.init(allocator);
     try cgen.gen(root.?);