fix(compiler): duplicate diagnostics when typechecking (BoundaryML#2535)

Closes: BoundaryML#2511

Fixes the fact that we were emitting diagnostics for error branches that
already had emitted a diagnostic

---------

Co-authored-by: Antonio Sarosi <[email protected]>

Author: AntennaeVY

engine/baml-compiler/src/thir/typecheck.rs

@@ -2363,20 +2363,6 @@ pub fn typecheck_expression(
 
                 _ => {
                     match (left.meta().1.as_ref(), right.meta().1.as_ref()) {
-                        (None, Some(_)) => {
-                            diagnostics.push_error(DatamodelError::new_validation_error(
-                                "Invalid binary operation: cannot infer type of left operand",
-                                span.clone(),
-                            ))
-                        }
-
-                        (Some(_), None) => {
-                            diagnostics.push_error(DatamodelError::new_validation_error(
-                                "Invalid binary operation: cannot infer type of right operand",
-                                span.clone(),
-                            ))
-                        }
-
                         (Some(left_type), Some(right_type)) => {
                             diagnostics.push_error(DatamodelError::new_validation_error(
                                 &format!("Invalid binary operation ({operator}) on different types: {} {operator} {}",
@@ -2387,11 +2373,9 @@ pub fn typecheck_expression(
                             ));
                         }
 
-                        (None, None) => {
-                            diagnostics.push_error(DatamodelError::new_validation_error(
-                                "Invalid binary operation: cannot infer type of operands",
-                                span.clone(),
-                            ));
+                        _ => {
+                            // We won't emit more diagnostics here because if either of the branches
+                            // has no type we've already emitted an error for that branch
                         }
                     };
 

engine/baml-lib/baml/tests/validation_files/loops/c_for.baml

@@ -80,12 +80,6 @@ function BreakContinue() -> int {
 // 20 | 
 // 21 | for (; i <= 10; i += 1) {
 //    | 
-// error: Error validating: Invalid binary operation: cannot infer type of left operand
-//   -->  loops/c_for.baml:21
-//    | 
-// 20 | 
-// 21 | for (; i <= 10; i += 1) {
-//    | 
 // error: Error validating: Unknown variable i
 //   -->  loops/c_for.baml:21
 //    | 

engine/baml-lib/baml/tests/validation_files/loops/header_requires_let_negative.baml

@@ -53,12 +53,6 @@ function MissingLetAfter() -> int {
 //  3 | 
 //  4 | for (i = 0; i < 3; i += 1) {
 //    | 
-// error: Error validating: Invalid binary operation: cannot infer type of left operand
-//   -->  loops/header_requires_let_negative.baml:4
-//    | 
-//  3 | 
-//  4 | for (i = 0; i < 3; i += 1) {
-//    | 
 // error: Error validating: Unknown variable i
 //   -->  loops/header_requires_let_negative.baml:4
 //    |