Add typechecking for if expressions

2 files changed, 50 insertions, 10 deletions

diff --git a/src/main.c b/src/main.c
index a66a40c..df2f687 100644
--- a/src/main.c
+++ b/src/main.c
@@ -253,6 +253,36 @@ type_inference(Analyzer *a, Node *node, TypeScope *scope) {
             }
             return node->type;
         } break;
+        case NODE_IF: {
+            Type type = type_inference(a, node->cond_if, scope);
+            if (!str_eq(type, cstr("bool"))) {
+                emit_semantic_error(
+                    a, node->cond_if,
+                    cstr("non boolean expression on if condition"));
+                return cstr("");
+            }
+            if (node->cond_expr->kind == NODE_BLOCK) {
+                node->type = type_inference(a, node->cond_expr, scope);
+            } else {
+                TypeScope *next = typescope_alloc(a, scope);
+                node->type = type_inference(a, node->cond_expr, next);
+            }
+            if (node->cond_else) {
+                Type else_type;
+                if (node->cond_else->kind == NODE_BLOCK) {
+                    else_type = type_inference(a, node->cond_else, scope);
+                } else {
+                    TypeScope *next = typescope_alloc(a, scope);
+                    else_type = type_inference(a, node->cond_else, next);
+                }
+                if (!str_eq(node->type, else_type)) {
+                    emit_semantic_error(
+                        a, node,
+                        cstr("mismatch types for if/else branches"));
+                    return cstr("");
+                }
+            }
+        } break;
         case NODE_TRUE:
         case NODE_FALSE: {
             node->type = cstr("bool");
diff --git a/tests/semantics.bad b/tests/semantics.bad
index 158cec6..c316a3c 100644
--- a/tests/semantics.bad
+++ b/tests/semantics.bad
@@ -1,15 +1,25 @@
 ; let a:f32 = (1.0 + 2.0 * 2.0) / 2.0
 
-let annotated:int = (1 + 2 * 2) / 2
-let numbers = 1
-let symbols = numbers
-let arith = 1 + 2 * 4
-let cmp = 1 <= 2
-let logic = !true && false || (1 <= 2)
-let bits = 0xff & 0b00001111
-let block = {
-    let a = 1 + 2
-    a + 3
+; let annotated:int = (1 + 2 * 2) / 2
+; let numbers = 1
+; let symbols = numbers
+; let arith = 1 + 2 * 4
+; let cmp = 1 <= 2
+; let logic = !true && false || (1 <= 2)
+; let bits = 0xff & 0b00001111
+; let block = {
+;     let a = 1 + 2
+;     a + 3
+; }
+
+let maybe = if (1 == 2) {
+    32
+} else {
+    44
+}
+
+let single = if (true) {
+    123
 }
 
 ; enum test {