Better default assert messages when no message is specified #2122

Author: lerno

releasenotes.md

@@ -2,6 +2,9 @@
 
 ## 0.7.2 Change list
 
+### Changes / improvements
+- Better default assert messages when no message is specified #2122
+
 ### Fixes
 - Assert triggered when casting from `int[2]` to `uint[2]` #2115
 - Assert when a macro with compile time value is discarded, e.g. `foo();` where `foo()` returns an untyped list. #2117

src/compiler/sema_stmts.c

@@ -181,6 +181,15 @@ static inline bool sema_analyse_assert_stmt(SemaContext *context, Ast *statement
 			return true;
 		case COND_MISSING:
 			// If the assert isn't compile time resolvable, we keep the assert.
+			if (!message_expr)
+			{
+				scratch_buffer_clear();
+				scratch_buffer_append("Assert \"");
+				span_to_scratch(expr->span);
+				scratch_buffer_append("\" failed.");
+				message_expr = expr_new_const_string(expr->span, scratch_buffer_copy());
+				statement->assert_stmt.message = exprid(message_expr);
+			}
 			return true;
 	}
 	UNREACHABLE

test/test_suite/assert/assert_default_print.c3t

@@ -0,0 +1,29 @@
+// #target: macos-x64
+// #safe: yes
+module test;
+fn void main()
+{
+	int a = -1;
+	assert(a > 0);
+}
+
+/* #expect: test.ll
+
+@.panic_msg = internal constant [23 x i8] c"Assert \22a > 0\22 failed.\00", align 1
+
+define void @test.main() #0 {
+entry:
+  %a = alloca i32, align 4
+  store i32 -1, ptr %a, align 4
+  %0 = load i32, ptr %a, align 4
+  %gt = icmp sgt i32 %0, 0
+  br i1 %gt, label %assert_ok, label %assert_fail
+
+assert_fail:                                      ; preds = %entry
+  %1 = load ptr, ptr @std.core.builtin.panic, align 8
+  call void %1(ptr @.panic_msg, i64 22, ptr @.file, i64 23, ptr @.func, i64 4, i32 5) #1
+  unreachable
+
+assert_ok:                                        ; preds = %entry
+  ret void
+}