fix alias error incorrectly reported

cli/src/build.rs

@@ -117,6 +117,11 @@ pub fn build_file<'a>(
     report_timing(buf, "Generate LLVM IR", code_gen_timing.code_gen);
     report_timing(buf, "Emit .o file", code_gen_timing.emit_o_file);
 
+    let compilation_end = compilation_start.elapsed().unwrap();
+
+    let size = std::fs::metadata(&app_o_file).unwrap().len();
+
+    if emit_debug_info {
         println!(
             "\n\nCompilation finished! Here's how long each module took to compile:\n\n{}",
             buf
@@ -124,15 +129,12 @@ pub fn build_file<'a>(
 
         println!("\nSuccess! 🎉\n\n\t➡ {}\n", app_o_file.display());
 
-    let compilation_end = compilation_start.elapsed().unwrap();
-
-    let size = std::fs::metadata(&app_o_file).unwrap().len();
-
         println!(
             "Finished compilation and code gen in {} ms\n\nProduced a app.o file of size {:?}\n",
             compilation_end.as_millis(),
             size,
         );
+    }
 
     // Step 2: link the precompiled host and compiled app
     let mut host_input_path = PathBuf::from(cwd);
@@ -144,10 +146,13 @@ pub fn build_file<'a>(
     let rebuild_host_start = SystemTime::now();
     rebuild_host(host_input_path.as_path());
     let rebuild_host_end = rebuild_host_start.elapsed().unwrap();
+
+    if emit_debug_info {
         println!(
             "Finished rebuilding the host in {} ms\n",
             rebuild_host_end.as_millis()
         );
+    }
 
     // TODO try to move as much of this linking as possible to the precompiled
     // host, to minimize the amount of host-application linking required.
@@ -168,7 +173,9 @@ pub fn build_file<'a>(
     });
 
     let link_end = link_start.elapsed().unwrap();
+    if emit_debug_info {
         println!("Finished linking in {} ms\n", link_end.as_millis());
+    }
 
     // Clean up the leftover .o file from the Roc, if possible.
     // (If cleaning it up fails, that's fine. No need to take action.)

compiler/unify/src/unify.rs

@@ -190,7 +190,9 @@ fn unify_alias(
                         problems.extend(unify_pool(subs, pool, *l_var, *r_var));
                     }
 
+                    if problems.is_empty() {
                         problems.extend(merge(subs, &ctx, other_content.clone()));
+                    }
 
                     if problems.is_empty() {
                         problems.extend(unify_pool(subs, pool, real_var, *other_real_var));