From 2f5d1ec5006ccae81f6de80233fa7800237779e2 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Mon, 19 Nov 2018 11:22:57 -0500
Subject: [PATCH] improve error message when wrong type returned

closes #1650
---
 src/ir.cpp              | 8 +++++++-
 test/compile_errors.zig | 1 +
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/ir.cpp b/src/ir.cpp
index 55f17b811..03389a232 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -34,6 +34,7 @@ struct IrAnalyze {
     size_t old_bb_index;
     size_t instruction_index;
     ZigType *explicit_return_type;
+    AstNode *explicit_return_type_source_node;
     ZigList<IrInstruction *> src_implicit_return_type_list;
     IrBasicBlock *const_predecessor_bb;
 };
@@ -11162,8 +11163,12 @@ static IrInstruction *ir_analyze_instruction_return(IrAnalyze *ira, IrInstructio
         return ir_unreach_error(ira);
 
     IrInstruction *casted_value = ir_implicit_cast(ira, value, ira->explicit_return_type);
-    if (type_is_invalid(casted_value->value.type))
+    if (type_is_invalid(casted_value->value.type) && ira->explicit_return_type_source_node != nullptr) {
+        ErrorMsg *msg = ira->codegen->errors.last();
+        add_error_note(ira->codegen, msg, ira->explicit_return_type_source_node,
+            buf_sprintf("return type declared here"));
         return ir_unreach_error(ira);
+    }
 
     if (casted_value->value.special == ConstValSpecialRuntime &&
         casted_value->value.type->id == ZigTypeIdPointer &&
@@ -21213,6 +21218,7 @@ ZigType *ir_analyze(CodeGen *codegen, IrExecutable *old_exec, IrExecutable *new_
     ZigFn *fn_entry = exec_fn_entry(old_exec);
     bool is_async = fn_entry != nullptr && fn_entry->type_entry->data.fn.fn_type_id.cc == CallingConventionAsync;
     ira->explicit_return_type = is_async ? get_promise_type(codegen, expected_type) : expected_type;
+    ira->explicit_return_type_source_node = expected_type_source_node;
 
     ira->old_irb.codegen = codegen;
     ira->old_irb.exec = old_exec;
diff --git a/test/compile_errors.zig b/test/compile_errors.zig
index 45bd6cb40..16690daf2 100644
--- a/test/compile_errors.zig
+++ b/test/compile_errors.zig
@@ -3219,6 +3219,7 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
         \\fn something() anyerror!void { }
     ,
         ".tmp_source.zig:2:5: error: expected type 'void', found 'anyerror'",
+        ".tmp_source.zig:1:15: note: return type declared here",
     );
 
     cases.add(