implement lazy values for error union types

closes #3129

3 files changed, 86 insertions, 21 deletions

diff --git a/src/all_types.hpp b/src/all_types.hpp
index 38964d0091..48323e58ad 100644
--- a/src/all_types.hpp
+++ b/src/all_types.hpp
@@ -312,6 +312,7 @@ enum LazyValueId {
     LazyValueIdOptType,
     LazyValueIdSliceType,
     LazyValueIdFnType,
+    LazyValueIdErrUnionType,
 };
 
 struct LazyValue {
@@ -372,6 +373,14 @@ struct LazyValueFnType {
     bool is_generic;
 };
 
+struct LazyValueErrUnionType {
+    LazyValue base;
+
+    IrAnalyze *ira;
+    IrInstruction *err_set_type;
+    IrInstruction *payload_type;
+};
+
 struct ConstExprValue {
     ZigType *type;
     ConstValSpecial special;
diff --git a/src/analyze.cpp b/src/analyze.cpp
index 965bd57e02..9ae7e99547 100644
--- a/src/analyze.cpp
+++ b/src/analyze.cpp
@@ -1015,6 +1015,7 @@ static Error type_val_resolve_zero_bits(CodeGen *g, ConstExprValue *type_val, Zi
         }
         case LazyValueIdOptType:
         case LazyValueIdSliceType:
+        case LazyValueIdErrUnionType:
             *is_zero_bits = false;
             return ErrorNone;
         case LazyValueIdFnType: {
@@ -1040,6 +1041,7 @@ Error type_val_resolve_is_opaque_type(CodeGen *g, ConstExprValue *type_val, bool
         case LazyValueIdPtrType:
         case LazyValueIdFnType:
         case LazyValueIdOptType:
+        case LazyValueIdErrUnionType:
             *is_opaque_type = false;
             return ErrorNone;
     }
@@ -1094,6 +1096,11 @@ static ReqCompTime type_val_resolve_requires_comptime(CodeGen *g, ConstExprValue
             }
             return ReqCompTimeNo;
         }
+        case LazyValueIdErrUnionType: {
+            LazyValueErrUnionType *lazy_err_union_type =
+                reinterpret_cast<LazyValueErrUnionType *>(type_val->data.x_lazy);
+            return type_val_resolve_requires_comptime(g, &lazy_err_union_type->payload_type->value);
+        }
     }
     zig_unreachable();
 }
@@ -1102,10 +1109,8 @@ static Error type_val_resolve_abi_size(CodeGen *g, AstNode *source_node, ConstEx
         size_t *abi_size, size_t *size_in_bits)
 {
     Error err;
-    if (type_val->data.x_lazy->id == LazyValueIdOptType) {
-        if ((err = ir_resolve_lazy(g, source_node, type_val)))
-            return err;
-    }
+
+start_over:
     if (type_val->special != ConstValSpecialLazy) {
         assert(type_val->special == ConstValSpecialStatic);
         ZigType *ty = type_val->data.x_type;
@@ -1129,7 +1134,10 @@ static Error type_val_resolve_abi_size(CodeGen *g, AstNode *source_node, ConstEx
             *size_in_bits = g->builtin_types.entry_usize->size_in_bits;
             return ErrorNone;
         case LazyValueIdOptType:
-            zig_unreachable();
+        case LazyValueIdErrUnionType:
+            if ((err = ir_resolve_lazy(g, source_node, type_val)))
+                return err;
+            goto start_over;
     }
     zig_unreachable();
 }
@@ -1161,6 +1169,19 @@ Error type_val_resolve_abi_align(CodeGen *g, ConstExprValue *type_val, uint32_t
             LazyValueOptType *lazy_opt_type = reinterpret_cast<LazyValueOptType *>(type_val->data.x_lazy);
             return type_val_resolve_abi_align(g, &lazy_opt_type->payload_type->value, abi_align);
         }
+        case LazyValueIdErrUnionType: {
+            LazyValueErrUnionType *lazy_err_union_type =
+                reinterpret_cast<LazyValueErrUnionType *>(type_val->data.x_lazy);
+            uint32_t payload_abi_align;
+            if ((err = type_val_resolve_abi_align(g, &lazy_err_union_type->payload_type->value,
+                            &payload_abi_align)))
+            {
+                return err;
+            }
+            *abi_align = (payload_abi_align > g->err_tag_type->abi_align) ?
+                payload_abi_align : g->err_tag_type->abi_align;
+            return ErrorNone;
+        }
     }
     zig_unreachable();
 }
@@ -1189,6 +1210,18 @@ static OnePossibleValue type_val_resolve_has_one_possible_value(CodeGen *g, Cons
                 return OnePossibleValueNo;
             }
         }
+        case LazyValueIdErrUnionType: {
+            LazyValueErrUnionType *lazy_err_union_type =
+                reinterpret_cast<LazyValueErrUnionType *>(type_val->data.x_lazy);
+            switch (type_val_resolve_has_one_possible_value(g, &lazy_err_union_type->err_set_type->value)) {
+                case OnePossibleValueInvalid:
+                    return OnePossibleValueInvalid;
+                case OnePossibleValueNo:
+                    return OnePossibleValueNo;
+                case OnePossibleValueYes:
+                    return type_val_resolve_has_one_possible_value(g, &lazy_err_union_type->payload_type->value);
+            }
+        }
     }
     zig_unreachable();
 }
diff --git a/src/ir.cpp b/src/ir.cpp
index 15fa4ccbe1..52cf69de82 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -14626,28 +14626,23 @@ static IrInstruction *ir_analyze_instruction_error_return_trace(IrAnalyze *ira,
 static IrInstruction *ir_analyze_instruction_error_union(IrAnalyze *ira,
         IrInstructionErrorUnion *instruction)
 {
-    Error err;
+    IrInstruction *result = ir_const(ira, &instruction->base, ira->codegen->builtin_types.entry_type);
+    result->value.special = ConstValSpecialLazy;
 
-    ZigType *err_set_type = ir_resolve_type(ira, instruction->err_set->child);
-    if (type_is_invalid(err_set_type))
-        return ira->codegen->invalid_instruction;
+    LazyValueErrUnionType *lazy_err_union_type = allocate<LazyValueErrUnionType>(1);
+    lazy_err_union_type->ira = ira;
+    result->value.data.x_lazy = &lazy_err_union_type->base;
+    lazy_err_union_type->base.id = LazyValueIdErrUnionType;
 
-    ZigType *payload_type = ir_resolve_type(ira, instruction->payload->child);
-    if (type_is_invalid(payload_type))
+    lazy_err_union_type->err_set_type = instruction->err_set->child;
+    if (ir_resolve_type_lazy(ira, lazy_err_union_type->err_set_type) == nullptr)
         return ira->codegen->invalid_instruction;
 
-    if (err_set_type->id != ZigTypeIdErrorSet) {
-        ir_add_error(ira, instruction->err_set->child,
-            buf_sprintf("expected error set type, found type '%s'",
-                buf_ptr(&err_set_type->name)));
+    lazy_err_union_type->payload_type = instruction->payload->child;
+    if (ir_resolve_type_lazy(ira, lazy_err_union_type->payload_type) == nullptr)
         return ira->codegen->invalid_instruction;
-    }
 
-    if ((err = type_resolve(ira->codegen, payload_type, ResolveStatusSizeKnown)))
-        return ira->codegen->invalid_instruction;
-    ZigType *result_type = get_error_union_type(ira->codegen, err_set_type, payload_type);
-
-    return ir_const_type(ira, &instruction->base, result_type);
+    return result;
 }
 
 static IrInstruction *ir_analyze_alloca(IrAnalyze *ira, IrInstruction *source_inst, ZigType *var_type,
@@ -25698,6 +25693,34 @@ static Error ir_resolve_lazy_raw(AstNode *source_node, ConstExprValue *val) {
             val->data.x_type = fn_type;
             return ErrorNone;
         }
+        case LazyValueIdErrUnionType: {
+            LazyValueErrUnionType *lazy_err_union_type =
+                reinterpret_cast<LazyValueErrUnionType *>(val->data.x_lazy);
+            IrAnalyze *ira = lazy_err_union_type->ira;
+
+            ZigType *err_set_type = ir_resolve_type(ira, lazy_err_union_type->err_set_type);
+            if (type_is_invalid(err_set_type))
+                return ErrorSemanticAnalyzeFail;
+
+            ZigType *payload_type = ir_resolve_type(ira, lazy_err_union_type->payload_type);
+            if (type_is_invalid(payload_type))
+                return ErrorSemanticAnalyzeFail;
+
+            if (err_set_type->id != ZigTypeIdErrorSet) {
+                ir_add_error(ira, lazy_err_union_type->err_set_type,
+                    buf_sprintf("expected error set type, found type '%s'",
+                        buf_ptr(&err_set_type->name)));
+                return ErrorSemanticAnalyzeFail;
+            }
+
+            if ((err = type_resolve(ira->codegen, payload_type, ResolveStatusSizeKnown)))
+                return ErrorSemanticAnalyzeFail;
+
+            assert(val->type->id == ZigTypeIdMetaType);
+            val->data.x_type = get_error_union_type(ira->codegen, err_set_type, payload_type);
+            val->special = ConstValSpecialStatic;
+            return ErrorNone;
+        }
     }
     zig_unreachable();
 }