Sema: Diagnose 'lazy' variable initializer with effect

This used to crash in SILGen.

Fixes #60128
Fixes #60129

Author: slavapestov

include/swift/AST/DiagnosticsSema.def

@@ -5302,14 +5302,22 @@ ERROR(tryless_throwing_call_in_nonexhaustive_catch,none,
 ERROR(throw_in_nonexhaustive_catch,none,
       "error is not handled because the enclosing catch is not exhaustive", ())
 
+#define EFFECTS_CONTEXT_KIND \
+  "%select{<<ERROR>>|" \
+  "a default argument|" \
+  "a property wrapper initializer|" \
+  "a property initializer|" \
+  "a global variable initializer|" \
+  "a lazy variable initializer|" \
+  "an enum case raw value|" \
+  "a catch pattern|" \
+  "a catch guard expression|" \
+  "a defer body}" \
+
 ERROR(throwing_op_in_illegal_context,none,
-      "%1 can throw, but errors cannot be thrown out of "
-      "%select{<<ERROR>>|a default argument|a property wrapper initializer|a property initializer|a global variable initializer|an enum case raw value|a catch pattern|a catch guard expression|a defer body}0",
-      (unsigned, StringRef))
+      "%1 can throw, but errors cannot be thrown out of " EFFECTS_CONTEXT_KIND "0", (unsigned, StringRef))
 ERROR(throw_in_illegal_context,none,
-      "errors cannot be thrown out of "
-      "%select{<<ERROR>>|a default argument|a property wrapper initializer|a property initializer|a global variable initializer|an enum case raw value|a catch pattern|a catch guard expression|a defer body}0",
-      (unsigned))
+      "errors cannot be thrown out of " EFFECTS_CONTEXT_KIND "0", (unsigned))
 
 ERROR(throwing_operator_without_try,none,
       "operator can throw but expression is not marked with 'try'", ())
@@ -5405,17 +5413,6 @@ ERROR(async_let_no_variables,none,
 NOTE(async_let_without_await,none,
       "reference to async let %0 is 'async'", (const ValueDecl *))
 
-#define EFFECTS_CONTEXT_KIND \
-  "%select{<<ERROR>>|" \
-  "a default argument|" \
-  "a property wrapper initializer|" \
-  "a property initializer|" \
-  "a global variable initializer|" \
-  "an enum case raw value|" \
-  "a catch pattern|" \
-  "a catch guard expression|" \
-  "a defer body}" \
-
 ERROR(async_call_in_illegal_context,none,
       "'async' call cannot occur in " EFFECTS_CONTEXT_KIND "0",
       (unsigned))

lib/Sema/TypeCheckEffects.cpp

@@ -509,6 +509,10 @@ template <class Impl>
 class EffectsHandlingWalker : public ASTWalker {
   Impl &asImpl() { return *static_cast<Impl*>(this); }
 public:
+  LazyInitializerWalking getLazyInitializerWalkingBehavior() override {
+    return LazyInitializerWalking::InAccessor;
+  }
+
   /// Only look at the expansions for effects checking.
   MacroWalking getMacroWalkingBehavior() const override {
     return MacroWalking::Expansion;
@@ -940,7 +944,7 @@ class Classification {
                                   ConditionalEffectKind conditionalKind,
                                   PotentialEffectReason reason) {
     Classification result;
-    if (!thrownError || isNeverThrownError(thrownError))
+    if (isNeverThrownError(thrownError))
       return result;
 
     assert(!thrownError->hasError());
@@ -2086,6 +2090,9 @@ class Context {
     /// The initializer for a global variable.
     GlobalVarInitializer,
 
+    /// The initializer for a `lazy` variable.
+    LazyVarInitializer,
+
     /// The initializer for an enum element.
     EnumElementInitializer,
 
@@ -2101,8 +2108,12 @@ class Context {
 
 private:
   static Context getContextForPatternBinding(PatternBindingDecl *pbd) {
+    auto *var = pbd->getSingleVar();
+
     if (!pbd->isStatic() && pbd->getDeclContext()->isTypeContext()) {
       return Context(Kind::IVarInitializer, pbd->getDeclContext());
+    } else if (var && var->getAttrs().hasAttribute<LazyAttr>()) {
+      return Context(Kind::LazyVarInitializer, pbd->getDeclContext());
     } else {
       return Context(Kind::GlobalVarInitializer, pbd->getDeclContext());
     }
@@ -2520,6 +2531,7 @@ class Context {
 
     case Kind::EnumElementInitializer:
     case Kind::GlobalVarInitializer:
+    case Kind::LazyVarInitializer:
     case Kind::IVarInitializer:
     case Kind::DefaultArgument:
     case Kind::PropertyWrapper:
@@ -2556,6 +2568,7 @@ class Context {
 
     case Kind::EnumElementInitializer:
     case Kind::GlobalVarInitializer:
+    case Kind::LazyVarInitializer:
     case Kind::IVarInitializer:
     case Kind::DefaultArgument:
     case Kind::PropertyWrapper:
@@ -2582,6 +2595,7 @@ class Context {
 
     case Kind::EnumElementInitializer:
     case Kind::GlobalVarInitializer:
+    case Kind::LazyVarInitializer:
     case Kind::IVarInitializer:
     case Kind::DefaultArgument:
     case Kind::PropertyWrapper:
@@ -2691,6 +2705,7 @@ class Context {
 
     case Kind::EnumElementInitializer:
     case Kind::GlobalVarInitializer:
+    case Kind::LazyVarInitializer:
     case Kind::IVarInitializer:
     case Kind::DefaultArgument:
     case Kind::PropertyWrapper:

test/decl/var/lazy_properties_effects.swift

@@ -0,0 +1,17 @@
+// RUN: %target-typecheck-verify-swift -disable-availability-checking
+
+// We could make this work by having `lazy` synthesize an effectful
+// getter, but for now let's reject it instead of crashing.
+
+func throwsFunc() throws -> Int { return 3 }
+func asyncFunc() async -> Int { return 3 }
+
+func localLazyWithEffects() {
+  lazy var x = try throwsFunc() // expected-error {{call can throw, but errors cannot be thrown out of a lazy variable initializer}}
+  lazy var y = await asyncFunc() // expected-error {{'async' call cannot occur in a lazy variable initializer}}
+}
+
+struct InstanceLazyWithEffects {
+  lazy var x = try throwsFunc() // expected-error {{call can throw, but errors cannot be thrown out of a property initializer}}
+  lazy var y = await asyncFunc() // expected-error {{'async' call cannot occur in a property initializer}}
+}