From 2f1fa9ae77e654a5704e05776440e45fabbde19b Mon Sep 17 00:00:00 2001
From: Emilio Almansi <ealmansi@gmail.com>
Date: Sun, 4 Jun 2023 12:58:59 +0700
Subject: [PATCH] Fix non-constant event and error selectors

---
 Changelog.md                                  |  1 +
 libsolidity/analysis/TypeChecker.cpp          | 23 +++++++++++++++++++
 .../constant_from_error_selector.sol          | 10 ++++++++
 .../constant_from_event_selector.sol          | 10 ++++++++
 .../constant_from_function_selector.sol       |  9 ++++++++
 5 files changed, 53 insertions(+)
 create mode 100644 test/libsolidity/syntaxTests/constants/constant_from_error_selector.sol
 create mode 100644 test/libsolidity/syntaxTests/constants/constant_from_event_selector.sol
 create mode 100644 test/libsolidity/syntaxTests/constants/constant_from_function_selector.sol

diff --git a/Changelog.md b/Changelog.md
index aac8ab8b2..8cd329408 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -21,6 +21,7 @@ Bugfixes:
  * SMTChecker: Fix false negative when a verification target can be violated only by trusted external call from another public function.
  * Yul Optimizer: Ensure that the assignment of memory slots for variables moved to memory does not depend on AST IDs that may depend on whether additional files are included during compilation.
  * Yul Optimizer: Fix optimized IR being unnecessarily passed through the Yul optimizer again before bytecode generation.
+ * TypeChecker: Fix non-constant event and error selectors.
 
 AST Changes:
  * AST: Add the ``experimentalSolidity`` field to the ``SourceUnit`` nodes, which indicate whether the experimental parsing mode has been enabled via ``pragma experimental solidity``.
diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index e7721fd9e..43c3eb191 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -3358,6 +3358,29 @@ bool TypeChecker::visit(MemberAccess const& _memberAccess)
 
 			annotation.isPure = isPure;
 		}
+	if (
+		auto const* functionType = dynamic_cast<FunctionType const*>(exprType);
+		!annotation.isPure.set() &&
+		functionType &&
+		functionType->kind() == FunctionType::Kind::Event &&
+		functionType->hasDeclaration() &&
+		memberName == "selector"
+	)
+		if (
+			auto const* eventDefinition = dynamic_cast<EventDefinition const*>(&functionType->declaration());
+			eventDefinition &&
+			!eventDefinition->isAnonymous()
+		)
+			annotation.isPure = true;
+	if (
+		auto const* functionType = dynamic_cast<FunctionType const*>(exprType);
+		!annotation.isPure.set() &&
+		functionType &&
+		functionType->kind() == FunctionType::Kind::Error &&
+		functionType->hasDeclaration() &&
+		memberName == "selector"
+	)
+		annotation.isPure = true;
 	if (
 		auto const* varDecl = dynamic_cast<VariableDeclaration const*>(annotation.referencedDeclaration);
 		!annotation.isPure.set() &&
diff --git a/test/libsolidity/syntaxTests/constants/constant_from_error_selector.sol b/test/libsolidity/syntaxTests/constants/constant_from_error_selector.sol
new file mode 100644
index 000000000..b120e3045
--- /dev/null
+++ b/test/libsolidity/syntaxTests/constants/constant_from_error_selector.sol
@@ -0,0 +1,10 @@
+interface I {
+    error Er1();
+}
+contract C {
+    function f() external {}
+    error Er2();
+    bytes4 constant errorSelector1 = I.Er1.selector;
+    bytes4 constant errorSelector2 = Er2.selector;
+}
+// ----
diff --git a/test/libsolidity/syntaxTests/constants/constant_from_event_selector.sol b/test/libsolidity/syntaxTests/constants/constant_from_event_selector.sol
new file mode 100644
index 000000000..4a3898989
--- /dev/null
+++ b/test/libsolidity/syntaxTests/constants/constant_from_event_selector.sol
@@ -0,0 +1,10 @@
+interface I {
+    event Ev1();
+}
+contract C {
+    function f() external {}
+    event Ev2();
+    bytes32 constant eventSelector1 = I.Ev1.selector;
+    bytes32 constant eventSelector2 = Ev2.selector;
+}
+// ----
diff --git a/test/libsolidity/syntaxTests/constants/constant_from_function_selector.sol b/test/libsolidity/syntaxTests/constants/constant_from_function_selector.sol
new file mode 100644
index 000000000..8acc25388
--- /dev/null
+++ b/test/libsolidity/syntaxTests/constants/constant_from_function_selector.sol
@@ -0,0 +1,9 @@
+interface I {
+    function f() external;
+}
+contract C {
+    function f() external {}
+    bytes4 constant functionSelector1 = I.f.selector;
+    bytes4 constant functionSelector2 = this.f.selector;
+}
+// ----