Merge pull request #14365 from ethereum/declarationFunctionTypeConversions

Disallow conversions between declaration function types.

Changelog.md

@@ -29,6 +29,7 @@ Bugfixes:
  * SMTChecker: Fix false negative when a verification target can be violated only by trusted external call from another public function.
  * SMTChecker: Fix internal error caused by using external identifier to encode member access to functions that take an internal function as a parameter.
  * Standard JSON Interface: Fix an incomplete AST being returned when analysis is interrupted by certain kinds of fatal errors.
+ * Type Checker: Function declaration types referring to different declarations are no longer convertible to each other.
  * 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 ``FullInliner`` step not ignoring code that is not in expression-split form.
  * Yul Optimizer: Fix optimized IR being unnecessarily passed through the Yul optimizer again before bytecode generation.

libsolidity/ast/Types.cpp

@@ -3127,6 +3127,12 @@ BoolResult FunctionType::isImplicitlyConvertibleTo(Type const& _convertTo) const
 	if (convertTo.kind() != kind())
 		return BoolResult::err("Special functions cannot be converted to function types.");
 
+	if (
+		kind() == FunctionType::Kind::Declaration &&
+		m_declaration != convertTo.m_declaration
+	)
+		return BoolResult::err("Function declaration types referring to different functions cannot be converted to each other.");
+
 	if (!equalExcludingStateMutability(convertTo))
 		return false;
 

test/libsolidity/syntaxTests/functionTypes/declaration_type_conversion.sol

@@ -0,0 +1,11 @@
+contract D {
+	function f() external {}
+	function g() external {}
+}
+contract C {
+	function f(bool c) public pure {
+		(c ? D.f : D.g);
+	}
+}
+// ----
+// TypeError 1080: (117-130): True expression's type function D.f() does not match false expression's type function D.g().

test/libsolidity/syntaxTests/functionTypes/declaration_type_conversion_internal_base.sol

@@ -0,0 +1,11 @@
+contract C {
+    function f() internal {}
+    function g() internal {}
+}
+
+contract D is C {
+    function h(bool b) public pure {
+        (b ? C.f : C.g);
+    }
+}
+// ----