Fix too strict assert for calldata string -> bytes conversions

Author: Marenz

Changelog.md

@@ -12,12 +12,13 @@ Compiler Features:
 
 Bugfixes:
  * Antlr Grammar: Allow builtin names in ``yulPath`` to support ``.address`` in function pointers.
+ * Code Generator: Fix ICE when accessing the members of external functions occupying more than two stack slots.
+ * Code Generator: Fix ICE when doing an explicit conversion from ``string calldata`` to ``bytes``.
  * Control Flow Graph: Perform proper virtual lookup for modifiers for uninitialized variable and unreachable code analysis.
  * Immutables: Fix wrong error when the constructor of a base contract uses ``return`` and the parent contract contains immutable variables.
  * IR Generator: Fix IR syntax error when copying storage arrays of structs containing functions.
  * Natspec: Fix ICE when overriding a struct getter with a Natspec-documented return value and the name in the struct is different.
  * TypeChecker: Fix ICE when a constant variable declaration forward references a struct.
- * Code Generator: Fix ICE when accessing the members of external functions occupying more than two stack slots.
 
 
 Solc-Js:

libsolidity/codegen/CompilerUtils.cpp

@@ -1140,7 +1140,10 @@ void CompilerUtils::convertType(
 
 		solAssert(_targetType.category() == Type::Category::Array, "");
 		auto const& targetArrayType = dynamic_cast<ArrayType const&>(_targetType);
-		solAssert(typeOnStack.arrayType().isImplicitlyConvertibleTo(targetArrayType), "");
+		solAssert(
+			typeOnStack.arrayType().isImplicitlyConvertibleTo(targetArrayType) ||
+			(typeOnStack.arrayType().isByteArray() && targetArrayType.isByteArray())
+		);
 		solAssert(
 			typeOnStack.arrayType().dataStoredIn(DataLocation::CallData) &&
 			typeOnStack.arrayType().isDynamicallySized() &&

libsolidity/codegen/YulUtilFunctions.cpp

@@ -3222,7 +3222,10 @@ string YulUtilFunctions::conversionFunction(Type const& _from, Type const& _to)
 		solAssert(_to.category() == Type::Category::Array, "");
 		auto const& targetType = dynamic_cast<ArrayType const&>(_to);
 
-		solAssert(fromType.arrayType().isImplicitlyConvertibleTo(targetType), "");
+		solAssert(
+			fromType.arrayType().isImplicitlyConvertibleTo(targetType) ||
+			(fromType.arrayType().isByteArray() && targetType.isByteArray())
+		);
 		solAssert(
 			fromType.arrayType().dataStoredIn(DataLocation::CallData) &&
 			fromType.arrayType().isDynamicallySized() &&

test/libsolidity/semanticTests/viaYul/conversion/explicit_string_bytes_calldata_cast.sol

@@ -0,0 +1,11 @@
+// Triggered ICE before
+contract C {
+	function f(string calldata data) external pure returns(string memory) {
+		bytes calldata test = bytes(data[:3]);
+		return string(test);
+	}
+}
+// ====
+// compileViaYul: also
+// ----
+// f(string): 0x20, 3, "123" -> 0x20, 3, "123"