Fix #8450. Prevented internal compiler errors when assigning nested tuples.

Changelog.md

@@ -10,6 +10,7 @@ Compiler Features:
 Bugfixes:
  * Inline Assembly: Fix internal error when accessing invalid constant variables.
  * Reference Resolver: Fix internal error when accessing invalid struct members.
+ * Type Checker: Fix internal errors when assigning nested tuples.
  * Inheritance: Allow public state variables to override functions with dynamic memory types in their return values.
  * JSON AST: Always add pointer suffix for memory reference types.
 

libsolidity/analysis/TypeChecker.cpp

@@ -1317,11 +1317,11 @@ void TypeChecker::checkExpressionAssignment(Type const& _type, Expression const&
 	if (auto const* tupleExpression = dynamic_cast<TupleExpression const*>(&_expression))
 	{
 		auto const* tupleType = dynamic_cast<TupleType const*>(&_type);
-		auto const& types = tupleType ? tupleType->components() : vector<TypePointer> { &_type };
+		auto const& types = tupleType && tupleExpression->components().size() > 1 ? tupleType->components() : vector<TypePointer> { &_type };
 
 		solAssert(
 			tupleExpression->components().size() == types.size() || m_errorReporter.hasErrors(),
-			"Array sizes don't match or no errors generated."
+			"Array sizes don't match and no errors generated."
 		);
 
 		for (size_t i = 0; i < min(tupleExpression->components().size(), types.size()); i++)

test/libsolidity/semanticTests/types/tuple_in_tuple.sol

@@ -0,0 +1,24 @@
+contract test {
+    function f0() public returns(int, bool) {
+        int a;
+        bool b;
+        ((a, b)) = (2, true);
+        return (a, b);
+    }
+    function f1() public returns(int) {
+        int a;
+        (((a, ), )) = ((1, 2) ,3);
+        return a;
+    }
+    function f2() public returns(int) {
+        int a;
+        (((, a),)) = ((1, 2), 3);
+        return a;
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// f0() -> 2, true
+// f1() -> 1
+// f2() -> 2

test/libsolidity/syntaxTests/tupleAssignments/tuple_in_tuple_long.sol

@@ -0,0 +1,12 @@
+contract C {
+  function f() {
+    (((((((((((,2),)),)),),))=4)));
+  }
+}
+// ----
+// SyntaxError: (15-69): No visibility specified. Did you intend to add "public"?
+// TypeError: (46-47): Expression has to be an lvalue.
+// TypeError: (60-61): Type int_const 4 is not implicitly convertible to expected type tuple(tuple(tuple(tuple(tuple(,int_const 2),),),),).
+// TypeError: (37-61): Tuple component cannot be empty.
+// TypeError: (36-62): Tuple component cannot be empty.
+// TypeError: (35-63): Tuple component cannot be empty.

test/libsolidity/syntaxTests/tupleAssignments/tuple_in_tuple_short.sol

@@ -0,0 +1,6 @@
+contract C {
+  function f() public pure {
+    int a;
+    (((a,),)) = ((1,2),3);
+  }
+}