Legacy TupleExpression processor is unable to unnest single tuple element

[blitz-1306]

Environment

Any

Scenario

1. Create a Solidity source file sample.sol with following contents:

contract Test {
    function some(uint a, uint b) pure public returns(uint, uint) {
        return ((a, b));
    }

    function verify() public {
        (uint a, uint b) = some(1, 2);

        assert(a == 1);
        assert(b == 2);
    }
}

2. Run following command:

sol-ast-compile sample.sol --tree --compiler-version 0.4.26

Expected behavior

Expected to get short AST tree description.

Current behavior

Got following error:

Error: Expected component of type uint256 but got component of type tuple(uint256,uint256)
    at LegacyTupleExpressionProcessor.extractComponentsFromTypeString (solc-typed-ast/dist/ast/legacy/tuple_expression_processor.js:49:27)
    at LegacyTupleExpressionProcessor.process (solc-typed-ast/dist/ast/legacy/tuple_expression_processor.js:14:20)
    at ASTReader.convert (solc-typed-ast/dist/ast/ast_reader.js:159:32)
    at ASTReader.convertArray (solc-typed-ast/dist/ast/ast_reader.js:174:35)
    at LegacyReturnProcessor.process (solc-typed-ast/dist/ast/legacy/return_processor.js:8:48)
    at ASTReader.convert (solc-typed-ast/dist/ast/ast_reader.js:159:32)
    at ASTReader.convertArray (solc-typed-ast/dist/ast/ast_reader.js:174:35)
    at LegacyBlockProcessor.process (solc-typed-ast/dist/ast/legacy/block_processor.js:8:35)
    at ASTReader.convert (solc-typed-ast/dist/ast/ast_reader.js:159:32)
    at ASTReader.convertArray (solc-typed-ast/dist/ast/ast_reader.js:174:35)

Description

Legacy TupleExpression processor is fragile: it not supports tuple unnesting. When we have a single member in tuple, like ((1)), Solidity unnest it by default to 1. Same applies to nested tuple expressions, like in example above.

Regards.