/*

 * pass_validation_linking.rs

 *

 * The pass that will validate properties of the AST statements (one is not

 * allowed to nest synchronous statements, instantiating components occurs in

 * the right places, etc.) and expressions (assignments may not occur in

 * arbitrary expressions).

 *

 * Furthermore, this pass will also perform "linking", in the sense of: some AST

 * nodes have something to do with one another, so we link them up in this pass

 * (e.g. setting the parents of expressions, linking the control flow statements

 * like `continue` and `break` up to the respective loop statement, etc.).

 *

 * There are several "confusing" parts about this pass:

 *

 * Setting expression parents: this is the simplest one. The pass struct acts

 * like a little state machine. When visiting an expression it will set the

 * "parent expression" field of the pass to itself, then visit its child. The

 * child will look at this "parent expression" field to determine its parent.

 *

 * Setting the `next` statement: the AST is a tree, but during execution we walk

 * a linear path through all statements. So where appropriate a statement may

 * set the "previous statement" field of the pass to itself. When visiting the

 * subsequent statement it will check this "previous statement", and if set, it

 * will link this previous statement up to itself. Not every statement has a

 * previous statement. Hence there are two patterns that occur: assigning the

 * `next` value, then clearing the "previous statement" field. And assigning the

 * `next` value, and then putting the current statement's ID in the "previous

 * statement" field. Because it is so common, this file contain two macros that

 * perform that operation.

 *

 * To make storing types for polymorphic procedures simpler and more efficient,

 * we assign to each expression in the procedure a unique ID. This is what the

 * "next expression index" field achieves. Each expression simply takes the

 * current value, and then increments this counter.

 */

use crate::collections::{ScopedBuffer};

use crate::protocol::ast::*;

use crate::protocol::input_source::*;

use crate::protocol::parser::symbol_table::*;

use crate::protocol::parser::type_table::*;

use super::visitor::{

    BUFFER_INIT_CAPACITY,

    Ctx,

    Visitor,

    VisitorResult

};

use crate::protocol::parser::ModuleCompilationPhase;

#[derive(PartialEq, Eq)]

enum DefinitionType {

    Primitive(ComponentDefinitionId),

    Composite(ComponentDefinitionId),

    Function(FunctionDefinitionId)

}

impl DefinitionType {

    fn is_primitive(&self) -> bool { if let Self::Primitive(_) = self { true } else { false } }

    fn is_composite(&self) -> bool { if let Self::Composite(_) = self { true } else { false } }

    fn is_function(&self) -> bool { if let Self::Function(_) = self { true } else { false } }

    fn definition_id(&self) -> DefinitionId {

        match self {

            DefinitionType::Primitive(v) => v.upcast(),

            DefinitionType::Composite(v) => v.upcast(),

            DefinitionType::Function(v) => v.upcast(),

        }

    }

}

/// This particular visitor will go through the entire AST in a recursive manner

/// and check if all statements and expressions are legal (e.g. no "return"

/// statements in component definitions), and will link certain AST nodes to

/// their appropriate targets (e.g. goto statements, or function calls).

///

/// This visitor will not perform control-flow analysis (e.g. making sure that

/// each function actually returns) and will also not perform type checking. So

/// the linking of function calls and component instantiations will be checked

/// and linked to the appropriate definitions, but the return types and/or

/// arguments will not be checked for validity.

pub(crate) struct PassValidationLinking {

    // Traversal state, all valid IDs if inside a certain AST element. Otherwise

    // `id.is_invalid()` returns true.

    in_sync: SynchronousStatementId,

    in_while: WhileStatementId, // to resolve labeled continue/break

    in_select_guard: SelectStatementId, // for detection/rejection of builtin calls

    in_select_arm: u32,

    in_test_expr: StatementId, // wrapping if/while stmt id

    in_binding_expr: BindingExpressionId, // to resolve variable expressions

    in_binding_expr_lhs: bool,

    // Traversal state, current scope (which can be used to find the parent

    // scope) and the definition variant we are considering.

    cur_scope: Scope,

    def_type: DefinitionType,

    // "Trailing" traversal state, set be child/prev stmt/expr used by next one

    prev_stmt: StatementId,

    expr_parent: ExpressionParent,

    // Set by parent to indicate that child expression must be assignable. The

    // child will throw an error if it is not assignable. The stored span is

    // used for the error's position

    must_be_assignable: Option<InputSpan>,

    // Keeping track of relative positions and unique IDs.

    relative_pos_in_block: i32, // of statements: to determine when variables are visible

    next_expr_index: i32, // to arrive at a unique ID for all expressions within a definition

    // Various temporary buffers for traversal. Essentially working around

    // Rust's borrowing rules since it cannot understand we're modifying AST

    // members but not the AST container.

    variable_buffer: ScopedBuffer<VariableId>,

    definition_buffer: ScopedBuffer<DefinitionId>,

    statement_buffer: ScopedBuffer<StatementId>,

    expression_buffer: ScopedBuffer<ExpressionId>,

}

impl PassValidationLinking {

    pub(crate) fn new() -> Self {

        Self{

            in_sync: SynchronousStatementId::new_invalid(),

            in_while: WhileStatementId::new_invalid(),

            in_select_guard: SelectStatementId::new_invalid(),

            in_select_arm: 0,

            in_test_expr: StatementId::new_invalid(),

            in_binding_expr: BindingExpressionId::new_invalid(),

            in_binding_expr_lhs: false,

            cur_scope: Scope::Definition(DefinitionId::new_invalid()),

            prev_stmt: StatementId::new_invalid(),

            expr_parent: ExpressionParent::None,

            def_type: DefinitionType::Function(FunctionDefinitionId::new_invalid()),

            must_be_assignable: None,

            relative_pos_in_block: 0,

            next_expr_index: 0,

            variable_buffer: ScopedBuffer::with_capacity(128),

            definition_buffer: ScopedBuffer::with_capacity(128),

            statement_buffer: ScopedBuffer::with_capacity(BUFFER_INIT_CAPACITY),

            expression_buffer: ScopedBuffer::with_capacity(BUFFER_INIT_CAPACITY),

        }

    }

    fn reset_state(&mut self) {

        self.in_sync = SynchronousStatementId::new_invalid();

        self.in_while = WhileStatementId::new_invalid();

        self.in_test_expr = StatementId::new_invalid();

        self.in_binding_expr = BindingExpressionId::new_invalid();

        self.in_binding_expr_lhs = false;

        self.cur_scope = Scope::Definition(DefinitionId::new_invalid());

        self.def_type = DefinitionType::Function(FunctionDefinitionId::new_invalid());

        self.prev_stmt = StatementId::new_invalid();

        self.expr_parent = ExpressionParent::None;

        self.must_be_assignable = None;

        self.relative_pos_in_block = 0;

        self.next_expr_index = 0

    }

}

macro_rules! assign_then_erase_next_stmt {

    ($self:ident, $ctx:ident, $stmt_id:expr) => {

        if !$self.prev_stmt.is_invalid() {

            $ctx.heap[$self.prev_stmt].link_next($stmt_id);

            $self.prev_stmt = StatementId::new_invalid();

        }

    }

}

macro_rules! assign_and_replace_next_stmt {

    ($self:ident, $ctx:ident, $stmt_id:expr) => {

        if !$self.prev_stmt.is_invalid() {

            $ctx.heap[$self.prev_stmt].link_next($stmt_id);

        }

        $self.prev_stmt = $stmt_id;

    }

}

impl Visitor for PassValidationLinking {

    fn visit_module(&mut self, ctx: &mut Ctx) -> VisitorResult {

        debug_assert_eq!(ctx.module().phase, ModuleCompilationPhase::TypesAddedToTable);

        let root = &ctx.heap[ctx.module().root_id];

        let section = self.definition_buffer.start_section_initialized(&root.definitions);

        for definition_id in section.iter_copied() {

            self.visit_definition(ctx, definition_id)?;

        }

        section.forget();

        ctx.module_mut().phase = ModuleCompilationPhase::ValidatedAndLinked;

        Ok(())

    }

    //--------------------------------------------------------------------------

    // Definition visitors

    //--------------------------------------------------------------------------

    fn visit_component_definition(&mut self, ctx: &mut Ctx, id: ComponentDefinitionId) -> VisitorResult {

        self.reset_state();

        self.def_type = match &ctx.heap[id].variant {

            ComponentVariant::Primitive => DefinitionType::Primitive(id),

            ComponentVariant::Composite => DefinitionType::Composite(id),

        };

        self.cur_scope = Scope::Definition(id.upcast());

        self.expr_parent = ExpressionParent::None;

        // Visit parameters and assign a unique scope ID

        let definition = &ctx.heap[id];

        let body_id = definition.body;

        let section = self.variable_buffer.start_section_initialized(&definition.parameters);

        for variable_idx in 0..section.len() {

            let variable_id = section[variable_idx];

            let variable = &mut ctx.heap[variable_id];

            variable.unique_id_in_scope = variable_idx as i32;

        }

        section.forget();

        // Visit statements in component body

        self.visit_block_stmt(ctx, body_id)?;

        // Assign total number of expressions and assign an in-block unique ID

        // to each of the locals in the procedure.

        ctx.heap[id].num_expressions_in_body = self.next_expr_index;

        self.visit_definition_and_assign_local_ids(ctx, id.upcast());

        Ok(())

    }

    fn visit_function_definition(&mut self, ctx: &mut Ctx, id: FunctionDefinitionId) -> VisitorResult {

        self.reset_state();

        // Set internal statement indices

        self.def_type = DefinitionType::Function(id);

        self.cur_scope = Scope::Definition(id.upcast());

        self.expr_parent = ExpressionParent::None;

        // Visit parameters and assign a unique scope ID

        let definition = &ctx.heap[id];

        let body_id = definition.body;

        let section = self.variable_buffer.start_section_initialized(&definition.parameters);

        for variable_idx in 0..section.len() {

            let variable_id = section[variable_idx];

            let variable = &mut ctx.heap[variable_id];

            variable.unique_id_in_scope = variable_idx as i32;

        }

        section.forget();

        // Visit statements in function body

        self.visit_block_stmt(ctx, body_id)?;

        // Assign total number of expressions and assign an in-block unique ID

        // to each of the locals in the procedure.

        ctx.heap[id].num_expressions_in_body = self.next_expr_index;

        self.visit_definition_and_assign_local_ids(ctx, id.upcast());

        Ok(())

    }

    //--------------------------------------------------------------------------

    // Statement visitors

    //--------------------------------------------------------------------------

    fn visit_block_stmt(&mut self, ctx: &mut Ctx, id: BlockStatementId) -> VisitorResult {

        self.visit_block_stmt_with_hint(ctx, id, None)

    }

    fn visit_local_memory_stmt(&mut self, ctx: &mut Ctx, id: MemoryStatementId) -> VisitorResult {

        let stmt = &ctx.heap[id];

        let expr_id = stmt.initial_expr;

        assign_and_replace_next_stmt!(self, ctx, id.upcast().upcast());

        debug_assert_eq!(self.expr_parent, ExpressionParent::None);

        self.expr_parent = ExpressionParent::Memory(id);

        self.visit_assignment_expr(ctx, expr_id)?;

        self.expr_parent = ExpressionParent::None;

        Ok(())

    }

    fn visit_local_channel_stmt(&mut self, ctx: &mut Ctx, id: ChannelStatementId) -> VisitorResult {

        assign_and_replace_next_stmt!(self, ctx, id.upcast().upcast());

        Ok(())

    }

    fn visit_labeled_stmt(&mut self, ctx: &mut Ctx, id: LabeledStatementId) -> VisitorResult {

        let body_id = ctx.heap[id].body;

        self.visit_stmt(ctx, body_id)?;

        Ok(())

    }

    fn visit_if_stmt(&mut self, ctx: &mut Ctx, id: IfStatementId) -> VisitorResult {

        let if_stmt = &ctx.heap[id];

        let end_if_id = if_stmt.end_if;

        let test_expr_id = if_stmt.test;

        let true_stmt_id = if_stmt.true_body;

        let false_stmt_id = if_stmt.false_body;

        // Visit test expression

        debug_assert_eq!(self.expr_parent, ExpressionParent::None);

        debug_assert!(self.in_test_expr.is_invalid());

        self.in_test_expr = id.upcast();

        self.expr_parent = ExpressionParent::If(id);

        self.visit_expr(ctx, test_expr_id)?;

        self.in_test_expr = StatementId::new_invalid();

        self.expr_parent = ExpressionParent::None;

        // Visit true and false branch. Executor chooses next statement based on

        // test expression, not on if-statement itself. Hence the if statement

        // does not have a static subsequent statement.

        assign_then_erase_next_stmt!(self, ctx, id.upcast());

        self.visit_block_stmt(ctx, true_stmt_id)?;

        assign_then_erase_next_stmt!(self, ctx, end_if_id.upcast());

        if let Some(false_id) = false_stmt_id {

            self.visit_block_stmt(ctx, false_id)?;

            assign_then_erase_next_stmt!(self, ctx, end_if_id.upcast());

        }

        self.prev_stmt = end_if_id.upcast();

        Ok(())

    }

    fn visit_while_stmt(&mut self, ctx: &mut Ctx, id: WhileStatementId) -> VisitorResult {

        let stmt = &ctx.heap[id];

        let end_while_id = stmt.end_while;

        let test_expr_id = stmt.test;

        let body_stmt_id = stmt.body;

        let old_while = self.in_while;

        self.in_while = id;

        // Visit test expression

        debug_assert_eq!(self.expr_parent, ExpressionParent::None);

        debug_assert!(self.in_test_expr.is_invalid());

        self.in_test_expr = id.upcast();

        self.expr_parent = ExpressionParent::While(id);

        self.visit_expr(ctx, test_expr_id)?;

        self.in_test_expr = StatementId::new_invalid();

        // Link up to body statement

        assign_then_erase_next_stmt!(self, ctx, id.upcast());

        self.expr_parent = ExpressionParent::None;

        self.visit_block_stmt(ctx, body_stmt_id)?;

        self.in_while = old_while;

        // Link final entry in while's block statement back to the while. The

        // executor will go to the end-while statement if the test expression

        // is false, so put that in as the new previous stmt

        assign_then_erase_next_stmt!(self, ctx, id.upcast());

        self.prev_stmt = end_while_id.upcast();

        Ok(())

    }

    fn visit_break_stmt(&mut self, ctx: &mut Ctx, id: BreakStatementId) -> VisitorResult {

        // Resolve break target

        let target_end_while = {

            let stmt = &ctx.heap[id];

            let target_while_id = self.resolve_break_or_continue_target(ctx, stmt.span, &stmt.label)?;

            let target_while = &ctx.heap[target_while_id];

            debug_assert!(!target_while.end_while.is_invalid());

            target_while.end_while

        };

        assign_then_erase_next_stmt!(self, ctx, id.upcast());

        let stmt = &mut ctx.heap[id];

        stmt.target = Some(target_end_while);

        Ok(())

    }

    fn visit_continue_stmt(&mut self, ctx: &mut Ctx, id: ContinueStatementId) -> VisitorResult {

        // Resolve continue target

        let target_while_id = {

            let stmt = &ctx.heap[id];

            self.resolve_break_or_continue_target(ctx, stmt.span, &stmt.label)?

        };

        assign_then_erase_next_stmt!(self, ctx, id.upcast());

        let stmt = &mut ctx.heap[id];

        stmt.target = Some(target_while_id);

        Ok(())

    }

    fn visit_synchronous_stmt(&mut self, ctx: &mut Ctx, id: SynchronousStatementId) -> VisitorResult {

        // Check for validity of synchronous statement

        let sync_stmt = &ctx.heap[id];

        let end_sync_id = sync_stmt.end_sync;

        let cur_sync_span = sync_stmt.span;

        if !self.in_sync.is_invalid() {

            // Nested synchronous statement

            let old_sync_span = ctx.heap[self.in_sync].span;

            return Err(ParseError::new_error_str_at_span(

                &ctx.module().source, cur_sync_span, "Illegal nested synchronous statement"

            ).with_info_str_at_span(

                &ctx.module().source, old_sync_span, "It is nested in this synchronous statement"

            ));

        }

        if !self.def_type.is_primitive() {

            return Err(ParseError::new_error_str_at_span(

                &ctx.module().source, cur_sync_span,

                "synchronous statements may only be used in primitive components"

            ));

        }

        // Synchronous statement implicitly moves to its block

        assign_then_erase_next_stmt!(self, ctx, id.upcast());

        let sync_body = ctx.heap[id].body;

        debug_assert!(self.in_sync.is_invalid());

        self.in_sync = id;

        self.visit_block_stmt_with_hint(ctx, sync_body, Some(id))?;

        assign_and_replace_next_stmt!(self, ctx, end_sync_id.upcast());

        self.in_sync = SynchronousStatementId::new_invalid();

        Ok(())

    }

    fn visit_fork_stmt(&mut self, ctx: &mut Ctx, id: ForkStatementId) -> VisitorResult {

        let fork_stmt = &ctx.heap[id];

        let end_fork_id = fork_stmt.end_fork;

        let left_body_id = fork_stmt.left_body;

        let right_body_id = fork_stmt.right_body;

        // Fork statements may only occur inside sync blocks

        if self.in_sync.is_invalid() {

            return Err(ParseError::new_error_str_at_span(

                &ctx.module().source, fork_stmt.span,

                "Forking may only occur inside sync blocks"

            ));

        }

        // Visit the respective bodies. Like the if statement, a fork statement

        // does not have a single static subsequent statement. It forks and then

        // each fork has a different next statement.

        assign_then_erase_next_stmt!(self, ctx, id.upcast());

        self.visit_block_stmt(ctx, left_body_id)?;

        assign_then_erase_next_stmt!(self, ctx, end_fork_id.upcast());

        if let Some(right_body_id) = right_body_id {

            self.visit_block_stmt(ctx, right_body_id)?;

            assign_then_erase_next_stmt!(self, ctx, end_fork_id.upcast());

        }

        self.prev_stmt = end_fork_id.upcast();

        Ok(())

    }

    fn visit_select_stmt(&mut self, ctx: &mut Ctx, id: SelectStatementId) -> VisitorResult {

        let select_stmt = &ctx.heap[id];

        let end_select_id = select_stmt.end_select;

        // Select statements may only occur inside sync blocks

        if self.in_sync.is_invalid() {

            return Err(ParseError::new_error_str_at_span(

                &ctx.module().source, select_stmt.span,

                "select statements may only occur inside sync blocks"

            ));

        }

        if !self.def_type.is_primitive() {

            return Err(ParseError::new_error_str_at_span(

                &ctx.module().source, select_stmt.span,

                "select statements may only be used in primitive components"

            ));

        }

        // Visit the various arms in the select block

        let mut case_stmt_ids = self.statement_buffer.start_section();

        let num_cases = select_stmt.cases.len();

        for case in &select_stmt.cases {

            // Note: we add both to the buffer, retrieve them later in indexed

            // fashion

            case_stmt_ids.push(case.guard);

            case_stmt_ids.push(case.block.upcast());

        }

        assign_then_erase_next_stmt!(self, ctx, id.upcast());

        // Link up the "Select" with the "EndSelect". If there are no cases then

        // runtime should pick the "EndSelect" immediately.

        for idx in 0..num_cases {

            let base_idx = 2 * idx;

            let guard_id     = case_stmt_ids[base_idx    ];

            let arm_block_id = case_stmt_ids[base_idx + 1];

            // Visit the guard of this arm

            debug_assert!(self.in_select_guard.is_invalid());

            self.in_select_guard = id;

            self.in_select_arm = idx as u32;

            self.visit_stmt(ctx, guard_id)?;

            self.in_select_guard = SelectStatementId::new_invalid();

            // If the arm declares a variable, then add it to the variables of

            // this arm's code block

            match &ctx.heap[guard_id] {

                Statement::Local(LocalStatement::Memory(stmt)) => {

                    debug_assert_eq!(ctx.heap[arm_block_id].as_block().this.upcast(), arm_block_id); // backwards way of saying arm_block_id is a BlockStatementId

                    let block_stmt = BlockStatementId(arm_block_id);

                    let block_scope =  Scope::Regular(block_stmt);

                    self.checked_at_single_scope_add_local(ctx, block_scope, -1, stmt.variable)?;

                },

                Statement::Expression(_) => {},

                _ => unreachable!(), // just to be sure the parser produced the expected AST

            }

            // Visit the code associated with the guard

            self.visit_stmt(ctx, arm_block_id)?;

            assign_then_erase_next_stmt!(self, ctx, end_select_id.upcast());

        }

        self.in_select_guard = SelectStatementId::new_invalid();

        self.prev_stmt = end_select_id.upcast();

        Ok(())

    }

    fn visit_return_stmt(&mut self, ctx: &mut Ctx, id: ReturnStatementId) -> VisitorResult {

        // Check if "return" occurs within a function

        let stmt = &ctx.heap[id];

        if !self.def_type.is_function() {

            return Err(ParseError::new_error_str_at_span(

                &ctx.module().source, stmt.span,

                "return statements may only appear in function bodies"

            ));

        }

        // If here then we are within a function

        assign_then_erase_next_stmt!(self, ctx, id.upcast());

        debug_assert_eq!(self.expr_parent, ExpressionParent::None);

        debug_assert_eq!(ctx.heap[id].expressions.len(), 1);

        self.expr_parent = ExpressionParent::Return(id);

        self.visit_expr(ctx, ctx.heap[id].expressions[0])?;

        self.expr_parent = ExpressionParent::None;

        Ok(())

    }

    fn visit_goto_stmt(&mut self, ctx: &mut Ctx, id: GotoStatementId) -> VisitorResult {

        let target_id = self.find_label(ctx, &ctx.heap[id].label)?;

        ctx.heap[id].target = Some(target_id);

        let target = &ctx.heap[target_id];

        if self.in_sync != target.in_sync {

            // We can only goto the current scope or outer scopes. Because

            // nested sync statements are not allowed we must be inside a sync

            // statement.

            debug_assert!(!self.in_sync.is_invalid());

            let goto_stmt = &ctx.heap[id];

            let sync_stmt = &ctx.heap[self.in_sync];

            return Err(

                ParseError::new_error_str_at_span(&ctx.module().source, goto_stmt.span, "goto may not escape the surrounding synchronous block")

                .with_info_str_at_span(&ctx.module().source, target.label.span, "this is the target of the goto statement")

                .with_info_str_at_span(&ctx.module().source, sync_stmt.span, "which will jump past this statement")

            );

        }

        assign_then_erase_next_stmt!(self, ctx, id.upcast());

        Ok(())

    }

    fn visit_new_stmt(&mut self, ctx: &mut Ctx, id: NewStatementId) -> VisitorResult {

        // Make sure the new statement occurs inside a composite component

        if !self.def_type.is_composite() {

            let new_stmt = &ctx.heap[id];

            return Err(ParseError::new_error_str_at_span(

                &ctx.module().source, new_stmt.span,

                "instantiating components may only be done in composite components"

            ));

        }

        // Recurse into call expression (which will check the expression parent

        // to ensure that the "new" statment instantiates a component)

        let call_expr_id = ctx.heap[id].expression;

        assign_and_replace_next_stmt!(self, ctx, id.upcast());

        debug_assert_eq!(self.expr_parent, ExpressionParent::None);

        self.expr_parent = ExpressionParent::New(id);

        self.visit_call_expr(ctx, call_expr_id)?;

        self.expr_parent = ExpressionParent::None;

        Ok(())

    }

    fn visit_expr_stmt(&mut self, ctx: &mut Ctx, id: ExpressionStatementId) -> VisitorResult {

        let expr_id = ctx.heap[id].expression;

        assign_and_replace_next_stmt!(self, ctx, id.upcast());

        debug_assert_eq!(self.expr_parent, ExpressionParent::None);

        self.expr_parent = ExpressionParent::ExpressionStmt(id);

        self.visit_expr(ctx, expr_id)?;

        self.expr_parent = ExpressionParent::None;

        Ok(())

    }

    //--------------------------------------------------------------------------

    // Expression visitors

    //--------------------------------------------------------------------------

    fn visit_assignment_expr(&mut self, ctx: &mut Ctx, id: AssignmentExpressionId) -> VisitorResult {

        let upcast_id = id.upcast();

        let assignment_expr = &mut ctx.heap[id];

        // Although we call assignment an expression to simplify the compiler's

        // code (mainly typechecking), we disallow nested use in expressions

        match self.expr_parent {

            // Look at us: lying through our teeth while providing error messages.

            ExpressionParent::Memory(_) => {},

            ExpressionParent::ExpressionStmt(_) => {},

            _ => {

                let assignment_span = assignment_expr.full_span;

                return Err(ParseError::new_error_str_at_span(

                    &ctx.module().source, assignment_span,

                    "assignments are statements, and cannot be used in expressions"

                ))

            },

        }

        let left_expr_id = assignment_expr.left;

        let right_expr_id = assignment_expr.right;

        let old_expr_parent = self.expr_parent;

        assignment_expr.parent = old_expr_parent;

        assignment_expr.unique_id_in_definition = self.next_expr_index;

        self.next_expr_index += 1;

        self.expr_parent = ExpressionParent::Expression(upcast_id, 0);

        self.must_be_assignable = Some(assignment_expr.operator_span);

        self.visit_expr(ctx, left_expr_id)?;

        self.expr_parent = ExpressionParent::Expression(upcast_id, 1);

        self.must_be_assignable = None;

        self.visit_expr(ctx, right_expr_id)?;

        self.expr_parent = old_expr_parent;

        Ok(())

    }

    fn visit_binding_expr(&mut self, ctx: &mut Ctx, id: BindingExpressionId) -> VisitorResult {

        let upcast_id = id.upcast();

/**

 * protocol/tests.rs

 *

 * Contains tests for various parts of the lexer/parser and the evaluator of the

 * code. These are intended to be temporary tests such that we're sure that we

 * don't break existing functionality.

 *

 * In the future these should be replaced by proper testing protocols.

 *

 * If any of these tests fail, and you think they're not needed anymore, feel

 * free to cast them out into oblivion, where dead code goes to die.

 */

mod utils;

mod parser_binding;

mod parser_imports;

mod parser_inference;

mod parser_literals;

mod parser_monomorphs;

mod parser_validation;

mod eval_binding;

mod eval_calls;

mod eval_casting;

mod eval_operators;

mod eval_silly;

pub(crate) use utils::{Tester}; // the testing harness

pub(crate) use crate::protocol::eval::value::*; // to test functions

            return i;

        }"

    ).for_function("call", |f| { f

        .for_expression_by_source(

            "b0 + b1", "+", 

            |e| { e.assert_concrete_type("s8"); }

        )

        .for_expression_by_source(

            "s0 + s1", "+", 

            |e| { e.assert_concrete_type("s16"); }

        )

        .for_expression_by_source(

            "i0 + i1", "+", 

            |e| { e.assert_concrete_type("s32"); }

        )

        .for_expression_by_source(

            "l0 + l1", "+", 

            |e| { e.assert_concrete_type("s64"); }

        );

    });

    Tester::new_single_source_expect_err(

        "incompatible types", 

        "func call() -> s32 {

            s8 b = 0;

            s64 l = 1;

            auto r = b + l;

            return 0;

        }"

    ).error(|e| { e

        .assert_ctx_has(0, "b + l")

        .assert_msg_has(0, "cannot apply")

        .assert_occurs_at(0, "+")

        .assert_msg_has(1, "has type 's8'")

        .assert_msg_has(2, "has type 's64'");

    });

}

#[test]

fn test_tuple_inference() {

    Tester::new_single_source_expect_ok(

        "from tuple to variable",

        "

        func test() -> u32 {

            (u8,u16,u32,u64) tuple = (1, 2, 3, 4);

            auto a = tuple.0;

            auto b = tuple.1;

            auto c = tuple.2;

            auto d = tuple.3;

            return cast(a) + cast(b) + c + cast(d);

        }

        "

    ).for_function("test", |f| { f

        .for_variable("a", |v| { v.assert_concrete_type("u8"); })

        .for_variable("b", |v| { v.assert_concrete_type("u16"); })

        .for_variable("c", |v| { v.assert_concrete_type("u32"); })

        .for_variable("d", |v| { v.assert_concrete_type("u64"); })

        .call_ok(Some(Value::UInt32(10)));

    });

    Tester::new_single_source_expect_ok(

        "from variable to tuple",

        "

        func test() -> u32 {

            auto tuple = (1, 2, 3, 4);

            u8  a = tuple.0;

            u16 b = tuple.1;

            u32 c = tuple.2;

            u64 d = tuple.3;

            return cast(a) + cast(b) + c + cast(d);

        }

        "

    ).for_function("test", |f| { f

        .for_variable("tuple", |v| { v.assert_concrete_type("(u8,u16,u32,u64)"); })

        .call_ok(Some(Value::UInt32(10)));

    });

}

#[test]

fn test_struct_inference() {

    Tester::new_single_source_expect_ok(

        "by function calls",

        "

        struct Pair<T1, T2>{ T1 first, T2 second }

        func construct<T1, T2>(T1 first, T2 second) -> Pair<T1, T2> {

            return Pair{ first: first, second: second };

        }

        func fix_t1<T2>(Pair<s8, T2> arg) -> s32 { return 0; }

        func fix_t2<T1>(Pair<T1, s32> arg) -> s32 { return 0; }

        func test() -> s32 {

            auto first = 0;

            auto second = 1;

            auto pair = construct(first, second);

            fix_t1(pair);

            fix_t2(pair);

            return 0;

        }

        "

    ).for_function("test", |f| { f

        .for_variable("first", |v| { v

            .assert_parser_type("auto")

            .assert_concrete_type("s8");

        })

        .for_variable("second", |v| { v

            .assert_parser_type("auto")

            .assert_concrete_type("s32");

        })

        .for_variable("pair", |v| { v

            .assert_parser_type("auto")

            .assert_concrete_type("Pair<s8,s32>");

        });

    });

    Tester::new_single_source_expect_ok(

        "by field access",

        "

        struct Pair<T1, T2>{ T1 first, T2 second }

        func construct<T1, T2>(T1 first, T2 second) -> Pair<T1, T2> {

            return Pair{ first: first, second: second };

        }

        func test() -> s32 {

            auto first = 0;

            auto second = 1;

            auto pair = construct(first, second);

            s8 assign_first = 0;

            s64 assign_second = 1;

            pair.first = assign_first;

            pair.second = assign_second;

            return 0;

        }

        "

    ).for_function("test", |f| { f

        .for_variable("first", |v| { v

            .assert_parser_type("auto")

            .assert_concrete_type("s8");

        })

        .for_variable("second", |v| { v

            .assert_parser_type("auto")

            .assert_concrete_type("s64");

        })

        .for_variable("pair", |v| { v

            .assert_parser_type("auto")

            .assert_concrete_type("Pair<s8,s64>");

        });

    });

    Tester::new_single_source_expect_ok(

        "by nested field access",

        "

        struct Node<T1, T2>{ T1 l, T2 r }

        func construct<T1, T2>(T1 l, T2 r) -> Node<T1, T2> {

            return Node{ l: l, r: r };

        }

        func fix_poly<T>(Node<T, T> a) -> s32 { return 0; }

        func test() -> s32 {

            s8 assigned = 0;

            auto thing = construct(assigned, construct(0, 1));

            fix_poly(thing.r);

            thing.r.r = assigned;

            return 0;

        }

        ",

    ).for_function("test", |f| { f

        .for_variable("thing", |v| { v

            .assert_parser_type("auto")

            .assert_concrete_type("Node<s8,Node<s8,s8>>");

        });

    });

}

#[test]

fn test_enum_inference() {

    Tester::new_single_source_expect_ok(

        "no polymorphic vars",

        "

        enum Choice { A, B }

        func test_instances() -> s32 {

            auto foo = Choice::A;

            auto bar = Choice::B;

            return 0;

        }