/**

* Provides all statement classes.

*

* All statements have the common base class `Stmt`.

*/

import Element

import Location

import Member

import exprs.Expr

private import semmle.code.csharp.ExprOrStmtParent

private import semmle.code.csharp.frameworks.System

private import TypeRef

/**

* A statement.

*

* Either a block statement (`BlockStmt`), an expression statement (`ExprStmt`),

* a selection statement (`SelectionStmt`), a labeled statement (`LabeledStmt`),

* a loop statement (`LoopStmt`), a jump statement (`JumpStmt`), a `try` statement

* (`TryStmt`), a `catch` clause (`CatchClause`), a `checked` statement

* (`CheckedStmt`), an `unchecked` statement (`UncheckedStmt`), a `lock`

* statement (`LockStmt`), a `using` statement (`UsingStmt`), a local

* variable declaration statement (`LocalVariableDeclStmt`), an empty statement

* (`EmptyStmt`), an `unsafe` statement (`UnsafeStmt`), or a `fixed` statement

* (`FixedStmt`).

*/

class Stmt extends ControlFlowElement, @stmt {

/** Gets the enclosing callable of this statement. */

override Callable getEnclosingCallable() { enclosingCallable(this, result) }

override string toString() { result = "Statement" }

override Location getALocation() { stmt_location(this, result) }

/** Holds if this statement is a global statement. */

predicate isGlobal() { this.getParent().(BlockStmt).isGlobalStatementContainer() }

/**

* Gets the singleton statement contained in this statement, by removing

* enclosing block statements.

*

* For example converts `{ { return x; } }` to `return x;`.

*/

Stmt stripSingletonBlocks() { result = this }

/** Holds if this statement is compiler generated. */

predicate isCompilerGenerated() { compiler_generated(this) }

}

/**

* A block statement, for example

*

* ```csharp

* {

* ...

* }

* ```

*/

class BlockStmt extends Stmt, @block_stmt {

/** Gets a statement in this block, if any. */

Stmt getAStmt() { result.getParent() = this }

/** Gets the `n`th statement in this block. */

Stmt getStmt(int n) { result = this.getChild(n) }

/** Gets the number of statements in this block. */

int getNumberOfStmts() { result = count(this.getAStmt()) }

/** Gets the first statement in this block, if any. */

Stmt getFirstStmt() { result = this.getStmt(0) }

/** Gets the last statement in this block, if any. */

Stmt getLastStmt() { result = this.getStmt(this.getNumberOfStmts() - 1) }

/** Holds if this block is an empty block with no statements. */

predicate isEmpty() { not exists(this.getAStmt()) }

/** Holds if this block is the container of the global statements. */

predicate isGlobalStatementContainer() {

this.getEnclosingCallable().hasFullyQualifiedName("Program", "<Main>$")

}

override Stmt stripSingletonBlocks() {

if this.getNumberOfStmts() = 1

then result = this.getAChildStmt().stripSingletonBlocks()

else result = this

}

override string toString() { result = "{...}" }

override string getAPrimaryQlClass() { result = "BlockStmt" }

}

/**

* An expression statement, for example `M1()` on line 5

*

* ```csharp

* class C {

* int M1() { ... }

*

* void M2() {

* M1();

* }

* }

* ```

*/

class ExprStmt extends Stmt, @expr_stmt {

/** Gets the expression in this expression statement. */

Expr getExpr() { result.getParent() = this }

override string toString() { result = "...;" }

override string getAPrimaryQlClass() { result = "ExprStmt" }

}

/**

* A conditional statement.

*

* Either an `if` statement (`IfStmt`) or a `switch` statement (`SwitchStmt`).

*/

class SelectionStmt extends Stmt, @cond_stmt {

/** Gets the condition of this selection statement. */

Expr getCondition() { none() }

}

/**

* An `if` statement, for example

*

* ```csharp

* if (x==0) {

* ...

* } else {

* ...

* }

* ```

*

* The `else` part is optional.

*/

class IfStmt extends SelectionStmt, @if_stmt {

override Expr getCondition() { result = this.getChild(0) }

/** Gets the `then` (true) branch of this `if` statement. */

Stmt getThen() { result = this.getChild(1) }

/** Gets the `else` (false) branch of this `if` statement, if any. */

Stmt getElse() { result = this.getChild(2) }

override string toString() { result = "if (...) ..." }

override string getAPrimaryQlClass() { result = "IfStmt" }

}

/**

* A `switch` statement, for example

*

* ```csharp

* switch (instruction) {

* ...

* }

* ```

*/

class SwitchStmt extends SelectionStmt, Switch, @switch_stmt {

override Expr getExpr() { result = this.getChild(0) }

override Expr getCondition() { result = this.getExpr() }

/**

* Gets the `i`th `case` statement in the body of this `switch` statement.

*

* Example:

*

* ```csharp

* switch (x) {

* case "abc": // i = 0

* return 0;

* case int i when i > 0: // i = 1

* return 1;

* case string s: // i = 2

* Console.WriteLine(s);

* return 2;

* default: // i = 3

* return 3;

* }

* ```

* Note that this reorders the `default` case to always be at the end.

*/

override CaseStmt getCase(int i) { result = SwithStmtInternal::getCase(this, i) }

/** Gets a case of this `switch` statement. */

override CaseStmt getACase() { result = this.getCase(_) }

/** Gets a constant value case of this `switch` statement, if any. */

ConstCase getAConstCase() { result = this.getACase() }

/** Gets the default case of this `switch` statement, if any. */

DefaultCase getDefaultCase() { result = this.getACase() }

override string toString() { result = "switch (...) {...}" }

override string getAPrimaryQlClass() { result = "SwitchStmt" }

/**

* Gets the `i`th statement in the body of this `switch` statement.

*

* Example:

*

* ```csharp

* switch (x) {

* case "abc": // i = 0

* return 0;

* case int i when i > 0: // i = 1

* return 1;

* case string s: // i = 2

* Console.WriteLine(s);

* return 2; // i = 3

* default: // i = 4

* return 3; // i = 5

* }

* ```

*

* Note that each non-`default` case is a labeled statement, so the statement

* that follows is a child of the labeled statement, and not the `switch` block.

*/

Stmt getStmt(int i) { result = SwithStmtInternal::getStmt(this, i) }

/** Gets a statement in the body of this `switch` statement. */

Stmt getAStmt() { result = this.getStmt(_) }

}

cached

private module SwithStmtInternal {

cached

CaseStmt getCase(SwitchStmt ss, int i) {

exists(int index, int rankIndex |

caseIndex(ss, result, index) and

rankIndex = i + 1 and

index = rank[rankIndex](int j, CaseStmt cs | caseIndex(ss, cs, j) | j)

)

}

/** Implicitly reorder case statements to put the default case last if needed. */

private predicate caseIndex(SwitchStmt ss, CaseStmt case, int index) {

exists(int i | case = ss.getChildStmt(i) |

if case instanceof DefaultCase

then index = max(int j | exists(ss.getChildStmt(j))) + 1

else index = i

)

}

cached

Stmt getStmt(SwitchStmt ss, int i) {

exists(int index, int rankIndex |

result = ss.getChildStmt(index) and

rankIndex = i + 1 and

index =

rank[rankIndex](int j, Stmt s |

// `getChild` includes both labeled statements and the targeted

// statements of labeled statement as separate children, but we

// only want the labeled statement

s = getLabeledStmt(ss, j)

|

j

)

)

}

private Stmt getLabeledStmt(SwitchStmt ss, int i) {

result = ss.getChildStmt(i) and

not result = any(CaseStmt cs).getBody()

}

}

/** A `case` statement. */

class CaseStmt extends Case, @case_stmt {

override Expr getExpr() { result = any(SwitchStmt ss | ss.getACase() = this).getExpr() }

override PatternExpr getPattern() { result = this.getChild(0) }

override Stmt getBody() {

exists(int i, Stmt next |

this = this.getParent().getChild(i) and

next = this.getParent().getChild(i + 1)

|

result = next and

not result instanceof CaseStmt

or

result = next.(CaseStmt).getBody()

)

}

/**

* Gets the condition on this case, if any. For example, the type case on line 3

* has no condition, and the type case on line 4 has condition `s.Length > 0`, in

*

* ```csharp

* switch(p)

* {

* case int i:

* case string s when s.Length > 0:

* break;

* ...

* }

* ```

*/

override Expr getCondition() { result = this.getChild(1) }

/** Gets the `switch` statement that this `case` statement belongs to. */

SwitchStmt getSwitchStmt() { result.getACase() = this }

override string toString() { result = "case ...:" }

override string getAPrimaryQlClass() { result = "CaseStmt" }

}

/**

* A constant case of a `switch` statement, for example `case OpCode.Nop:`

* on line 2 in

*

* ```csharp

* switch (instruction) {

* case OpCode.Nop: ...

* default: ...

* }

* ```

*/

class ConstCase extends CaseStmt, LabeledStmt {

private ConstantPatternExpr p;

ConstCase() { p = this.getPattern() }

override string getLabel() { result = p.getValue() }

override string toString() { result = CaseStmt.super.toString() }

override string getAPrimaryQlClass() { result = "ConstCase" }

}

/**

* A default case of a `switch` statement, for example `default:` on

* line 3 in

*

* ```csharp

* switch (instruction) {

* case OpCode.Nop: ...

* default: ...

* }

* ```

*/

class DefaultCase extends CaseStmt, LabeledStmt {

DefaultCase() { not exists(Expr e | e.getParent() = this) }

override string getLabel() { result = "default" }

override string toString() { result = "default:" }

override string getAPrimaryQlClass() { result = "DefaultCase" }

}

/**

* A loop statement.

*

* Either a `while` statement (`WhileStmt`), a `do`-`while` statement

* (`DoStmt`), a `for` statement (`ForStmt`), or a `foreach` statement

* (`ForeachStmt`).

*/

class LoopStmt extends Stmt, @loop_stmt {

/** Gets the body of this loop statement. */

Stmt getBody() { result.getParent() = this }

/** Gets the condition of this loop statement, if any. */

Expr getCondition() { none() }

}

/**

* A `while` statement, for example

*

* ```csharp

* while (remaining > 0) {

* ...

* }

* ```

*/

class WhileStmt extends LoopStmt, @while_stmt {

override Expr getCondition() { result.getParent() = this }

override string toString() { result = "while (...) ..." }

override string getAPrimaryQlClass() { result = "WhileStmt" }

}

/**

* A `do`-`while` statement, for example

*

* ```csharp

* do {

* ...

* }

* while (remaining > 0);

* ```

*/

class DoStmt extends LoopStmt, @do_stmt {

override Expr getCondition() { result.getParent() = this }

override string toString() { result = "do ... while (...);" }

override string getAPrimaryQlClass() { result = "DoStmt" }

}

/**

* A `for` loop, for example

*

* ```csharp

* for (int i = 0; i < 10; i++) {

* ...

* }

* ```

*/

class ForStmt extends LoopStmt, @for_stmt {

/**

* Gets an initializer expression of this `for` loop, if any.

*

* For example, `i = 0` in

*

* ```csharp

* for (int i = 0; i < 10; i++) {

* ...

* }

* ```

*/

Expr getAnInitializer() { result = this.getInitializer(_) }

/**

* Gets the `n`th initializer expression of this `for` loop

* (starting at index 0).

*

* For example, the second (`n = 1`) initializer is `j = 10` in

*

* ```csharp

* for (int i = 0, j = 10; i < j; i++) {

* ...

* }

* ```

*/

Expr getInitializer(int n) {

exists(int i | result = this.getChild(i) and n = -1 - i and i <= -1)

}

override Expr getCondition() { result = this.getChild(0) }

/**

* Gets an update expression of this `for` loop, if any.

*

* For example, `i++` in

*

* ```csharp

* for (int i = 0; i < 10; i++) {

* ...

* }

* ```

*/

Expr getAnUpdate() { result = this.getUpdate(_) }

/**

* Gets the `n`th update expression of this `for` loop (starting at index 0).

*

* For example, the second (`n = 1`) update expression is `j--` in

*

* ```csharp

* for (int i = 0, j = 10; i < j; i++, j--) {

* ...

* }

* ```

*/

Expr getUpdate(int n) { exists(int i | result = this.getChild(i) and n = i - 1 and i >= 1) }

override string toString() { result = "for (...;...;...) ..." }

override string getAPrimaryQlClass() { result = "ForStmt" }

}

/**

* A `foreach` loop, for example

*

* ```csharp

* foreach (var item in items) {

* ...

* }

* ```

*/

class ForeachStmt extends LoopStmt, @foreach_stmt {

/**

* Gets the local variable of this `foreach` loop, if any.

*

* For example, `item` in

*

* ```csharp

* foreach (var item in items) {

* ...

* }

* ```

*/

LocalVariable getVariable() { result = this.getVariableDeclExpr().getVariable() }

/**

* Gets the local variable declaration of this `foreach` loop, if any.

*

* For example, `var item` in

*

* ```csharp

* foreach (var item in items) {

* ...

* }

* ```

*/

LocalVariableDeclExpr getVariableDeclExpr() { result = this.getChild(0) }

/**

* Gets the `i`th local variable declaration of this `foreach` loop.

*

* For example, `int a` is the 0th local variable declaration in

*

* ```csharp

* foreach ((int a, int b) in items) {

* ...

* }

* ```

*/

LocalVariableDeclExpr getVariableDeclExpr(int i) {

result = this.getVariableDeclTuple().getArgument(i)

or

i = 0 and result = this.getChild(0)

}

/**

* Gets the local variable declaration tuple of this `foreach` loop, if any.

* For example, `(int a, int b)` in

*

* ```csharp

* foreach ((int a, int b) in items) {

* ...

* }

* ```

*/

TupleExpr getVariableDeclTuple() { result = this.getChild(0) }

/**

* Gets the `i`th local variable of this `foreach` loop.

*

* For example, `a` is the 0th local variable in

*

* ```csharp

* foreach ((int a, int b) in items) {

* ...

* }

* ```

*/

LocalVariable getVariable(int i) { result = this.getVariableDeclExpr(i).getVariable() }

/**

* Gets a local variable of this `foreach` loop.

*

* For example, `a` and `b` in

*

* ```csharp

* foreach ((int a, int b) in items) {

* ...

* }

* ```

*/

LocalVariable getAVariable() { result = this.getVariable(_) }

/**

* Gets a local variable declaration of this `foreach` loop.

*

* For example, `int a` and `int b` in

*

* ```csharp

* foreach ((int a, int b) in items) {

* ...

* }

* ```

*/

LocalVariableDeclExpr getAVariableDeclExpr() { result = this.getVariableDeclExpr(_) }

override Expr getCondition() { none() }

/**

* Gets the expression that this `foreach` loop iterates over.

*

* For example, `items` in

*

* ```csharp

* foreach (var item in items) {

* ...

* }

* ```

*/

Expr getIterableExpr() { result = this.getChild(1) }

/** Gets the called `GetEnumerator` method. */

Method getGetEnumerator() { foreach_stmt_desugar(this, result, 1) }

/** Gets the called `MoveNext` or `MoveNextAsync` method. */

Method getMoveNext() { foreach_stmt_desugar(this, result, 3) }

/** Gets the called `Dispose` or `DisposeAsync` method, if any. */

Method getDispose() { foreach_stmt_desugar(this, result, 4) }

/** Gets the called `Current` property. */

Property getCurrent() { foreach_stmt_desugar(this, result, 2) }

/**

* Gets the intermediate type to which the `Current` property is converted before

* being converted to the iteration variable type.

*/

Type getElementType() { foreach_stmt_desugar(this, result, 5) }

/** Holds if this `foreach` statement is asynchronous. */

predicate isAsync() { foreach_stmt_info(this, 2) }

override string toString() { result = "foreach (... ... in ...) ..." }

override string getAPrimaryQlClass() { result = "ForeachStmt" }

}

/**

* A statement that changes the control flow and jumps to another statement.

*

* Either a `break` statement (`BreakStmt`), a `continue` statement (`ContinueStmt`),

* a `goto` statement (`GotoStmt`), a `throw` statement (`ThrowStmt`), a `return` statement

* (`ReturnStmt`), or a `yield` statement (`YieldStmt`).

*/

class JumpStmt extends Stmt, @jump_stmt { }

/**

* A `break` statement, for example line 4 in

*

* ```csharp

* while (true) {

* ...

* if (done)

* break;

* }

* ```

*/

class BreakStmt extends JumpStmt, @break_stmt {

override string toString() { result = "break;" }

override string getAPrimaryQlClass() { result = "BreakStmt" }

}

/**

* A `continue` statement, for example line 4 in

*

* ```csharp

* while (true) {

* ...

* if (!done)

* continue;

* ...

* }

* ```

*/

class ContinueStmt extends JumpStmt, @continue_stmt {

override string toString() { result = "continue;" }

override string getAPrimaryQlClass() { result = "ContinueStmt" }

}

/**

* A `goto` statement.

*

* Either a `goto` label (`GotoLabelStmt`), a `goto case` (`GotoCaseStmt`), or

* a `goto default` (`GotoDefaultStmt`).

*/

class GotoStmt extends JumpStmt, @goto_any_stmt {

/** Gets the label that this `goto` statement jumps to. */

string getLabel() { none() }

}

/**

* A `goto` statement that jumps to a labeled statement, for example line 4 in

*

* ```csharp

* while (true) {

* ...

* if (done)

* goto exit;

* }

* exit: ...

* ```

*/

class GotoLabelStmt extends GotoStmt, @goto_stmt {

override string getLabel() { exprorstmt_name(this, result) }

override string toString() { result = "goto ...;" }

/** Gets the target statement that this `goto` statement jumps to. */

LabeledStmt getTarget() {

result.getEnclosingCallable() = this.getEnclosingCallable() and

result.getLabel() = this.getLabel()

}

override string getAPrimaryQlClass() { result = "GotoLabelStmt" }

}

/**

* A `goto case` statement that jumps to a `switch` case.

*

* For example, line 5 in

*

* ```csharp

* switch (x) {

* case 0 :

* return 1;

* case 1 :

* goto case 0;

* default :

* return -1;

* }

* ```

*/

class GotoCaseStmt extends GotoStmt, @goto_case_stmt {

/** Gets the constant expression that this `goto case` statement jumps to. */

Expr getExpr() { result = this.getChild(0) }

override string getLabel() { result = this.getExpr().getValue() }

override string toString() { result = "goto case ...;" }

override string getAPrimaryQlClass() { result = "GotoCaseStmt" }

}

/**

* A `goto default` statement that jumps to the `default` case.

*

* For example, line 5 in

*

* ```csharp

* switch (x) {

* case 0 :

* return 1;

* case 1 :

* goto default;

* default :

* return -1;

* }

* ```

*/

class GotoDefaultStmt extends GotoStmt, @goto_default_stmt {

override string toString() { result = "goto default;" }

override string getLabel() { result = "default" }

override string getAPrimaryQlClass() { result = "GotoDefaultStmt" }

}

/**

* A `throw` statement, for example line 3 in

*

* ```csharp

* void M(string s) {

* if (s == null)

* throw new ArgumentNullException(nameof(s));

* }

* ```

*/

class ThrowStmt extends JumpStmt, ThrowElement, @throw_stmt {

override string toString() { result = "throw ...;" }

override ExceptionClass getThrownExceptionType() {

result = ThrowElement.super.getThrownExceptionType()

or

result = this.getRethrowParent().(CatchClause).getCaughtExceptionType()

}

private ControlFlowElement getRethrowParent() {

result = this and not exists(this.getExpr())

or

exists(ControlFlowElement mid |

mid = this.getRethrowParent() and

not mid instanceof CatchClause and

result = mid.getParent()

)

}

override string getAPrimaryQlClass() { result = "ThrowStmt" }

}

/**

* A class that derives from `System.Exception`,

* and may be thrown as an exception.

*/

class ExceptionClass extends Class {

ExceptionClass() { this.getBaseClass*() instanceof SystemExceptionClass }

}

/**

* A `return` statement, for example line 2 in

*

* ```csharp

* int M() {

* return 0;

* }

* ```

*/

class ReturnStmt extends JumpStmt, @return_stmt {

/** Gets the expression being returned, if any. */

Expr getExpr() { result.getParent() = this }

override string toString() { result = "return ...;" }

override string getAPrimaryQlClass() { result = "ReturnStmt" }

}

/**

* A `yield` statement.

*

* Either a `yield return` statement (`YieldReturnStmt`) or a

* `yield break` statement (`YieldBreakStmt`).

*/

class YieldStmt extends JumpStmt, @yield_stmt {

/** Gets the expression being yielded, if any. */

Expr getExpr() { result.getParent() = this }

}

/**

* A `yield break` statement, for example line 6 in

*

* ```csharp

* IEnumerable<int> DownFrom(int i) {

* while (true) {

* if (i > 0)

* yield return i--;

* else

* yield break;

* }

* }

* ```

*/

class YieldBreakStmt extends YieldStmt {

YieldBreakStmt() { not exists(this.getExpr()) }

override string toString() { result = "yield break;" }

override string getAPrimaryQlClass() { result = "YieldBreakStmt" }

}

/**

* A `yield return` statement, for example line 4 in

*

* ```csharp

* IEnumerable<int> DownFrom(int i) {

* while (true) {

* if (i > 0)

* yield return i--;

* else

* yield break;

* }

* }

* ```

*/

class YieldReturnStmt extends YieldStmt {

YieldReturnStmt() { exists(this.getExpr()) }

override string toString() { result = "yield return ...;" }

override string getAPrimaryQlClass() { result = "YieldReturnStmt" }

}

bindingset[cfe1, cfe2]

pragma[inline_late]

private predicate sameCallable(ControlFlowElement cfe1, ControlFlowElement cfe2) {

cfe1.getEnclosingCallable() = cfe2.getEnclosingCallable()

}

/**

* A `try` statement, for example

*

* ```csharp

* try {

* ...

* }

* catch (Exception e) {

* ...

* }

* finally {

* ...

* }

* ```

*/

class TryStmt extends Stmt, @try_stmt {

/** Gets the block of this `try` statement. */

BlockStmt getBlock() { result = this.getChild(0) }

/** Gets a `catch` clause of this `try` statement, if any. */

CatchClause getACatchClause() { result = this.getAChild() }

/** Gets the `n`th catch clause of this `try` statement. */

CatchClause getCatchClause(int n) { exists(int i | result = this.getChild(i) and n = i - 1) }

/** Gets the `finally` block of this `try` statement, if any. */

BlockStmt getFinally() { result = this.getChild(-1) }

/** Holds if this `try` statement has a `finally` block. */

predicate hasFinally() { exists(this.getFinally()) }

override string toString() { result = "try {...} ..." }

override string getAPrimaryQlClass() { result = "TryStmt" }

/** Gets the `catch` clause that handles an exception of type `ex`, if any. */

CatchClause getAnExceptionHandler(ExceptionClass ex) {

result = this.clauseHandlesException(ex, 0)

}

/**

* Holds if catch clause `cc` definitely handles exceptions of type `ex`.

*/

predicate definitelyHandles(ExceptionClass ex, CatchClause cc) {

cc = this.getACatchClause() and

not exists(cc.getFilterClause()) and

(

cc.getCaughtExceptionType() = ex.getBaseClass*()

or

cc instanceof GeneralCatchClause

)

}

private predicate maybeHandles(ExceptionClass ex, CatchClause cc) {

cc = this.getACatchClause() and

cc.getCaughtExceptionType().getBaseClass*() = ex

}

private CatchClause clauseHandlesException(ExceptionClass ex, int n) {

exists(CatchClause clause | clause = this.getCatchClause(n) |

if this.definitelyHandles(ex, clause)

then result = clause

else

if this.maybeHandles(ex, clause)

then

result = clause or

result = this.clauseHandlesException(ex, n + 1)

else

// Does not handle

result = this.clauseHandlesException(ex, n + 1)

)

}

/**

* Gets a control flow element that is tried by this `try` statement.

*

* That is, a child element that is not tried by another nested

* `try` statement.

*/

ControlFlowElement getATriedElement() {

result = this.getBlock()

or

exists(ControlFlowElement mid |

mid = this.getATriedElement() and

not mid instanceof TryStmt and

result = mid.getAChild() and

sameCallable(mid, result)

)

}

}

/**

* A `catch` clause within a `try` statement.

*

* Either a specific `catch` clause (`SpecificCatchClause`) or a

* general `catch` clause (`GeneralCatchClause`).

*/

class CatchClause extends Stmt, @catch {

/** Gets the `try` statement that this `catch` clause belongs to. */

TryStmt getTryStmt() { result.getACatchClause() = this }

/** Gets the block of this `catch` clause. */

BlockStmt getBlock() { result.getParent() = this }

/**

* Gets the type of the exception caught. For example, the type of the exception

* caught on line 4 is `System.IO.IOException` in

*

* ```csharp

* try {

* ...

* }

* catch (System.IO.IOException ex) {

* ...

* }

* ```

*/

ExceptionClass getCaughtExceptionType() {

catch_type(this, result, _)

or

not catch_type(this, any(Type t), _) and

catch_type(this, getTypeRef(result), _)

}