Package org.apache.groovy.contracts.ast

Class LoopInvariantASTTransformation

java.lang.Object
org.apache.groovy.contracts.ast.LoopInvariantASTTransformation
All Implemented Interfaces:
CompilationUnitAware, ASTTransformation
public class LoopInvariantASTTransformation extends Object implements ASTTransformation, CompilationUnitAware
Handles Invariant annotations placed on loop statements (for, while, do-while). For for and while loops the invariant closure is evaluated as an assertion at the start of each loop iteration. For do-while loops it is evaluated after each body execution instead (GROOVY-12128): the body runs before the first condition check, so the invariant only needs to be established by that first execution — checking it at loop entry would reject valid loops. (A continue inside a do-while jumps straight to the condition and therefore skips the check for that pass.)

When @Invariant is placed on a class (its original usage), this transform returns immediately, letting the existing global contract pipeline handle it.

Example: 

 int sum = 0
 @Invariant({ 0 <= i && i <= 4 })
 for (int i in 0..4) {
     sum += i
 }
Since:
6.0.0
See Also:

  • Constructor Details

    • LoopInvariantASTTransformation

      public LoopInvariantASTTransformation()

  • Method Details

    • setCompilationUnit

      public void setCompilationUnit(CompilationUnit unit)
      Description copied from interface: CompilationUnitAware
      Sets the compilation unit currently applying this transformation.
      Specified by:
      setCompilationUnit in interface CompilationUnitAware
      Parameters:
      unit - the active compilation unit

    • visit

      public void visit(ASTNode[] nodes, SourceUnit source)
      Rewrites a loop-level Invariant annotation into assertion checks injected at the start of the loop body.
      Specified by:
      visit in interface ASTTransformation
      Parameters:
      nodes - the annotated AST nodes supplied by the compiler
      source - the current source unit