[GROOVY-8566] Array initialization from list literal without "as" should be supported under static compilation for multi-dimension arrays

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.4.15
• Fix Version/s: 5.0.0-alpha-11
• Component/s: Compiler, Static compilation, Static Type Checker
• Labels: CompileStatic array initialization

Language

groovy

• Assignee: Eric Milles
• Reporter: mgroovy
• Created: 01/May/18 14:13
• Updated: 12/Nov/24 11:39
• Resolved: 06/Oct/24 00:18

Description

Dynamic Groovy supports initializing an array from a list literal:

@Test
@Ignore
void arrayFromListLiteral() {
  int[] a0 = [1,2,3]
  int[][] aa0 = [[1,2,3],[4,5,6]]
  int[][][] aaa0 = [[[1],[2],[3]],[[4],[5],[6]]]
  int[][][] aaa1 = [[1,2,3],[4,5,6]]
  int[][][] aaa2 = [1,2,3,4,5,6]
  int[][][] aaa3 = 1

  println "a0=$a0"
  println "aa0=$aa0"
  println "aaa0=$aaa0"
  println "aaa1=$aaa1"
  println "aaa2=$aaa2"
  println "aaa3=$aaa3"

  assert a0 instanceof int[]
  assert aa0 instanceof int[][]
  assert aaa0 instanceof int[][][]
  assert aaa1 instanceof int[][][]
  assert aaa2 instanceof int[][][]
  assert aaa3 instanceof int[][][]
}

gives:

a0=[1, 2, 3]
aa0=[[1, 2, 3], [4, 5, 6]]
aaa0=[[[1], [2], [3]], [[4], [5], [6]]]
aaa1=[[[1], [2], [3]], [[4], [5], [6]]]
aaa2=[[[1]], [[2]], [[3]], [[4]], [[5]], [[6]]]
aaa3=[[[1]]]

Using @CompileStatic on the test the compiler gives:

Error:(37, 19) Groovyc: [Static type checking] - Cannot assign value of type java.util.List <java.lang.Integer> into array of type int[][]
Error:(38, 22) Groovyc: [Static type checking] - Cannot assign value of type java.util.List <java.util.List> into array of type int[][][]
Error:(39, 22) Groovyc: [Static type checking] - Cannot assign value of type java.util.List <java.lang.Integer> into array of type int[][][]
Error:(40, 22) Groovyc: [Static type checking] - Cannot assign value of type int into array of type int[][][]
Error:(41, 22) Groovyc: [Static type checking] - Cannot assign value of type int to variable of type int[][][]

Adding the "as" operator:

@Test
@Ignore
void arrayFromListLiteral() {
  int[] a0 = [1,2,3]
  int[][] aa0 = [[1,2,3],[4,5,6]] as int[][]
  int[][][] aaa0 = [[[1],[2],[3]],[[4],[5],[6]]]  as int[][][]
  // etc
}

makes the code work the same as in the dynamic case.

In light of the upcoming Groovy 3.0 support for Java-style curly-braces literal array syntax, it would be good to support the idiomatic Groovy array initialization syntax also for the static compilation case.

An additonal question would be, whether in the static case the automatic conversion of the RHS expression to fit the LHS array type should be less lenient, i.e. the list structure should be required to conform to the array dimensions given on the left ?

Issue Links

• relates to: GROOVY-11492 Java compatibility: array initializers without "new Type[]"