Evolving past reference type patterns

[Brian Goetz]

>   * asking if something fits in the range of a byte or int; doing this
>     by hand is annoying and error-prone
>   * asking if casting from long to int would produce truncation; doing
>     this by hand is annoying and error-prone
>
>
Here’s some real code I wrote recently that would benefit dramatically 
from this:

|default CodeBuilder constantInstruction(int value) { return with(switch 
(value) { case -1 -> ConstantInstruction.ofIntrinsic(Opcode.ICONST_M1); 
case 0 -> ConstantInstruction.ofIntrinsic(Opcode.ICONST_0); case 1 -> 
ConstantInstruction.ofIntrinsic(Opcode.ICONST_1); case 2 -> 
ConstantInstruction.ofIntrinsic(Opcode.ICONST_2); case 3 -> 
ConstantInstruction.ofIntrinsic(Opcode.ICONST_3); case 4 -> 
ConstantInstruction.ofIntrinsic(Opcode.ICONST_4); case 5 -> 
ConstantInstruction.ofIntrinsic(Opcode.ICONST_5); default -> { if (value 
 >= -128 && value <= 127) { yield 
ConstantInstruction.ofArgument(Opcode.BIPUSH, value); } else if (value 
 >= -32768 && value <= 32767) { yield 
ConstantInstruction.ofArgument(Opcode.SIPUSH, value); } else { yield 
ConstantInstruction.ofLoad(Opcode.LDC, 
BytecodeHelpers.constantEntry(constantPool(), value)); } } }); } |

could become the less error-prone and uniform:

|default CodeBuilder constantInstruction(int value) { return with(switch 
(value) { case -1 -> ConstantInstruction.ofIntrinsic(Opcode.ICONST_M1); 
case 0 -> ConstantInstruction.ofIntrinsic(Opcode.ICONST_0); case 1 -> 
ConstantInstruction.ofIntrinsic(Opcode.ICONST_1); case 2 -> 
ConstantInstruction.ofIntrinsic(Opcode.ICONST_2); case 3 -> 
ConstantInstruction.ofIntrinsic(Opcode.ICONST_3); case 4 -> 
ConstantInstruction.ofIntrinsic(Opcode.ICONST_4); case 5 -> 
ConstantInstruction.ofIntrinsic(Opcode.ICONST_5); case byte value -> 
ConstantInstruction.ofArgument(Opcode.BIPUSH, value); case short value 
-> ConstantInstruction.ofArgument(Opcode.SIPUSH, value); default -> 
ConstantInstruction.ofLoad(Opcode.LDC, 
BytecodeHelpers.constantEntry(constantPool(), value)); }); } |

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