allow boolean when conditions, optimize into a regular if

codeOptimizers/src/prog8/optimizer/StatementOptimizer.kt

@@ -391,4 +391,47 @@ class StatementOptimizer(private val program: Program,
         else
             noModifications
     }
+
+    override fun after(whenStmt: When, parent: Node): Iterable<IAstModification> {
+
+        fun replaceWithIf(condition: Expression, trueBlock: AnonymousScope, elseBlock: AnonymousScope?): List<IAstModification> {
+            val ifStmt = IfElse(condition, trueBlock, elseBlock ?: AnonymousScope(mutableListOf(), whenStmt.position), whenStmt.position)
+            errors.warn("for boolean condition a normal if statement is preferred", whenStmt.position)
+            return listOf(IAstModification.ReplaceNode(whenStmt, ifStmt, parent))
+        }
+
+        if(whenStmt.condition.inferType(program).isBool) {
+            if(whenStmt.choices.all { it.values?.size==1 }) {
+                if (whenStmt.choices.all { it.values!!.single().constValue(program)!!.number in arrayOf(0.0, 1.0) }) {
+                    // it's a when statement on booleans that can just be replaced by an if or if..else.
+                    if (whenStmt.choices.size == 1) {
+                        return if(whenStmt.choices[0].values!![0].constValue(program)!!.number==1.0) {
+                            replaceWithIf(whenStmt.condition, whenStmt.choices[0].statements, null)
+                        } else {
+                            val notCondition = BinaryExpression(whenStmt.condition, "==", NumericLiteral(DataType.UBYTE, 0.0, whenStmt.condition.position), whenStmt.condition.position)
+                            replaceWithIf(notCondition, whenStmt.choices[0].statements, null)
+                        }
+                    } else if (whenStmt.choices.size == 2) {
+                        var trueBlock: AnonymousScope? = null
+                        var elseBlock: AnonymousScope? = null
+                        if(whenStmt.choices[0].values!![0].constValue(program)!!.number==1.0) {
+                            trueBlock = whenStmt.choices[0].statements
+                        } else {
+                            elseBlock = whenStmt.choices[0].statements
+                        }
+                        if(whenStmt.choices[1].values!![0].constValue(program)!!.number==1.0) {
+                            trueBlock = whenStmt.choices[1].statements
+                        } else {
+                            elseBlock = whenStmt.choices[1].statements
+                        }
+                        if(trueBlock!=null && elseBlock!=null) {
+                            return replaceWithIf(whenStmt.condition, trueBlock, elseBlock)
+                        }
+                    }
+                }
+            }
+        }
+        return noModifications
+    }
+
 }

compiler/src/prog8/compiler/astprocessing/AstChecker.kt

@@ -1341,8 +1341,14 @@ internal class AstChecker(private val program: Program,
                     constvalue == null -> errors.err("choice value must be a constant", whenChoice.position)
                     constvalue.type !in IntegerDatatypes -> errors.err("choice value must be a byte or word", whenChoice.position)
                     conditionType isnot constvalue.type -> {
-                        if(conditionType.isKnown)
+                        if(conditionType.isKnown) {
-                            errors.err("choice value datatype differs from condition value", whenChoice.position)
+                            if(conditionType.istype(DataType.BOOL)) {
+                                if(constvalue.number!=0.0 && constvalue.number!=1.0)
+                                    errors.err("choice value datatype differs from condition value", whenChoice.position)
+                            } else {
+                                errors.err("choice value datatype differs from condition value", whenChoice.position)
+                            }
+                        }
                     }
                 }
             }

compiler/test/ast/TestVariousCompilerAst.kt

@@ -334,5 +334,22 @@ main {
 }"""
         compileText(VMTarget(), optimize=false, src, writeAssembly=false) shouldNotBe null
     }
+
+    test("when on booleans") {
+        val src = """
+main
+{
+    sub start()
+    {
+        bool choiceVariable=true
+        when choiceVariable {
+          false -> cx16.r0++
+          true -> cx16.r1++
+        }
+    }
+}"""
+
+        compileText(VMTarget(), optimize=false, src, writeAssembly=false) shouldNotBe null
+    }
 })
 

examples/test.p8

@@ -1,32 +1,16 @@
 %import textio
 %zeropage basicsafe
 
-; (127 instructions in 15 chunks, 47 registers)
+main
-; 679 steps
+{
-
+    ; 00f9
-
+    sub start()
-main {
+    {
-
+        bool rasterIrqAfterSubs=false
-sub start() {
+        when rasterIrqAfterSubs {
-    uword i
+          false -> txt.print("false\n")
-    uword n
+          true -> txt.print("true\n")
-
+        }
-    repeat 10 {
+        txt.print("done")
-        txt.chrout('.')
-    }
-    txt.nl()
-    
-    n=10
-    for i in 0 to n step 3 {
-        txt.print_uw(i)
-        txt.nl()
-    }
-    txt.nl()
-
-    n=0
-    for i in 10 downto n step -3 {
-        txt.print_uw(i)
-        txt.nl()
     }
 }
-}

gradle.properties

@@ -5,4 +5,4 @@ org.gradle.daemon=true
 kotlin.code.style=official
 javaVersion=11
 kotlinVersion=1.9.0
-version=9.1
+version=9.2-SNAPSHOT