fix compiler crash due to certain redundant typecast expressions

compiler/src/prog8/compiler/Compiler.kt

@@ -253,7 +253,7 @@ private fun processAst(programAst: Program, errors: IErrorReporter, compilerOpti
     errors.report()
     programAst.addTypecasts(errors)
     errors.report()
-    programAst.variousCleanups(errors)
+    programAst.variousCleanups(programAst, errors)
     errors.report()
     programAst.checkValid(compilerOptions, errors, compilerOptions.compTarget)
     errors.report()
@@ -297,7 +297,7 @@ private fun optimizeAst(programAst: Program, errors: IErrorReporter, functions:
 private fun postprocessAst(programAst: Program, errors: IErrorReporter, compilerOptions: CompilationOptions) {
     programAst.addTypecasts(errors)
     errors.report()
-    programAst.variousCleanups(errors)
+    programAst.variousCleanups(programAst, errors)
     programAst.checkValid(compilerOptions, errors, compilerOptions.compTarget)          // check if final tree is still valid
     errors.report()
     val callGraph = CallGraph(programAst)

compiler/src/prog8/compiler/astprocessing/AstExtensions.kt

@@ -61,8 +61,8 @@ internal fun Program.checkIdentifiers(errors: IErrorReporter, compTarget: ICompi
     }
 }
 
-internal fun Program.variousCleanups(errors: IErrorReporter) {
+internal fun Program.variousCleanups(program: Program, errors: IErrorReporter) {
-    val process = VariousCleanups(errors)
+    val process = VariousCleanups(program, errors)
     process.visit(this)
     if(errors.noErrors())
         process.applyModifications()

compiler/src/prog8/compiler/astprocessing/VariousCleanups.kt

@@ -3,6 +3,7 @@ package prog8.compiler.astprocessing
 import prog8.ast.IFunctionCall
 import prog8.ast.INameScope
 import prog8.ast.Node
+import prog8.ast.Program
 import prog8.ast.base.FatalAstException
 import prog8.ast.base.Position
 import prog8.ast.expressions.*
@@ -12,7 +13,7 @@ import prog8.ast.walk.IAstModification
 import prog8.compiler.IErrorReporter
 
 
-internal class VariousCleanups(val errors: IErrorReporter): AstWalker() {
+internal class VariousCleanups(val program: Program, val errors: IErrorReporter): AstWalker() {
 
     override fun before(nopStatement: NopStatement, parent: Node): Iterable<IAstModification> {
         return listOf(IAstModification.Remove(nopStatement, parent as INameScope))
@@ -36,16 +37,6 @@ internal class VariousCleanups(val errors: IErrorReporter): AstWalker() {
         }
     }
 
-    override fun before(typecast: TypecastExpression, parent: Node): Iterable<IAstModification> {
-        if(typecast.expression is NumericLiteralValue) {
-            val value = (typecast.expression as NumericLiteralValue).cast(typecast.type)
-            if(value.isValid)
-                return listOf(IAstModification.ReplaceNode(typecast, value.valueOrZero(), parent))
-        }
-
-        return noModifications
-    }
-
     override fun before(functionCallStatement: FunctionCallStatement, parent: Node): Iterable<IAstModification> {
         return before(functionCallStatement as IFunctionCall, parent, functionCallStatement.position)
     }
@@ -69,6 +60,23 @@ internal class VariousCleanups(val errors: IErrorReporter): AstWalker() {
         return noModifications
     }
 
+    override fun after(typecast: TypecastExpression, parent: Node): Iterable<IAstModification> {
+        if(typecast.parent!==parent)
+            throw FatalAstException("parent node mismatch at $typecast")
+
+        if(typecast.expression is NumericLiteralValue) {
+            val value = (typecast.expression as NumericLiteralValue).cast(typecast.type)
+            if(value.isValid)
+                return listOf(IAstModification.ReplaceNode(typecast, value.valueOrZero(), parent))
+        }
+
+        val sourceDt = typecast.expression.inferType(program)
+        if(sourceDt.istype(typecast.type))
+            return listOf(IAstModification.ReplaceNode(typecast, typecast.expression, parent))
+
+        return noModifications
+    }
+
     override fun after(subroutine: Subroutine, parent: Node): Iterable<IAstModification> {
         if(subroutine.parent!==parent)
             throw FatalAstException("parent node mismatch at $subroutine")
@@ -99,12 +107,6 @@ internal class VariousCleanups(val errors: IErrorReporter): AstWalker() {
         return noModifications
     }
 
-    override fun after(typecast: TypecastExpression, parent: Node): Iterable<IAstModification> {
-        if(typecast.parent!==parent)
-            throw FatalAstException("parent node mismatch at $typecast")
-        return noModifications
-    }
-
     override fun after(returnStmt: Return, parent: Node): Iterable<IAstModification> {
         if(returnStmt.parent!==parent)
             throw FatalAstException("parent node mismatch at $returnStmt")

examples/test.p8

@@ -1,12 +1,11 @@
 
 main {
     sub start() {
+        uword width
 
-        uword world = $2000
+        ; TODO fix compiler crash with noopt:
-        ubyte xx
+        uword x1 = (width-1 as uword) + 2
 
-        ubyte chr = world[2]
-        ubyte chr2 = world[xx]
     }
 }