fix: Fix invalid codegen on small to long int cast (#1921)

Author: dcodeIO

Diff for: src/compiler.ts

@@ -3521,10 +3521,10 @@ export class Compiler extends DiagnosticEmitter {
     if (currentType != contextualType.nonNullableType) { // allow assigning non-nullable to nullable
       if (constraints & Constraints.CONV_EXPLICIT) {
         expr = this.convertExpression(expr, currentType, contextualType, true, expression);
-        this.currentType = contextualType;
+        this.currentType = currentType = contextualType;
       } else if (constraints & Constraints.CONV_IMPLICIT) {
         expr = this.convertExpression(expr, currentType, contextualType, false, expression);
-        this.currentType = contextualType;
+        this.currentType = currentType = contextualType;
       }
     }
     if (wrap) expr = this.ensureSmallIntegerWrap(expr, currentType);

Diff for: src/flow.ts

@@ -1351,6 +1351,13 @@ export class Flow {
           case UnaryOp.ClzI32:
           case UnaryOp.CtzI32:
           case UnaryOp.PopcntI32: return type.size < 7;
+
+          // sign extensions overflow if result can have high garbage bits in the target type
+          case UnaryOp.Extend8I32: return type.size < (type.isUnsignedIntegerValue ? 32 : 8);
+          case UnaryOp.Extend8I64: return type.size < (type.isUnsignedIntegerValue ? 64 : 8);
+          case UnaryOp.Extend16I32: return type.size < (type.isUnsignedIntegerValue ? 32 : 16);
+          case UnaryOp.Extend16I64: return type.size < (type.isUnsignedIntegerValue ? 64 : 16);
+          case UnaryOp.Extend32I64: return type.size < (type.isUnsignedIntegerValue ? 64 : 32);
         }
         break;
       }

Diff for: tests/compiler/abi.untouched.wat

@@ -88,7 +88,6 @@
    local.set $0
   end
   local.get $0
-  i32.extend8_s
   i32.eqz
   i32.eqz
   if
@@ -176,7 +175,6 @@
  )
  (func $abi/exportedExported (result i32)
   call $abi/exported
-  i32.extend8_s
  )
  (func $abi/exportedInternal (result i32)
   call $abi/internal

Diff for: tests/compiler/cast.json

@@ -0,0 +1,4 @@
+{
+  "asc_flags": [
+  ]
+}

Diff for: tests/compiler/cast.optimized.wat

@@ -0,0 +1,4 @@
+(module
+ (memory $0 0)
+ (export "memory" (memory $0))
+)

Diff for: tests/compiler/cast.ts

@@ -0,0 +1,96 @@
+function test<T,U>(x: T): U {
+  // @ts-ignore
+  var y = x as U;
+  // @ts-ignore
+  return y;
+}
+
+test<i8,i8>(0);
+test<i8,u8>(0);
+test<i8,i16>(0);
+test<i8,u16>(0);
+test<i8,i32>(0);
+test<i8,u32>(0);
+test<i8,i64>(0);
+test<i8,u64>(0);
+test<i8,bool>(0);
+
+test<u8,i8>(0);
+test<u8,u8>(0);
+test<u8,i16>(0);
+test<u8,u16>(0);
+test<u8,i32>(0);
+test<u8,u32>(0);
+test<u8,i64>(0);
+test<u8,u64>(0);
+test<u8,bool>(0);
+
+test<i16,i8>(0);
+test<i16,u8>(0);
+test<i16,i16>(0);
+test<i16,u16>(0);
+test<i16,i32>(0);
+test<i16,u32>(0);
+test<i16,i64>(0);
+test<i16,u64>(0);
+test<i16,bool>(0);
+
+test<u16,i8>(0);
+test<u16,u8>(0);
+test<u16,i16>(0);
+test<u16,u16>(0);
+test<u16,i32>(0);
+test<u16,u32>(0);
+test<u16,i64>(0);
+test<u16,u64>(0);
+test<u16,bool>(0);
+
+test<i32,i8>(0);
+test<i32,u8>(0);
+test<i32,i16>(0);
+test<i32,u16>(0);
+test<i32,i32>(0);
+test<i32,u32>(0);
+test<i32,i64>(0);
+test<i32,u64>(0);
+test<i32,bool>(0);
+
+test<u32,i8>(0);
+test<u32,u8>(0);
+test<u32,i16>(0);
+test<u32,u16>(0);
+test<u32,i32>(0);
+test<u32,u32>(0);
+test<u32,i64>(0);
+test<u32,u64>(0);
+test<u32,bool>(0);
+
+test<i64,i8>(0);
+test<i64,u8>(0);
+test<i64,i16>(0);
+test<i64,u16>(0);
+test<i64,i32>(0);
+test<i64,u32>(0);
+test<i64,i64>(0);
+test<i64,u64>(0);
+test<i64,bool>(0);
+
+test<u64,i8>(0);
+test<u64,u8>(0);
+test<u64,i16>(0);
+test<u64,u16>(0);
+test<u64,i32>(0);
+test<u64,u32>(0);
+test<u64,i64>(0);
+test<u64,u64>(0);
+test<u64,bool>(0);
+
+test<bool,i8>(0);
+test<bool,u8>(0);
+test<bool,i16>(0);
+test<bool,u16>(0);
+test<bool,i32>(0);
+test<bool,u32>(0);
+test<bool,i64>(0);
+test<bool,u64>(0);
+test<bool,bool>(0);