Document safety of generated Java casts in java-transient-0

1 files changed, 12 insertions, 0 deletions

diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/javatransient0/JavaTransient0Generator.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/javatransient0/JavaTransient0Generator.java
index 78cbca4..1999cc8 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/javatransient0/JavaTransient0Generator.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/javatransient0/JavaTransient0Generator.java
@@ -225,6 +225,8 @@ public class JavaTransient0Generator implements Generator {
 
     private JavaMethodDeclaration generateDecodeInt8Method() {
         var statements = List.<JavaBlockStatement>of(
+            // InputStream.read() returns a byte of data as an int, so casting
+            // to a byte is safe.
             new JavaReturn(new JavaCast(
                 JavaTypeRef.BYTE,
                 generateInputStreamRead()
@@ -267,6 +269,8 @@ public class JavaTransient0Generator implements Generator {
                 );
 
                 if (bits > 32) {
+                    // byteToWrite should only represent a byte of data, so
+                    // casting to int is safe.
                     byteToWrite = new JavaCast(JavaTypeRef.INT, byteToWrite);
                 }
 
@@ -334,6 +338,7 @@ public class JavaTransient0Generator implements Generator {
         ));
 
         statements.addAll(generateEncode(
+            // The length of a string is an int, so casting to long is safe.
             new JavaCast(JavaTypeRef.LONG, new JavaFieldAccess(
                 new JavaRef(bytesVariableName),
                 JavaIdentifier.of("length")
@@ -383,6 +388,10 @@ public class JavaTransient0Generator implements Generator {
             Optional.of(new JavaMethodCall(
                 new JavaRef(INPUT_STREAM_NAME),
                 JavaIdentifier.of("readNBytes"),
+                // We've checked above that the length is less than
+                // Integer.MAX_VALUE, so casting to an int is safe.
+                // (This doesn't check for negatives, but readNBytes() fails for
+                // negative values anyway.)
                 List.of(new JavaCast(JavaTypeRef.INT, new JavaRef(bytesLengthVariableName)))
             ))
         ));
@@ -872,6 +881,7 @@ public class JavaTransient0Generator implements Generator {
         var statements = new ArrayList<JavaBlockStatement>();
 
         statements.addAll(generateEncode(
+            // The size of the list is an int, so casting to a long is safe.
             new JavaCast(JavaTypeRef.LONG, new JavaMethodCall(
                 value,
                 JavaIdentifier.of("size"),
@@ -1069,6 +1079,8 @@ public class JavaTransient0Generator implements Generator {
                                 JavaIdentifier.of("put"),
                                 List.of(
                                     this.taggedSharedValue(value, type),
+                                    // The size of the shared values map is an
+                                    // int, so casting to a long is safe.
                                     new JavaCast(JavaTypeRef.LONG, new JavaMethodCall(
                                         new JavaRef(SHARED_VALUES_NAME),
                                         JavaIdentifier.of("size"),