allow assignments between different pointer types

casts between pointer types will generate a llvm bitcast statement

e.g.
x : INT; p : POINTER TO BYTE;
p := &x;

fixes #463

Author: riederm

src/codegen/llvm_typesystem.rs

@@ -111,6 +111,18 @@ fn create_llvm_extend_int_value<'a>(
     }
 }
 
+///
+/// generates a cast from the given `value` to the given `target_type` if necessary and returns the casted value. It returns
+/// the original `value` if no cast is necessary
+///
+/// - `llvm` the llvm utilities to use for code-generation
+/// - `index` the current Index used for type-lookups
+/// - `llvm_type_index` the type index to lookup llvm generated types
+/// - `target_type` the expected target type of the value
+/// - `value` the value to (maybe) cast
+/// - `value_type` the current type of the given value
+/// - `statement` the original statement as a context (e.g. for error reporting)
+///
 pub fn cast_if_needed<'ctx>(
     llvm: &Llvm<'ctx>,
     index: &Index,
@@ -303,8 +315,15 @@ pub fn cast_if_needed<'ctx>(
                 )
                 .into()),
             DataTypeInformation::Pointer { .. } | DataTypeInformation::Void { .. } => {
-                //this is ok, no cast required
-                Ok(value)
+                let target_ptr_type =
+                    llvm_type_index.get_associated_type(target_type.get_name())?;
+                if value.get_type() != target_ptr_type {
+                    // bit-cast necessary
+                    Ok(builder.build_bitcast(value, target_ptr_type, ""))
+                } else {
+                    //this is ok, no cast required
+                    Ok(value)
+                }
             }
             _ => Err(Diagnostic::casting_error(
                 value_type.get_name(),

src/codegen/tests/expression_tests.rs

@@ -290,7 +290,7 @@ fn cast_lword_to_pointer() {
         FUNCTION baz : INT
             VAR 
                 ptr_x : POINTER TO INT; 
-                y : LWORD; 
+                y : LWORD;
             END_VAR;
 
             ptr_x := y;
@@ -302,6 +302,73 @@ fn cast_lword_to_pointer() {
     insta::assert_snapshot!(result);
 }
 
+#[test]
+fn cast_between_pointer_types() {
+    let result = codegen(
+        r#"
+        PROGRAM baz
+            VAR 
+                ptr_x : POINTER TO BYTE; 
+                y : WORD;
+            END_VAR;
+
+            ptr_x := &y;
+        END_PROGRAM
+    "#,
+    );
+
+    //should result in bitcast conversion when assigning to ptr_x
+    insta::assert_snapshot!(result);
+}
+
+#[test]
+fn unnecessary_casts_between_pointer_types() {
+    let result = codegen(
+        r#"
+        TYPE MyByte : BYTE; END_TYPE
+        
+        PROGRAM baz
+            VAR 
+                ptr : POINTER TO BYTE; 
+                b : BYTE;
+                si : SINT;
+                mb : MyByte;
+            END_VAR;
+
+            ptr := &b; //no cast necessary
+            ptr := &si; //no cast necessary
+            ptr := &mb; //no cast necessary
+        END_PROGRAM
+    "#,
+    );
+
+    //should not result in bitcast
+    insta::assert_snapshot!(result);
+}
+
+#[test]
+fn access_string_via_byte_array() {
+    let result = codegen(
+        r#"
+        TYPE MyByte : BYTE; END_TYPE
+        
+        PROGRAM baz
+            VAR 
+                str: STRING[10];
+                ptr : POINTER TO BYTE; 
+                bytes : POINTER TO ARRAY[0..9] OF BYTE;
+            END_VAR;
+
+            ptr := &str; //bit-cast expected
+            bytes := &str;
+        END_PROGRAM
+    "#,
+    );
+
+    //should result in bitcasts
+    insta::assert_snapshot!(result);
+}
+
 #[test]
 fn pointer_arithmetics() {
     // codegen should be successful for binary expression for pointer<->int / int<->pointer / pointer<->pointer

src/codegen/tests/snapshots/rusty__codegen__tests__code_gen_tests__pointers_generated.snap

@@ -1,6 +1,6 @@
 ---
 source: src/codegen/tests/code_gen_tests.rs
-assertion_line: 1718
+assertion_line: 1719
 expression: result
 
 ---
@@ -16,8 +16,8 @@ entry:
   %X = getelementptr inbounds %prg_interface, %prg_interface* %0, i32 0, i32 0
   %pX = getelementptr inbounds %prg_interface, %prg_interface* %0, i32 0, i32 1
   %rX = getelementptr inbounds %prg_interface, %prg_interface* %0, i32 0, i32 2
-  store i32* null, i8** %pX, align 8
-  store i32* null, i8** %rX, align 8
+  store i8* null, i8** %pX, align 8
+  store i8* null, i8** %rX, align 8
   store i8* %X, i8** %pX, align 8
   store i8* %X, i8** %rX, align 8
   %deref = load i8*, i8** %pX, align 8

src/codegen/tests/snapshots/rusty__codegen__tests__expression_tests__access_string_via_byte_array.snap

@@ -0,0 +1,25 @@
+---
+source: src/codegen/tests/expression_tests.rs
+assertion_line: 370
+expression: result
+
+---
+; ModuleID = 'main'
+source_filename = "main"
+
+%baz_interface = type { [11 x i8], i8*, [10 x i8]* }
+
+@baz_instance = global %baz_interface zeroinitializer
+
+define void @baz(%baz_interface* %0) {
+entry:
+  %str = getelementptr inbounds %baz_interface, %baz_interface* %0, i32 0, i32 0
+  %ptr = getelementptr inbounds %baz_interface, %baz_interface* %0, i32 0, i32 1
+  %bytes = getelementptr inbounds %baz_interface, %baz_interface* %0, i32 0, i32 2
+  %1 = bitcast [11 x i8]* %str to i8*
+  store i8* %1, i8** %ptr, align 8
+  %2 = bitcast [11 x i8]* %str to [10 x i8]*
+  store [10 x i8]* %2, [10 x i8]** %bytes, align 8
+  ret void
+}
+

src/codegen/tests/snapshots/rusty__codegen__tests__expression_tests__cast_between_pointer_types.snap

@@ -0,0 +1,22 @@
+---
+source: src/codegen/tests/expression_tests.rs
+assertion_line: 321
+expression: result
+
+---
+; ModuleID = 'main'
+source_filename = "main"
+
+%baz_interface = type { i8*, i16 }
+
+@baz_instance = global %baz_interface zeroinitializer
+
+define void @baz(%baz_interface* %0) {
+entry:
+  %ptr_x = getelementptr inbounds %baz_interface, %baz_interface* %0, i32 0, i32 0
+  %y = getelementptr inbounds %baz_interface, %baz_interface* %0, i32 0, i32 1
+  %1 = bitcast i16* %y to i8*
+  store i8* %1, i8** %ptr_x, align 8
+  ret void
+}
+

src/codegen/tests/snapshots/rusty__codegen__tests__expression_tests__unnecessary_casts_between_pointer_types.snap

@@ -0,0 +1,25 @@
+---
+source: src/codegen/tests/expression_tests.rs
+assertion_line: 346
+expression: result
+
+---
+; ModuleID = 'main'
+source_filename = "main"
+
+%baz_interface = type { i8*, i8, i8, i8 }
+
+@baz_instance = global %baz_interface zeroinitializer
+
+define void @baz(%baz_interface* %0) {
+entry:
+  %ptr = getelementptr inbounds %baz_interface, %baz_interface* %0, i32 0, i32 0
+  %b = getelementptr inbounds %baz_interface, %baz_interface* %0, i32 0, i32 1
+  %si = getelementptr inbounds %baz_interface, %baz_interface* %0, i32 0, i32 2
+  %mb = getelementptr inbounds %baz_interface, %baz_interface* %0, i32 0, i32 3
+  store i8* %b, i8** %ptr, align 8
+  store i8* %si, i8** %ptr, align 8
+  store i8* %mb, i8** %ptr, align 8
+  ret void
+}
+

src/resolver/tests/resolve_expressions_tests.rs

@@ -698,6 +698,7 @@ fn pointer_expressions_resolve_types() {
 
     assert_eq!(format!("{:?}", expected_types), format!("{:?}", type_names));
 }
+
 #[test]
 fn array_expressions_resolve_types() {
     let (unit, index) = index(
@@ -2921,6 +2922,33 @@ fn adress_of_is_annotated_correctly() {
     }
 }
 
+#[test]
+fn pointer_assignment_with_incompatible_types_hints_correctly() {
+    let (unit, mut index) = index(
+        "PROGRAM PRG
+                VAR
+                    x : INT;
+                    pt : POINTER TO BYTE;
+                END_VAR
+                pt := &x;
+            END_PROGRAM",
+    );
+
+    let annotations = annotate(&unit, &mut index);
+    let assignment = &unit.implementations[0].statements[0];
+
+    if let AstStatement::Assignment { left, right, .. } = assignment {
+        assert_type_and_hint!(&annotations, &index, left, "__PRG_pt", None);
+        assert_type_and_hint!(
+            &annotations,
+            &index,
+            right,
+            "POINTER_TO_INT",
+            Some("__PRG_pt")
+        );
+    }
+}
+
 #[test]
 fn call_on_function_block_array() {
     //GIVEN