feat: builtins ADR and REF now have a CONSTANT return specifier so th…

…ey can be used in initializers Allows parsing of the `CONSTANT` keyword when parsing POUs, however for now only the builtins are actually allowed to make use of this keyword. This enables the const-evaluator to check for constant builtins when trying to evaluate call-statements in variable initializers.
PLC-lang · Oct 3, 2024 · cb99b76 · cb99b76
1 parent bb5fe4b
commit cb99b76
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Showing 16 changed files with 320 additions and 34 deletions.
diff --git a/compiler/plc_ast/src/ast.rs b/compiler/plc_ast/src/ast.rs
@@ -42,6 +42,7 @@ pub struct Pou {
     pub generics: Vec<GenericBinding>,
     pub linkage: LinkageType,
     pub super_class: Option<String>,
+    pub is_const: bool,
 }
 
 #[derive(Debug, PartialEq, Eq)]

diff --git a/compiler/plc_diagnostics/src/diagnostics/diagnostics_registry.rs b/compiler/plc_diagnostics/src/diagnostics/diagnostics_registry.rs
@@ -206,6 +206,7 @@ lazy_static! {
         E102,   Error,      include_str!("./error_codes/E102.md"),  // Template variable without hardware binding
         E103,   Error,      include_str!("./error_codes/E103.md"),  // Immutable Hardware Binding
         E104,   Error,      include_str!("./error_codes/E104.md"),  // Config Variable With Incomplete Address
+        E105,   Error,      include_str!("./error_codes/E105.md"),  // CONSTANT keyword in POU
     );
 }
 

diff --git a/compiler/plc_diagnostics/src/diagnostics/error_codes/E105.md b/compiler/plc_diagnostics/src/diagnostics/error_codes/E105.md
@@ -0,0 +1,12 @@
+# CONSTANT keyword in POU
+
+The `CONSTANT` keyword is not allowed for POU declarations, only variables can be `CONSTANT`
+
+Erroneous code example:
+```
+FUNCTION FOO : BOOL CONSTANT 
+VAR_INPUT
+END_VAR
+    // ...
+END_FUNCTION
+```
diff --git a/src/builtins.rs b/src/builtins.rs
@@ -35,7 +35,7 @@ lazy_static! {
         (
             "ADR",
             BuiltIn {
-                decl: "FUNCTION ADR<U: ANY> : LWORD
+                decl: "FUNCTION ADR<U: ANY> : LWORD CONSTANT
                 VAR_INPUT
                     in : U;
                 END_VAR
@@ -63,7 +63,7 @@ lazy_static! {
         (
             "REF",
             BuiltIn {
-                decl: "FUNCTION REF<U: ANY> : REF_TO U
+                decl: "FUNCTION REF<U: ANY> : REF_TO U CONSTANT
                 VAR_INPUT
                     in : U;
                 END_VAR

diff --git a/src/index.rs b/src/index.rs
@@ -457,6 +457,7 @@ pub enum PouIndexEntry {
         is_variadic: bool,
         location: SourceLocation,
         is_generated: bool, // true if this entry was added automatically (e.g. by generics)
+        is_const: bool,
     },
     Class {
         name: String,
@@ -529,6 +530,7 @@ impl PouIndexEntry {
         linkage: LinkageType,
         is_variadic: bool,
         location: SourceLocation,
+        is_const: bool,
     ) -> PouIndexEntry {
         PouIndexEntry::Function {
             name: name.into(),
@@ -538,6 +540,7 @@ impl PouIndexEntry {
             is_variadic,
             location,
             is_generated: false,
+            is_const,
         }
     }
 
@@ -550,6 +553,7 @@ impl PouIndexEntry {
         linkage: LinkageType,
         is_variadic: bool,
         location: SourceLocation,
+        is_const: bool,
     ) -> PouIndexEntry {
         PouIndexEntry::Function {
             name: name.into(),
@@ -559,6 +563,7 @@ impl PouIndexEntry {
             is_variadic,
             location,
             is_generated: true,
+            is_const,
         }
     }
 
@@ -752,6 +757,10 @@ impl PouIndexEntry {
         matches!(self, PouIndexEntry::Method { .. })
     }
 
+    pub(crate) fn is_constant(&self) -> bool {
+        matches!(self, PouIndexEntry::Function { is_const: true, .. })
+    }
+
     pub fn get_location(&self) -> &SourceLocation {
         match self {
             PouIndexEntry::Program { location, .. }

diff --git a/src/index/tests/index_tests.rs b/src/index/tests/index_tests.rs
@@ -1379,6 +1379,7 @@ fn a_program_pou_is_indexed() {
             is_variadic: false,
             location: source_location_factory.create_range(65..75),
             is_generated: false,
+            is_const: false,
         }),
         index.find_pou("myFunction"),
     );

diff --git a/src/index/visitor.rs b/src/index/visitor.rs
@@ -185,6 +185,7 @@ pub fn visit_pou(index: &mut Index, pou: &Pou) {
                 pou.linkage,
                 has_varargs,
                 pou.name_location.clone(),
+                pou.is_const,
             ));
             index.register_pou_type(datatype);
         }
@@ -206,6 +207,7 @@ pub fn visit_pou(index: &mut Index, pou: &Pou) {
                 pou.linkage,
                 has_varargs,
                 pou.name_location.clone(),
+                false,
             ));
             index.register_init_function(&pou.name);
             index.register_pou_type(datatype);

diff --git a/src/lowering/initializers.rs b/src/lowering/initializers.rs
@@ -315,6 +315,7 @@ fn new_pou(name: &str, variable_blocks: Vec<VariableBlock>, location: &SourceLoc
         generics: vec![],
         linkage: LinkageType::Internal,
         super_class: None,
+        is_const: false,
     }
 }
 

diff --git a/src/parser.rs b/src/parser.rs
@@ -199,6 +199,19 @@ fn parse_pou(
             // classes do not have a return type (check in validator)
             let return_type = parse_return_type(lexer, &pou_type);
 
+            // parse optional const specifier for const-builtins
+            let constant = lexer.try_consume(&KeywordConstant);
+            if constant && !matches!(linkage, LinkageType::BuiltIn) {
+                lexer.accept_diagnostic(
+                    Diagnostic::new("CONSTANT specifier is not allowed in POU declaration")
+                        .with_location(
+                            lexer
+                                .source_range_factory
+                                .create_range(lexer.last_range.start..lexer.last_range.end),
+                        )
+                        .with_error_code("E105"),
+                );
+            }
             // parse variable declarations. note that var in/out/inout
             // blocks are not allowed inside of class declarations.
             let mut variable_blocks = vec![];
@@ -247,6 +260,7 @@ fn parse_pou(
                 generics,
                 linkage,
                 super_class,
+                is_const: constant,
             }];
             pous.append(&mut impl_pous);
 
@@ -426,6 +440,16 @@ fn parse_method(
         let (name, name_location) = parse_identifier(lexer)?;
         let generics = parse_generics(lexer);
         let return_type = parse_return_type(lexer, &pou_type);
+        let constant = lexer.try_consume(&KeywordConstant);
+        if constant {
+            lexer.accept_diagnostic(
+                Diagnostic::new("CONSTANT specifier is not allowed in POU declaration")
+                    .with_location(
+                        lexer.source_range_factory.create_range(lexer.last_range.start..lexer.last_range.end),
+                    )
+                    .with_error_code("E105"),
+            );
+        }
 
         let mut variable_blocks = vec![];
         while lexer.token == KeywordVar
@@ -465,6 +489,7 @@ fn parse_method(
                 generics,
                 linkage,
                 super_class: None,
+                is_const: constant,
             },
             implementation,
         ))

diff --git a/src/parser/tests/expressions_parser_tests.rs b/src/parser/tests/expressions_parser_tests.rs
@@ -1597,6 +1597,7 @@ fn sized_string_as_function_return() {
         generics: vec![],
         linkage: LinkageType::Internal,
         super_class: None,
+        is_const: false,
     };
 
     assert_eq!(format!("{:?}", ast.units[0]), format!("{expected:?}"));
@@ -1639,6 +1640,7 @@ fn array_type_as_function_return() {
         generics: vec![],
         linkage: LinkageType::Internal,
         super_class: None,
+        is_const: false,
     };
 
     assert_eq!(format!("{:?}", ast.units[0]), format!("{expected:?}"));

diff --git a/src/parser/tests/function_parser_tests.rs b/src/parser/tests/function_parser_tests.rs
@@ -240,6 +240,7 @@ fn varargs_parameters_can_be_parsed() {
         generics: vec![],
         linkage: LinkageType::Internal,
         super_class: None,
+        is_const: false,
     };
     assert_eq!(format!("{expected:#?}"), format!("{x:#?}").as_str());
 }
@@ -310,6 +311,7 @@ fn sized_varargs_parameters_can_be_parsed() {
         generics: vec![],
         linkage: LinkageType::Internal,
         super_class: None,
+        is_const: false,
     };
     assert_eq!(format!("{expected:#?}"), format!("{x:#?}").as_str());
 }
@@ -520,3 +522,121 @@ fn var_input_by_ref_parsed() {
     }
     "###)
 }
+
+#[test]
+fn constant_keyword_can_be_parsed_but_errs() {
+    let src = r#"
+        FUNCTION_BLOCK foo CONSTANT END_FUNCTION_BLOCK
+        PROGRAM bar CONSTANT END_PROGRAM 
+        CLASS qux CONSTANT 
+            METHOD quux : DINT CONSTANT END_METHOD 
+        END_CLASS         
+        FUNCTION corge  : BOOL CONSTANT END_FUNCTION
+    "#;
+    let (_, diagnostics) = parse(src);
+
+    insta::assert_debug_snapshot!(diagnostics, @r###"
+    [
+        Diagnostic {
+            message: "CONSTANT specifier is not allowed in POU declaration",
+            primary_location: SourceLocation {
+                span: Range(
+                    TextLocation {
+                        line: 1,
+                        column: 27,
+                        offset: 28,
+                    }..TextLocation {
+                        line: 1,
+                        column: 35,
+                        offset: 36,
+                    },
+                ),
+            },
+            secondary_locations: None,
+            error_code: "E105",
+            sub_diagnostics: [],
+            internal_error: None,
+        },
+        Diagnostic {
+            message: "CONSTANT specifier is not allowed in POU declaration",
+            primary_location: SourceLocation {
+                span: Range(
+                    TextLocation {
+                        line: 2,
+                        column: 20,
+                        offset: 76,
+                    }..TextLocation {
+                        line: 2,
+                        column: 28,
+                        offset: 84,
+                    },
+                ),
+            },
+            secondary_locations: None,
+            error_code: "E105",
+            sub_diagnostics: [],
+            internal_error: None,
+        },
+        Diagnostic {
+            message: "CONSTANT specifier is not allowed in POU declaration",
+            primary_location: SourceLocation {
+                span: Range(
+                    TextLocation {
+                        line: 3,
+                        column: 18,
+                        offset: 116,
+                    }..TextLocation {
+                        line: 3,
+                        column: 26,
+                        offset: 124,
+                    },
+                ),
+            },
+            secondary_locations: None,
+            error_code: "E105",
+            sub_diagnostics: [],
+            internal_error: None,
+        },
+        Diagnostic {
+            message: "CONSTANT specifier is not allowed in POU declaration",
+            primary_location: SourceLocation {
+                span: Range(
+                    TextLocation {
+                        line: 4,
+                        column: 31,
+                        offset: 157,
+                    }..TextLocation {
+                        line: 4,
+                        column: 39,
+                        offset: 165,
+                    },
+                ),
+            },
+            secondary_locations: None,
+            error_code: "E105",
+            sub_diagnostics: [],
+            internal_error: None,
+        },
+        Diagnostic {
+            message: "CONSTANT specifier is not allowed in POU declaration",
+            primary_location: SourceLocation {
+                span: Range(
+                    TextLocation {
+                        line: 6,
+                        column: 31,
+                        offset: 236,
+                    }..TextLocation {
+                        line: 6,
+                        column: 39,
+                        offset: 244,
+                    },
+                ),
+            },
+            secondary_locations: None,
+            error_code: "E105",
+            sub_diagnostics: [],
+            internal_error: None,
+        },
+    ]
+    "###);
+}
diff --git a/src/resolver/const_evaluator.rs b/src/resolver/const_evaluator.rs
@@ -571,16 +571,20 @@ fn evaluate_with_target_hint(
         AstStatement::ParenExpression(expr) => {
             evaluate_with_target_hint(expr, scope, index, target_type, lhs)?
         }
-        AstStatement::CallStatement(plc_ast::ast::CallStatement { parameters, .. }) => {
-            let Some(arg) = parameters else {
+        AstStatement::CallStatement(plc_ast::ast::CallStatement { operator, .. }) => {
+            if let Some(pou) = operator.as_ref().get_flat_reference_name().and_then(|it| index.find_pou(it)) {
+                if !(pou.is_constant() && index.get_builtin_function(pou.get_name()).is_some()) {
+                    return Err(UnresolvableKind::Misc(format!(
+                        "Call-statement '{}' in initializer is not constant.",
+                        pou.get_name()
+                    )));
+                }
+            } else {
+                // POU not found
                 return Err(UnresolvableKind::Misc(format!("Cannot resolve constant: {:#?}", initial)));
             };
-            return match evaluate_with_target_hint(arg, scope, index, target_type, lhs) {
-                // arg to const fn call could not be found in the index => unresolvable (only ref/adr are supported for now, must have arg)
-                Ok(None) => Err(UnresolvableKind::Misc(format!("Cannot resolve constant: {arg:#?}"))),
-                // we found a local or global parameter for REF/ADR, but it cannot be resolved as constant since the address is not yet known. Resolve during codegen
-                _ => Err(UnresolvableKind::Address(InitData::new(Some(initial), target_type, scope, lhs))),
-            };
+
+            return Err(UnresolvableKind::Address(InitData::new(Some(initial), target_type, scope, lhs)));
         }
         _ => return Err(UnresolvableKind::Misc(format!("Cannot resolve constant: {initial:#?}"))),
     };

diff --git a/src/resolver/generics.rs b/src/resolver/generics.rs
@@ -149,6 +149,7 @@ impl<'i> TypeAnnotator<'i> {
                 LinkageType::External, //it has to be external, we should have already found this in the global index if it was internal
                 generic_function.is_variadic(),
                 generic_function.get_location().clone(),
+                generic_function.is_constant(),
             ));
 
             // register the member-variables (interface) of the new function