fix: prevent shadowing of trait consts by contract vars (#480)

CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Name clashes with FunC keywords in struct constructor function parameters: PR [#467](https://github.com/tact-lang/tact/issues/467)
 - Error messages for traversing non-path-expressions in `foreach`-loops : PR [#479](https://github.com/tact-lang/tact/pull/479)
+- Shadowing of trait constants by contract storage variables: PR [#480](https://github.com/tact-lang/tact/pull/480)
 
 ## [1.4.0] - 2024-06-21
 

src/types/__snapshots__/resolveDescriptors.spec.ts.snap

@@ -245,6 +245,16 @@ Line 9, col 24:
 "
 `;
 
+exports[`resolveDescriptors should fail descriptors for scope-storage-var-shadows-trait-const 1`] = `
+"<unknown>:8:3: Contract Foo inherits constant "storageReserve" from its traits and hence cannot have a storage variable with the same name
+Line 8, col 3:
+  7 |   // is a virtual constant defined in BaseTrait
+> 8 |   storageReserve: Int;
+        ^~~~~~~~~~~~~~~~~~~
+  9 | 
+"
+`;
+
 exports[`resolveDescriptors should fail descriptors for scope-struct-shadows-contract 1`] = `
 "<unknown>:12:1: Type "Main" already exists
 Line 12, col 1:

src/types/resolveDescriptors.ts

@@ -1402,6 +1402,14 @@ export function resolveDescriptors(ctx: CompilerContext) {
                         t.ast.ref,
                     );
                 }
+                const contractField = t.fields.find((v) => v.name === f.name);
+                if (contractField) {
+                    // a trait constant has the same name as a contract field
+                    throwCompilationError(
+                        `Contract ${t.name} inherits constant "${f.name}" from its traits and hence cannot have a storage variable with the same name`,
+                        contractField.ref,
+                    );
+                }
 
                 // Register constant
                 t.constants.push({

src/types/test-failed/scope-storage-var-shadows-trait-const.tact

@@ -0,0 +1,13 @@
+primitive Int;
+
+trait BaseTrait { virtual const storageReserve: Int = 0; }
+
+contract Foo {
+  // this should be a var-scope error because storageReserve
+  // is a virtual constant defined in BaseTrait
+  storageReserve: Int;
+
+  init() {
+    self.storageReserve = ton("0.05");
+  }
+}