Fix enforcement of const member access inside methods (#1945)

pkl-core/src/main/java/org/pkl/core/ast/builder/SymbolTable.java

@@ -357,8 +357,9 @@ public final class SymbolTable {
       var depth = -1;
       var lexicalScope = getLexicalScope();
       while (lexicalScope.getConstLevel() == ConstLevel.ALL) {
-        // LambdaScope inherits constLevel but doesn't create a const scope barrier
-        if (!(lexicalScope instanceof LambdaScope)) {
+        // LambdaScope inherits constLevel but doesn't create a const scope barrier.
+        // Method scopes don't level up.
+        if (!(lexicalScope instanceof LambdaScope) && !(lexicalScope instanceof MethodScope)) {
           depth += 1;
         }
         var parent = lexicalScope.getParent();

pkl-core/src/test/files/LanguageSnippetTests/input/errors/const/constMethod3.pkl

@@ -0,0 +1,5 @@
+x = 1
+
+const function f() = x
+
+r = f()

pkl-core/src/test/files/LanguageSnippetTests/input/errors/const/constMethod4.pkl

@@ -0,0 +1,5 @@
+obj {
+  x = 1
+  local const function f() = x
+  r = f()
+}

pkl-core/src/test/files/LanguageSnippetTests/input/errors/const/constMethod5.pkl

@@ -0,0 +1,5 @@
+const function a() = b()
+
+function b() = 3
+
+res = a()

pkl-core/src/test/files/LanguageSnippetTests/output/errors/const/constMethod3.err

@@ -0,0 +1,22 @@
+–– Pkl Error ––
+Cannot reference property `x` from here because it is not `const`.
+
+x | const function f() = x
+                         ^
+at constMethod3#f (file:///$snippetsDir/input/errors/const/constMethod3.pkl)
+
+To fix, do either of:
+1. Add modifier `const` to property `x`
+2. Self-import this module, and reference this property from the import.
+
+x | r = f()
+        ^^^
+at constMethod3#r (file:///$snippetsDir/input/errors/const/constMethod3.pkl)
+
+xxx | renderer.renderDocument(value)
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)
+
+xxx | if (renderer is BytesRenderer) renderer.renderDocument(value) else text.encodeToBytes("UTF-8")
+                                                                         ^^^^
+at pkl.base#Module.output.bytes (pkl:base)

pkl-core/src/test/files/LanguageSnippetTests/output/errors/const/constMethod4.err

@@ -0,0 +1,22 @@
+–– Pkl Error ––
+Cannot reference property `x` from here because it is not `const`.
+
+x | local const function f() = x
+                               ^
+at constMethod4#obj.f (file:///$snippetsDir/input/errors/const/constMethod4.pkl)
+
+To fix, do either of:
+1. Add modifier `const` to property `x`
+2. Self-import this module, and reference this property from the import.
+
+x | r = f()
+        ^^^
+at constMethod4#obj.r (file:///$snippetsDir/input/errors/const/constMethod4.pkl)
+
+xxx | renderer.renderDocument(value)
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)
+
+xxx | if (renderer is BytesRenderer) renderer.renderDocument(value) else text.encodeToBytes("UTF-8")
+                                                                         ^^^^
+at pkl.base#Module.output.bytes (pkl:base)

pkl-core/src/test/files/LanguageSnippetTests/output/errors/const/constMethod5.err

@@ -0,0 +1,22 @@
+–– Pkl Error ––
+Cannot call method `b` from here because it is not `const`.
+
+x | const function a() = b()
+                         ^^^
+at constMethod5#a (file:///$snippetsDir/input/errors/const/constMethod5.pkl)
+
+To fix, do either of:
+1. Add modifier `const` to method `b`
+2. Self-import this module, and reference this method from the import.
+
+x | res = a()
+          ^^^
+at constMethod5#res (file:///$snippetsDir/input/errors/const/constMethod5.pkl)
+
+xxx | renderer.renderDocument(value)
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+at pkl.base#Module.output.text (pkl:base)
+
+xxx | if (renderer is BytesRenderer) renderer.renderDocument(value) else text.encodeToBytes("UTF-8")
+                                                                         ^^^^
+at pkl.base#Module.output.bytes (pkl:base)