@@ -1308,6 +1308,14 @@ function extractModUnit(modLoc: u64, exprVisitor: WasmExprVisitor): u32 {
   return extractModAttr(modLoc, "unit", exprVisitor);
 }
 
+function extractModStart(modLoc: u64, exprVisitor: WasmExprVisitor): u32 {
+  return extractModAttr(modLoc, "start", exprVisitor);
+}
+
+function extractModFixed(modLoc: u64, exprVisitor: WasmExprVisitor): u32 {
+  return extractModAttr(modLoc, "fixed", exprVisitor);
+}
+
 
 
 const MOD_ENTRY_SLOTS: u32 = 256;
@@ -4280,11 +4288,15 @@ export class ModelicaFlattener {
     }
 
     let declModLoc = findClassModificationLoc(modLoc);
+    let declStartId: u32 = 0xffffffff;
+    let declFixedId: u32 = 0xffffffff;
     if (!locIsNull(declModLoc)) {
       let declUnitId = extractModUnit(declModLoc, this.exprVisitor);
       if (declUnitId != 0xffffffff) {
         subtypeUnitId = declUnitId;
       }
+      declStartId = extractModStart(declModLoc, this.exprVisitor);
+      declFixedId = extractModFixed(declModLoc, this.exprVisitor);
     }
 
     if (this.scopeStackPtr != 0) {
@@ -4360,7 +4372,14 @@ export class ModelicaFlattener {
     }
 
     let startVal: f64 = 0.0;
-    if (valExprId != 0xffffffff) {
+    if (declStartId != 0xffffffff) {
+      let expr = ExprAccessor.at(this.dae.getExprData(), declStartId);
+      if (expr.kind == ExprKind.RealLiteral) {
+        startVal = expr.realValue;
+      } else if (expr.kind == ExprKind.IntLiteral) {
+        startVal = expr.intValue as f64;
+      }
+    } else if (valExprId != 0xffffffff) {
       let expr = ExprAccessor.at(this.dae.getExprData(), valExprId);
       if (expr.kind == ExprKind.RealLiteral) {
         startVal = expr.realValue;
@@ -4401,9 +4420,14 @@ export class ModelicaFlattener {
             }
           }
           let elemVarIdx = this.dae.addVariable(elemNameId, varType, variability, effectiveCausality, elemStartVal, varFlags);
-          if (elemExprId != 0xffffffff && isParamOrConst) {
+          if (declStartId != 0xffffffff) {
+            this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Start as u32, declStartId);
+          } else if (elemExprId != 0xffffffff && isParamOrConst) {
             this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Start as u32, elemExprId);
           }
+          if (declFixedId != 0xffffffff) {
+            this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Fixed as u32, declFixedId);
+          }
           if (subtypeUnitId != 0xffffffff) {
             this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Unit as u32, subtypeUnitId);
           }
@@ -4434,9 +4458,14 @@ export class ModelicaFlattener {
               }
             }
             let elemVarIdx = this.dae.addVariable(elemNameId, varType, variability, effectiveCausality, elemStartVal, varFlags);
-            if (elemExprId != 0xffffffff && isParamOrConst) {
+            if (declStartId != 0xffffffff) {
+              this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Start as u32, declStartId);
+            } else if (elemExprId != 0xffffffff && isParamOrConst) {
               this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Start as u32, elemExprId);
             }
+            if (declFixedId != 0xffffffff) {
+              this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Fixed as u32, declFixedId);
+            }
             if (subtypeUnitId != 0xffffffff) {
               this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Unit as u32, subtypeUnitId);
             }
@@ -4474,9 +4503,14 @@ export class ModelicaFlattener {
                 }
               }
               let elemVarIdx = this.dae.addVariable(elemNameId, varType, variability, effectiveCausality, elemStartVal, varFlags);
-              if (elemExprId != 0xffffffff && isParamOrConst) {
+              if (declStartId != 0xffffffff) {
+                this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Start as u32, declStartId);
+              } else if (elemExprId != 0xffffffff && isParamOrConst) {
                 this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Start as u32, elemExprId);
               }
+              if (declFixedId != 0xffffffff) {
+                this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Fixed as u32, declFixedId);
+              }
               if (subtypeUnitId != 0xffffffff) {
                 this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Unit as u32, subtypeUnitId);
               }
@@ -4486,10 +4520,15 @@ export class ModelicaFlattener {
         }
       } else {
         let isParamOrConst = variability == (Variability.Parameter as i32) || variability == (Variability.Constant as i32);
-        let varIdx = this.dae.addVariable(fullVarNameId, varType, variability, effectiveCausality, isParamOrConst ? startVal : 0.0, varFlags);
-        if (valExprId != 0xffffffff && isParamOrConst) {
+        let varIdx = this.dae.addVariable(fullVarNameId, varType, variability, effectiveCausality, (isParamOrConst || declStartId != 0xffffffff) ? startVal : 0.0, varFlags);
+        if (declStartId != 0xffffffff) {
+          this.dae.setVarAttrExpr(varIdx, VarAttrKind.Start as u32, declStartId);
+        } else if (valExprId != 0xffffffff && isParamOrConst) {
           this.dae.setVarAttrExpr(varIdx, VarAttrKind.Start as u32, valExprId);
         }
+        if (declFixedId != 0xffffffff) {
+          this.dae.setVarAttrExpr(varIdx, VarAttrKind.Fixed as u32, declFixedId);
+        }
         if (subtypeUnitId != 0xffffffff) {
           this.dae.setVarAttrExpr(varIdx, VarAttrKind.Unit as u32, subtypeUnitId);
         }
 
@@ -1318,6 +1318,99 @@ export const ModelicaErrorCode = {
     message: (newPrefix: string, compName: string, existingPrefix: string) =>
       `Invalid type prefix '${newPrefix}' on component ${compName}, due to existing type prefix '${existingPrefix}'.`,
   },
+  SAME_NAME_TYPE_SHADOWING: {
+    code: 2011,
+    rule: "same-name-type-shadowing",
+    severity: "error",
+    message: (typeSpec: string) => `Found a component with same name when looking for type ${typeSpec}.`,
+  },
+  ATTRIBUTE_TYPE_MISMATCH: {
+    code: 3015,
+    rule: "attribute-type-mismatch",
+    severity: "error",
+    message: (varName: string, attrName: string, actualType: string, expectedType: string) =>
+      `Variable ${varName}: Wrong type on builtin attribute ${attrName} (type was: ${actualType}, expected: ${expectedType}).`,
+  },
+  CONDITIONAL_TYPE_MISMATCH: {
+    code: 3016,
+    rule: "conditional-type-mismatch",
+    severity: "error",
+    message: (condExpr: string, actualType: string) =>
+      `Type error in conditional '${condExpr}'. Expected Boolean, got ${actualType}.`,
+  },
+  CONNECT_TYPES_INCONSISTENT: {
+    code: 3017,
+    rule: "connect-types-inconsistent",
+    severity: "error",
+    message: (r0Raw: string, type0: string, r1Raw: string, type1: string) =>
+      `The type of variables \n${r0Raw} type:\n${type0} and \n${r1Raw} type:\n${type1}\nare inconsistent in connect equations.`,
+  },
+  RECURSIVE_DEFINITION: {
+    code: 4058,
+    rule: "recursive-definition",
+    severity: "error",
+    message: (elemName: string, className: string) =>
+      `Declaration of element ${elemName} causes recursive definition of class ${className}.`,
+  },
+  MAX_RECURSION_DEPTH_EXCEEDED: {
+    code: 4059,
+    rule: "max-recursion-depth-exceeded",
+    severity: "error",
+    message: (depth: string = "256") =>
+      `The maximum recursion depth of ${depth} was reached, probably due to mutually recursive definitions.`,
+  },
+  IMPLICIT_ITERATOR_SUBSCRIPT_MISSING: {
+    code: 5025,
+    rule: "implicit-iterator-subscript-missing",
+    severity: "error",
+    message: (iterName: string) =>
+      `Identifier ${iterName} of implicit for iterator must be present as array subscript in the loop body.`,
+  },
+  IMPLICIT_ITERATION_DIM_MISMATCH: {
+    code: 5026,
+    rule: "implicit-iteration-dim-mismatch",
+    severity: "error",
+    message: (dim1: string, name1: string, dim2: string, name2: string) =>
+      `Dimension ${dim1} of ${name1} and ${dim2} of ${name2} differs when trying to deduce implicit iteration range.`,
+  },
+  WHEN_CONDITION_NOT_DISCRETE: {
+    code: 5027,
+    rule: "when-condition-not-discrete",
+    severity: "error",
+    message: (condText: string) => `When-condition '${condText}' is not a discrete-time expression.`,
+  },
+  WHEN_IF_BRANCH_LHS_MISMATCH: {
+    code: 5028,
+    rule: "when-if-branch-lhs-mismatch",
+    severity: "error",
+    message: () =>
+      "The branches of an if-equation inside a when-equation must have the same set of component references on the left-hand side.",
+  },
+  CLOCKED_WHEN_HAS_ELSEWHEN: {
+    code: 5029,
+    rule: "clocked-when-has-elsewhen",
+    severity: "error",
+    message: () => "Clocked when equation can not contain elsewhen part.",
+  },
+  CLOCKED_WHEN_BRANCH_IN_WHEN: {
+    code: 5030,
+    rule: "clocked-when-branch-in-when",
+    severity: "error",
+    message: () => "Clocked when branch in when equation.",
+  },
+  INVALID_WHEN_LHS: {
+    code: 5031,
+    rule: "invalid-when-lhs",
+    severity: "error",
+    message: (lhsStr: string) => `Invalid left-hand side of when-equation: ${lhsStr}.`,
+  },
+  WHEN_CONDITIONAL_EXPECTED_BOOLEAN: {
+    code: 5032,
+    rule: "when-conditional-expected-boolean",
+    severity: "error",
+    message: (condStr: string) =>
+      `Type error in when conditional '${condStr}'. Expected Boolean scalar or vector, got Clock.`,
+  },
 } as const satisfies Record<string, ErrorCodeDef>;
 
 // Derive the union type of all error code keys
Original file line number	Diff line number	Diff line change
`@@ -1308,6 +1308,14 @@ function extractModUnit(modLoc: u64, exprVisitor: WasmExprVisitor): u32 {`
`1308`	`1308`	`return extractModAttr(modLoc, "unit", exprVisitor);`
`1309`	`1309`	`}`
`1310`	`1310`
	`1311`	`+function extractModStart(modLoc: u64, exprVisitor: WasmExprVisitor): u32 {`
	`1312`	`+ return extractModAttr(modLoc, "start", exprVisitor);`
	`1313`	`+}`
	`1314`	`+`
	`1315`	`+function extractModFixed(modLoc: u64, exprVisitor: WasmExprVisitor): u32 {`
	`1316`	`+ return extractModAttr(modLoc, "fixed", exprVisitor);`
	`1317`	`+}`
	`1318`	`+`
`1311`	`1319`
`1312`	`1320`
`1313`	`1321`	`const MOD_ENTRY_SLOTS: u32 = 256;`
`@@ -4280,11 +4288,15 @@ export class ModelicaFlattener {`
`4280`	`4288`	`}`
`4281`	`4289`
`4282`	`4290`	`let declModLoc = findClassModificationLoc(modLoc);`
	`4291`	`+ let declStartId: u32 = 0xffffffff;`
	`4292`	`+ let declFixedId: u32 = 0xffffffff;`
`4283`	`4293`	`if (!locIsNull(declModLoc)) {`
`4284`	`4294`	`let declUnitId = extractModUnit(declModLoc, this.exprVisitor);`
`4285`	`4295`	`if (declUnitId != 0xffffffff) {`
`4286`	`4296`	`subtypeUnitId = declUnitId;`
`4287`	`4297`	`}`
	`4298`	`+ declStartId = extractModStart(declModLoc, this.exprVisitor);`
	`4299`	`+ declFixedId = extractModFixed(declModLoc, this.exprVisitor);`
`4288`	`4300`	`}`
`4289`	`4301`
`4290`	`4302`	`if (this.scopeStackPtr != 0) {`
`@@ -4360,7 +4372,14 @@ export class ModelicaFlattener {`
`4360`	`4372`	`}`
`4361`	`4373`
`4362`	`4374`	`let startVal: f64 = 0.0;`
`4363`		`- if (valExprId != 0xffffffff) {`
	`4375`	`+ if (declStartId != 0xffffffff) {`
	`4376`	`+ let expr = ExprAccessor.at(this.dae.getExprData(), declStartId);`
	`4377`	`+ if (expr.kind == ExprKind.RealLiteral) {`
	`4378`	`+ startVal = expr.realValue;`
	`4379`	`+ } else if (expr.kind == ExprKind.IntLiteral) {`
	`4380`	`+ startVal = expr.intValue as f64;`
	`4381`	`+ }`
	`4382`	`+ } else if (valExprId != 0xffffffff) {`
`4364`	`4383`	`let expr = ExprAccessor.at(this.dae.getExprData(), valExprId);`
`4365`	`4384`	`if (expr.kind == ExprKind.RealLiteral) {`
`4366`	`4385`	`startVal = expr.realValue;`
`@@ -4401,9 +4420,14 @@ export class ModelicaFlattener {`
`4401`	`4420`	`}`
`4402`	`4421`	`}`
`4403`	`4422`	`let elemVarIdx = this.dae.addVariable(elemNameId, varType, variability, effectiveCausality, elemStartVal, varFlags);`
`4404`		`- if (elemExprId != 0xffffffff && isParamOrConst) {`
	`4423`	`+ if (declStartId != 0xffffffff) {`
	`4424`	`+ this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Start as u32, declStartId);`
	`4425`	`+ } else if (elemExprId != 0xffffffff && isParamOrConst) {`
`4405`	`4426`	`this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Start as u32, elemExprId);`
`4406`	`4427`	`}`
	`4428`	`+ if (declFixedId != 0xffffffff) {`
	`4429`	`+ this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Fixed as u32, declFixedId);`
	`4430`	`+ }`
`4407`	`4431`	`if (subtypeUnitId != 0xffffffff) {`
`4408`	`4432`	`this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Unit as u32, subtypeUnitId);`
`4409`	`4433`	`}`
`@@ -4434,9 +4458,14 @@ export class ModelicaFlattener {`
`4434`	`4458`	`}`
`4435`	`4459`	`}`
`4436`	`4460`	`let elemVarIdx = this.dae.addVariable(elemNameId, varType, variability, effectiveCausality, elemStartVal, varFlags);`
`4437`		`- if (elemExprId != 0xffffffff && isParamOrConst) {`
	`4461`	`+ if (declStartId != 0xffffffff) {`
	`4462`	`+ this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Start as u32, declStartId);`
	`4463`	`+ } else if (elemExprId != 0xffffffff && isParamOrConst) {`
`4438`	`4464`	`this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Start as u32, elemExprId);`
`4439`	`4465`	`}`
	`4466`	`+ if (declFixedId != 0xffffffff) {`
	`4467`	`+ this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Fixed as u32, declFixedId);`
	`4468`	`+ }`
`4440`	`4469`	`if (subtypeUnitId != 0xffffffff) {`
`4441`	`4470`	`this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Unit as u32, subtypeUnitId);`
`4442`	`4471`	`}`
`@@ -4474,9 +4503,14 @@ export class ModelicaFlattener {`
`4474`	`4503`	`}`
`4475`	`4504`	`}`
`4476`	`4505`	`let elemVarIdx = this.dae.addVariable(elemNameId, varType, variability, effectiveCausality, elemStartVal, varFlags);`
`4477`		`- if (elemExprId != 0xffffffff && isParamOrConst) {`
	`4506`	`+ if (declStartId != 0xffffffff) {`
	`4507`	`+ this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Start as u32, declStartId);`
	`4508`	`+ } else if (elemExprId != 0xffffffff && isParamOrConst) {`
`4478`	`4509`	`this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Start as u32, elemExprId);`
`4479`	`4510`	`}`
	`4511`	`+ if (declFixedId != 0xffffffff) {`
	`4512`	`+ this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Fixed as u32, declFixedId);`
	`4513`	`+ }`
`4480`	`4514`	`if (subtypeUnitId != 0xffffffff) {`
`4481`	`4515`	`this.dae.setVarAttrExpr(elemVarIdx, VarAttrKind.Unit as u32, subtypeUnitId);`
`4482`	`4516`	`}`
`@@ -4486,10 +4520,15 @@ export class ModelicaFlattener {`
`4486`	`4520`	`}`
`4487`	`4521`	`} else {`
`4488`	`4522`	`let isParamOrConst = variability == (Variability.Parameter as i32) \|\| variability == (Variability.Constant as i32);`
`4489`		`- let varIdx = this.dae.addVariable(fullVarNameId, varType, variability, effectiveCausality, isParamOrConst ? startVal : 0.0, varFlags);`
`4490`		`- if (valExprId != 0xffffffff && isParamOrConst) {`
	`4523`	`+ let varIdx = this.dae.addVariable(fullVarNameId, varType, variability, effectiveCausality, (isParamOrConst \|\| declStartId != 0xffffffff) ? startVal : 0.0, varFlags);`
	`4524`	`+ if (declStartId != 0xffffffff) {`
	`4525`	`+ this.dae.setVarAttrExpr(varIdx, VarAttrKind.Start as u32, declStartId);`
	`4526`	`+ } else if (valExprId != 0xffffffff && isParamOrConst) {`
`4491`	`4527`	`this.dae.setVarAttrExpr(varIdx, VarAttrKind.Start as u32, valExprId);`
`4492`	`4528`	`}`
	`4529`	`+ if (declFixedId != 0xffffffff) {`
	`4530`	`+ this.dae.setVarAttrExpr(varIdx, VarAttrKind.Fixed as u32, declFixedId);`
	`4531`	`+ }`
`4493`	`4532`	`if (subtypeUnitId != 0xffffffff) {`
`4494`	`4533`	`this.dae.setVarAttrExpr(varIdx, VarAttrKind.Unit as u32, subtypeUnitId);`
`4495`	`4534`	`}`