Don't use try-catch

Author: blegat

src/Utilities/matrix_of_constraints.jl

@@ -252,10 +252,11 @@ function modify_constants end
         row::Integer,
         col::Integer,
         new_coefficient,
-    )
+    )::Bool
 
 Modify `coefficients` in-place to store `new_coefficient` at position
-`(row, col)`.
+`(row, col)`. Return `true` if the entry existed and was modified, and `false`
+if no entry exists at `(row, col)` in the sparse structure and `new_coefficient` is nonzero.
 
 This function must be implemented to enable
 [`MOI.ScalarCoefficientChange`](@ref) for [`MatrixOfConstraints`](@ref).
@@ -719,15 +720,20 @@ function MOI.modify(
     ci::MOI.ConstraintIndex,
     change::MOI.ScalarCoefficientChange,
 )
-    try
-        modify_coefficients(
-            model.coefficients,
-            rows(model, ci),
-            change.variable.value,
-            change.new_coefficient,
+    if !modify_coefficients(
+        model.coefficients,
+        rows(model, ci),
+        change.variable.value,
+        change.new_coefficient,
+    )
+        throw(
+            MOI.ModifyConstraintNotAllowed(
+                ci,
+                change,
+                "cannot set a new non-zero coefficient because no entry " *
+                "exists in the sparse matrix of `MatrixOfConstraints`",
+            ),
         )
-    catch
-        throw(MOI.ModifyConstraintNotAllowed(ci, change))
     end
     return
 end

src/Utilities/sparse_matrix.jl

@@ -172,14 +172,9 @@ function modify_coefficients(
     r = _shift(row, OneBasedIndexing(), _indexing(A))
     if idx <= last(range) && A.rowval[idx] == r
         A.nzval[idx] = new_coefficient
-    elseif !iszero(new_coefficient)
-        error(
-            "Cannot set a new non-zero coefficient at ($row, $col) because " *
-            "no entry exists in the sparse matrix. Adding new entries to a " *
-            "`MutableSparseMatrixCSC` after `final_touch` is not supported.",
-        )
+        return true
     end
-    return
+    return iszero(new_coefficient)
 end
 
 """